BEHAVIORAL
RESPONSES OF LYNX
TO
DECLINING SNOWSHOE HARE ABUNDANCE
by
RICHARD M.P.WARD
B.Sc.
Acadia Univ.
Nova S c o t i a 1978
A THESIS SUBMITTED I N PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
in
THE FACULTY OF GRADUATE STUDIES
(Department of Zoology)
We a c c e p t t h i s t h e s i s a s c o n f o r m i n g
required standard
to the
THE UNIVERSITY OF B R I T I S H COLUMBIA
J a n u a r y 1985
(?)
R i c h a r d M.P.Ward, 1985
In p r e s e n t i n g
this
thesis i n partial
f u l f i l m e n t of the
r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e
of B r i t i s h Columbia, I agree that
it
freely
t h e L i b r a r y s h a l l make
a v a i l a b l e f o r r e f e r e n c e and s t u d y .
agree t h a t p e r m i s s i o n f o r extensive
for
University
s c h o l a r l y p u r p o s e s may
for
financial
of
The U n i v e r s i t y o f B r i t i s h
1956 Main M a l l
V a n c o u v e r , Canada
V6T 1Y3
DE-6
(3/81)
Columbia
my
It is
thesis
s h a l l n o t be a l l o w e d w i t h o u t my
permission.
Department
thesis
be g r a n t e d by t h e h e a d o f
copying or p u b l i c a t i o n of t h i s
gain
further
copying of t h i s
d e p a r t m e n t o r by h i s o r h e r r e p r e s e n t a t i v e s .
understood that
I
written
i i
ABSTRACT
The
behavioral
responses
of lynx
(Lynx
canadensis) t o
d e c l i n e s i n snowshoe h a r e
(Lepus a m e r i c a n u s ) abundance
were
examined
i n the southwestern
Yukon.
B e t w e e n A p r i l 1982 a n d
J u n e 1984 11 l y n x were r a d i o - t a g g e d
and m o n i t o r e d
w i t h i n and
near
t h e K l u a n e Game S a n c t u a r y .
L y n x mean home r a n g e s i z e
i n c r e a s e d f r o m 13.2 t o 39.2 km c o n c u r r e n t
with
a decline i n
snowshoe h a r e a b u n d a n c e f r o m 14.7 t o 0.2 h a r e s / h a .
Below about
0.5 h a r e s / h a s e v e r a l l y n x a b a n d o n e d t h e i r home r a n g e s a n d became
nomadic, a l t h o u g h
they remained w i t h i n the g e n e r a l study area.
T r a c k t r a n s e c t s t h r o u g h a r e a s known t o have d i f f e r e n t
snowshoe
hare
d e n s i t i e s indicated that,lynx concentrated their foraging
e f f o r t s i n areas of r e l a t i v e l y
high
snowshoe h a r e
abundance.
Lynx abandoned t h e s e a r e a s a f t e r hare abundance d e c l i n e d .
Lynx
foraging
e f f o r t i n t e r m s o f d i s t a n c e t r a v e l l e d p e r d a y showed a
c u r v i l i n e a r r e l a t i o n s h i p t o snowhoe h a r e a b u n d a n c e .
Straightline
daily
travel
distance
remained
constant
a t 2.2 t o 2.7'
km/day a b o v e 1.0 h a r e / h a .
Below
1.0 h a r e s / h a ,
straight-line
d a i l y t r a v e l d i s t a n c e s i n c r e a s e d r a p i d l y , r e a c h i n g 5.5 km/day a t
0.2 h a r e s / h a .
T h r e e o f 7 r a d i o - t a g g e d l y n x d i s p e r s e d 250 km o r
more
from
the study area d u r i n g t h e p e r i o d of r a p i d d e c l i n e i n
h a r e a b u n d a n c e i n 1982.
No s i m i l a r l o n g d i s t a n c e d i s p e r s a l was
recorded
after
hare
densities stablized
a t l e s s than
1.0
hares/ha.
T r a p p i n g m o r t a l i t y was r e s p o n s i b l e f o r t h e l o s s o f 7
of
9
radio-tagged
lynx
that
travelled
outside
t h e game
sanctuary.
One l y n x d i e d , a n d i s b e l i e v e d
t o have
starved,
d u r i n g t h e w i n t e r o r s p r i n g o f 1984.
The h i g h r a t e o f t r a p p i n g
mortality
outside
t h e game s a n c t u a r y s u g g e s t s t h a t r e f u g i a i n
wilderness areas are important i n m a i n t a i n i n g
lynx
populations
d u r i n g p e r i o d s of low r e c r u i t m e n t .
2
TABLE OF CONTENTS
ABSTRACT
i i
L I S T OF TABLES
iv
L I S T OF FIGURES
v
ACKNOWLEDGEMENTS . .
vi
INTRODUCTION
1
METHODS a n d STUDY AREA
5
Study Area
5
T i m i n g and Emphasis o f Study
5
E s t i m a t i o n o f Snowshoe H a r e A b u n d a n c e
8
Lynx T r a p p i n g and R a d i o T a g g i n g
9
R a d i o T e l e m e t r y a n d Home Range D e t e r m i n a t i o n
9
Track Transects
11
RESULTS
12
Snowshoe H a r e A b u n d a n c e
12
Lynx T r a p p i n g Success
15
Effect
o f Snowshoe
Hare
Abundance on L y n x Home Range
Size
21
E f f e c t o f Snowshoe
Hare
A b u n d a n c e on L y n x
Foraging
Effort
35
Effect
o f Snowshoe
H a r e D i s t r i b u t i o n on L y n x F o r a g i n g
Patterns
. 38
Lynx
Dispersal
and M o r t a l i t y
during
a Decline
in
Snowshoe H a r e A b u n d a n c e
44
DISCUSSION
49
L y n x Home Range S i z e
49
Effect
o f Snowshoe
Hare
A b u n d a n c e on Lynx F o r a g i n g
Effort
56
E f f e c t o f Snowshoe H a r e D i s t r i b u t i o n
on L y n x
Foraging
Patterns
66
Lynx D i s p e r s a l and M o r t a l i t y
68
Lynx S o c i a l S t r u c t u r e
72
Management I m p l i c a t i o n s
76
Introduction
76
The M o d e l s
77
R e s u l t s and D i s c u s s i o n
82
REFERENCES CITED
95
APPENDIX
102
L I S T OF
TABLES
T a b l e 1. Summary o f t h e i m p o r t a n c e o f snowshoe h a r e s i n t h e
d i e t of l y n x
3
T a b l e 2. Summary o f l y n x t r a p p i n g s u c c e s s
16
T a b l e 3. L y n x body w e i g h t s
18
Table
4.
Comparison
of
100% a n d 90% home r a n g e a r e a s o f
lynx
24
T a b l e 5. E f f e c t o f r e l a t i v e snowshoe h a r e a b u n d a n c e on l y n x
foraging patterns
42
Table
6.
Parameter
e s t i m a t e s used
i n lynx
population
s i m u l a t i o n models
78
V
L I S T OF FIGURES
F i g u r e 1. Map o f s t u d y a r e a
F i g u r e 2. Snowshoe h a r e a b u n d a n c e
Figure
3. E x a m p l e s
o f 100% a n d 9 0 % l y n x home r a n g e s i z e
estimates
F i g u r e 4. Mean home r a n g e s i z e
f o r lynx
versus
snowshoe
hare abundance
Figure
5. I n d i v i d u a l l y n x home r a n g e s i z e s v e r s u s snowshoe
hare abundance
F i g u r e 6. Map o f a r e a s
delineated
by j o i n i n g
outermost
o b s e r v e d l o c a t i o n s of "nomadic" i n d i v i d u a l s
F i g u r e 7. Mean s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e s o f l y n x
v e r s u s snowshoe h a r e a b u n d a n c e
Figure
8. Maximum o b s e r v e d
straight-line
daily
travel
d i s t a n c e s o f l y n x v e r s u s snowshoe h a r e a b u n d a n c e
Figure
9. Map o f l o n g
distance
dispersal
movements
u n d e r t a k e n by l y n x
Figure
10. O b s e r v e d
and expected
total
daily
travel
d i s t a n c e s f o r l y n x v e r s u s snowshoe h a r e a b u n d a n c e
F i g u r e 11. R e p r o d u c t i o n o f F i g u r e 2, B r a n d a n d K e i t h ( 1 9 7 9 )
w i t h 2 a d d i t i o n a l r e g r e s s i o n l i n e s added
F i g u r e 12. D y n a m i c s o f s i m u l a t e d
lynx
population
using
model A w i t h o b s e r v e d m o r t a l i t y r a t e s
Figure
13. D y n a m i c s o f s i m u l a t e d
lynx population using
model A w i t h t o t a l a n n u a l m o r t a l i t y r a t e s e t a t 0.30. ..
F i g u r e 14. D y n a m i c s o f s i m u l a t e d
lynx
population
using
model A a n d m o r t a l i t y
rate
e s t i m a t e s from Brand and
K e i t h 1979
6
13
22
26
29
32
36
39
46
59
62
83
85
87
vi
ACKNOWLEDGEMENTS
Many i n d i v i d u a l s made v a l u a b l e c o n t r i b u t i o n s t o my p r o g r e s s
in t h i s study.
Foremost, I wish to d e d i c a t e t h i s t h e s i s to
the
11 i n d i v i d u a l s w i t h o u t whose i n v o l v e m e n t t h i s r e s e a r c h w o u l d n o t
have
been p o s s i b l e : To J o y , S c r u f f , S i d , C h a r l e y , C a r l o s , J e a n ,
S c o t t i e , Rene, J e n n i f e r , E n r i q u e and P a u l .
Dr.
C.J.
K r e b s was t h e p r i n c i p l e a c a d e m i c s u p e r v i s o r f o r
this
study.
Throughout
the
study,
he
p r o v i d e d s u p p o r t and
encouragement i n v a r i o u s forms.
He a l s o s e t an
inspiring,
if
exhausting,
example w i t h
the
amount
of e n e r g y he d e v o t e d t o
f i e l d r e s e a r c h and e c o l o g y i n g e n e r a l . T h a n k s a g a i n C h a r l e y .
Dr.
A.R.E. S i n c l a i r a l s o a c t e d
as
academic
supervisor
during
a p o r t i o n of
this
study.
He
also provided o f f i c e
s u p p l i e s d u r i n g the w r i t e - u p phase of the s t u d y .
T h a n k s Tony.
I gratefully
acknowledge
the
support
and
input
of
my
research
committee.
Drs.
C.J.
K r e b s , J.N.M. S m i t h and
D.M.
S h a c k l e t o n a l l made v a l u a b l e comments and u s e f u l s u g g e s t i o n s .
I w i s h t o e x p r e s s my a p p r e c i a t i o n t o t h e
staff
and
other
r e s e a r c h e r s a t t h e K l u a n e L a k e R e s e a r c h S t a t i o n who made my s t a y
there
an
extremely
p l e a s a n t and r e w a r d i n g t i m e .
I especially
w i s h t o thank the 2 W i l l i a m s
families,
S c o t t , Jean,
Carlos,
Jennifer,
J o y and J o h n .
I t w o u l d n ' t h a v e been t h e same w i t h o u t
you.
When n o t p l a y i n g w i t h g r i z z l y b e a r s d u r i n g
the
summer
of
1983,
Henrik
Asfelt
assisted
i n data
collection.
Alistair
B l a c h f o r d and Tom H u r d a s s i s t e d w i t h
the
computer
programming
necessary
f o r data
analysis.
Tom
Hurd
a l s o made v a l u a b l e
comments on an i n i t i a l d r a f t .
Marc L a b e l l e o f f e r e d a d v i c e
on
statistical analysis.
O t h e r s , t o o numerous t o name, a s s i s t e d i n
various
aspects
of
this
r e s e a r c h . To them I o f f e r my s i l e n t
gratitude.
T h i s r e s e a r c h was f u n d e d by g r a n t s
from
British
Columbia
Science
C o u n c i l , Northern
Scientific
T r a i n i n g Program,
and
g r a n t s t o Dr.
Charles
Krebs
from
the
Natural
Sciences
and
E n g i n e e r i n g Research C o u n c i l .
1
INTRODUCTION
The c l o s e r e l a t i o n s h i p b e t w e e n t h e t e n y e a r c y c l e s o f
(Lynx
canadensis)
first
noted
a n d t h e snowshoe h a r e
i n the e c o l o g i c a l l i t e r a t u r e
(1942).
Since
ecology
h a v e been
studied
In
of
review).
then
view
many
snowshoe h a r e numbers,
lynx
1973,
Nava
Keith
an
increase
in
lynx
has
et a l .
a l .
1983
for a
of the previous
et a l .
de J o n g
1963,
1972, B r a n d e t a l .
1983).
work
Stewart
1976, B r a n d
T h e s e s t u d i e s have
m o r t a l i t y and a d e c l i n e
also
et
have r e l a t e d h a r e a b u n d a n c e t o
and m o r t a l i t y (van Z y l l
w i t h d e c l i n i n g snowshoe
of
of l y n x n a t u r a l h i s t o r y and
(see Parker
however,
1979, P a r k e r
Nicholson
t o snowshoe h a r e a b u n d a n c e .
1970, N e l l i s
and
by E l t o n a n d
surprisingly l i t t l e
studies,
reproduction
( L e p u s a m e r i c a n u s ) was
t h e c l o s e r e l a t i o n s h i p between l y n x and
has r e l a t e d l y n x e c o l o g y
Several
aspects
lynx
hare abundance.
i n recruitment
G e n e r a l body
b e e n shown t o be p o s i t i v e l y
shown
of l y n x
condition
correlated with
hare abundance.
Studies
of
lynx
Nellis
o f t h e e f f e c t s o f h a r e a b u n d a n c e on
ecology
et a l .
s t u d i e s were
population
Parker
and
been r e p o r t e d
1972, N e l l i s
part
dynamics
et a l .
of
a
in
by N e l l i s
long
Alberta
term
study
(Keith
of
and
diet
These
snowshoe
hare
of
1978).
prey
abundance
have been u n a n i m o u s
in finding
i n Nova S c o t i a .
studies
of
1976.
Windberg
and
others
t h a t snowshoe h a r e s a r e t h e s i n g l e most i m p o r t a n t
the
aspects
a n d K e i t h 1968,
1975, a n d B r a n d e t a l .
( 1 9 8 3 ) a l s o r e p o r t on a s t u d y
lynx ecology
These
have
other
the
lynx
food
item
d u r i n g a l l p h a s e s o f t h e 10 y e a r
in
cycle
2
(Table
1).
mortality
The
rates
indicates that
decline
fact
and
that
lynx
recruitment
declines
i n c r e a s e w i t h d e c l i n i n g hare abundance
lynx are
low
severely
energy
stressed
p h a s e s of t h e h a r e c y c l e .
One
and
clearly
during
would
the
therefore
expect that
l y n x would e x h i b i t major b e h a v i o r a l
changes
effort
continue
requirements
to
to f u l f i l l
hare abundance d e c l i n e s .
use
are:
1)
foraging
effort
increase
effort
In t h i s
study
utilize
each
energy
intake.
during
a
structuring
of
most o b v i o u s m e c h a n i s m s l y n x
home r a n g e s i z e ;
3)
and
seek out
r e l a t i v e l y high
I
investigated
these
possible
I present
data
snowshoe
hare
the
social
i m p l i c a t i o n s o f my
energetic
their
and
i n p a t c h e s of
The
their
lynx
in
f i n d i n g s are
on
2)
increase
concentrate
prey
the
their
an
as
might
their
foraging
abundance.
degree
to
which
lynx
mechanisms t o maximize
their
lynx d i s p e r s a l
decline.
system
discussed.
and
Finally,
and
the
mortality
the
factors
management
3
Table
1.
A summary f r o m p a s t s t u d i e s o f t h e i m p o r t a n c e
snowshoe h a r e s i n t h e d i e t o f l y n x .
of
Study
Nellis
et a l .
1 972
Alberta
Brand
et a l .
1976
Alberta
More
1 976
southwestern
N.W.T.
van Z y l l
De J o n g
1 963
Alberta
Saunders
1 963
Nfld.
Hare
cycle
phase
decline
Season
winters
1964-67
Most
important
item i n
lynx diet
hares
7 6% o f
biomass
N e x t most
important
item i n
lynx d i e t
9.8%
carrion
low
winter
carrion
52% o f
biomass
high
winter
hares
100% o f
biomass
high
summer
hares
91% of
biomass
2% m i c e
and v o l e s
low
winter
hares
79-100%
f r e q . of
occurance
in scats
25-64%
red
squirrel
winter
hares
79% f r e q .
of o c c u r ,
i n gut
contents
10%
microtine
summer
hares
52% f r e q .
of o c c u r ,
in gut
contents
31%
microtine
winter
hares
85% o f
b i oma s s
summer
hares
60% o f
biomass
start
of
decline
hares
43% of
biomass
1 3%
moose
30%
microtine
5
METHODS AND STUDY AREA
Study
The
Kluane
s t u d y was c e n t e r e d
National
Management
Park
Zone
Area
i n the southwestern
within
and
adjacent
Yukon, n o r t h of
to
of the northern b o r e a l f o r e s t
(1974).
White
species,
The
spruce
study area
roads
accomplished
by
glauca)
i s t h e dominant
i s d i s s e c t e d by a number o f o l d m i n i n g
which
facilitated
snowmobile,
Timing
I conducted
February
travel.
snowshoeing
and
Winter
skiing.
1982 a n d J u n e 1984.
a n d May 1982 I f o c u s e d my e f f o r t s
around
trapping
l y n x a n d snowshoe h a r e s
each
grid.
f o r both
Winter
After
Summer
and Emphasis of Study
t h e s t u d y between F e b r u a r y
during this period.
and
b i k e and w a l k i n g .
Pond) ( F i g u r e 1 ) . I e x p e n d e d
on
less
t r a v e l was
A (Microwave) and B (Beaver
effort
is
tree
s p p . ) and o t h e r
was by f o u r w h e e l d r i v e t r u c k , t r a i l
Between
area
s p e c i e s m a k i n g up t h e u n d e r s t o r y .
exploration
travel
(Picea
The
zone a s d e s c r i b e d by D o u g l a s
with a v a r i e t y of willows (Salix
abundant shrubs
Game
6-10 ( F i g u r e 1 ) . T h i s i s c l a s s i f i e d a s a game
s a n c t u a r y w i t h no h u n t i n g o r t r a p p i n g p e r m i t t e d .
part
Yukon
snow-tracking
on e a c h
e f f o r t was a l s o
grids
equal
grid
equal
May 1982, g r i d B was a b a n d o n e d f o r l y n x
t r a p p i n g and s n o w - t r a c k i n g
due t o i t s
relative
inaccessibility
6
Figure
1.
Map o f s t u d y a r e a i n s o u t h w e s t e r n Y u k o n .
A, B, C
and D i n d i c a t e l o c a t i o n s o f snowshoe h a r e l i v e - t r a p p i n g
grids.
See t e x t f o r a d e s c r i p t i o n o f t h e g r i d s .
8
although
I
L y n x and
within
continued
in
Game S a n c t u a r y
this
distribution
an
monitor
h a r e a b u n d a n c e on t h e
snowshoe h a r e m o n i t o r i n g c o n t i n u e d t o be most
the Kluane
system
to
area.
t o t a k e a d v a n t a g e of
Careful
records
of
the
grid.
intensive
the
road
number
of l y n x t r a c k s i n t h e s a n c t u a r y were k e p t
and
so
that
e s t i m a t e c o u l d be made o f t h e p r o p o r t i o n of l y n x i n t h e
t h a t were r a d i o - t a g g e d .
necessary
The
total
study area
was
area
expanded
as
to maintain c o n t a c t w i t h the r a d i o - t a g g e d lynx ( F i g u r e
1).
E s t i m a t i o n o f Snowshoe H a r e A b u n d a n c e
Snowshoe h a r e a b u n d a n c e was
grids
in
on
determine
the
Grid A
effect
Grids B
(Beaver
for
( F i g u r e 1).
Pond), C
d e s c r i b e d by B o u t i n
of s u p p l e m e n t a l
f o o d on h a r e
( G r i z z l y ) and
D
(1050)
(1980).
alive
H a r e a b u n d a n c e was
t h e g r i d s were c a l c u l a t e d w i t h o u t
discussed
the b i a s i n t r o d u c e d i n t o d e n s i t y
relatively
H i s model s u g g e s t s
to 3 times too high.
grid).
determined
1966).
are
using
Hare
t h e a d d i t i o n of a
estimates
size
to
controls
Bondrup-Nielsen
small grid
t h a t my
grid
these g r i d s
(Krebs
strip
of
of
method
boundry
programs.
(MNA/area
(MNA)
their
abundance.
were
L i v e - t r a p p i n g t e c h n i q u e s on
d e n s i t i e s on
use
s t u d y of
a food a d d i t i o n
number
the
live-trapping
( M i c r o w a v e ) was
t h e minimum
from
four
t h e s t u d y a r e a a s p a r t of a c o n c u r r e n t
ten year c y c l e .
A
monitored
(1983)
resulting
in live-trapping
d e n s i t y e s t i m a t e s may
be
2
9
L y n x T r a p p i n g and
Radio
T r a p p i n g e f f o r t s t o c a p t u r e and
from
February
1983.
t r a p s but
similar
(see
from A p r i l
f r o m #2
trappers.
t o #4,
(concentration
trapped, i t
I00mg/ml:
padded
i n "cubby" type
and
fitted
sets
roads
once e v e r y 24
hours.
l u r e s t o perfume
was
immoblized
and
rogar/STB,
division
with
ketaset
o f BTI
Products
L o n d o n , O n t a r i o ) a t a d o s a g e o f a p p r o x i m a t e l y 0.2
kg o f body w e i g h t .
were
used.
Once a l y n x was
Inc.,
at least
box
Steel leg-
w i t h the jaws
of b a i t s r a n g i n g from c o m m e r c i a l
r i b b o n s were
t o September
S e t s were p l a c e d a l o n g t r a i l s
t h e s t u d y a r e a and c h e c k e d
variety
continued
Later trapping efforts
t o t h o s e e m p l o y e d by p r o f e s s i o n a l
ranging i n size
lynx
made t o c a p t u r e l y n x u s i n g
ineffective.
Anonymous,1982).
silver
and
was
and
e i t h e r c l o t h t a p e o r r u b b e r were u s e d
within
A
, an a t t e m p t
t h i s proved
hold traps,
with
radio-tag
t h r o u g h December 1982
Initially
Tagging
The
l y n x was
then weighed,
with a radio transmitter
prior
to
sexed,
ml
per
ear-tagged
release.
R a d i o T e l e m e t r y and Home Range D e t e r m i n a t i o n
Radio
Materials
standard
telemetry
equipment
Inc., Carbondale,
radio-telemetry
c o m b i n a t i o n of h a n d h e l d
checks
on
bearings
transmitters
using
this
and
was
Illinois.
L y n x were
techniques
fixed
produced
(Cochran
tower
i n known l o c a t i o n s
system
by
Wildlife
located
1980)
antennas.
using
with
a
Accuracy
indicated that
were a c c u r a t e t o + 5 d e g r e e s
compass
95% o f
10
the
time.
tagged
Compass b e a r i n g s
animal
was f e l t t h a t t h e e r r o r
no
compass b e a r i n g s
were
disappeared
using
at
was
required
from t h e study
radio-telemetry
various
accurate
was a c t i v e when t h e b e a r i n g
it
bearings
were l e s s
times
introduced
recorded.
to
was
June
of
minimum
each l o c a t i o n .
an e f f o r t
I f a lynx
was made t o l o c a t e i t
The l y n x
t h e day and n i g h t
were
located
from A p r i l and
1984. Once f i t t e d w i t h a r a d i o t r a n s m i t t e r , e a c h
lynx
until
month
i t dispersed
trappers,
I defined
following
compass
May
followed
3
2
1983 a n d d u r i n g
professional
a
If
A
December, 1982 a n d b e t w e e n May a n d O c t o b e r ,
and
taken.
was e x c e s s i v e ,
f r o m an a i r c r a f t .
throughout
was b e i n g
radio-
by a c t i v i t y
produce
area,
i f the
from t h e a r e a ,
i t was t r a p p e d
or the t r a n s m i t t e r stopped
working.
home r a n g e a s t h e c o n s i s t e n t u s e o f an a r e a
period.
I therefore
3 month p e r i o d s
subdivided
by
t h e study
over
into the
f o r subsequent a n a l y s i s :
MONTHS
PERIOD
A p r i l - J u n e 1982
2
J u l y - S e p t e m b e r 1982
3
O c t o b e r - D e c e m b e r 1982
4
A p r i l - J u n e 1983
5
J u l y - S e p t e m b e r 1983
6
A p r i l - J u n e 1984
I u s e d a minimum o f 30 p o i n t
to
determine
home r a n g e .
l o c a t i o n s w i t h i n . each
period
Home r a n g e s i z e was e s t i m a t e d
by t h e
11
convex
polygon
method
modification.
I
(Mohr
eliminated
1947)
with
t h e outermost
the
following
10% o f l o c a t i o n s i n
c a l c u l a t i n g home r a n g e s i z e a f t e r t h e method o f B o u t i n
This
the
reduced
assessment
the i n c l u s i o n of o c c a s i o n a l
wanderings
(1980).
by l y n x i n
o f i t s home r a n g e .
Track T r a n s e c t s
To
determine
abundance
transects
on p a t t e r n s
The
e v e r y 600 m e t e r s
permitted
effects
of
of h a b i t a t
relative
each
number
of
throughout
December 1982.
April
have
of s e t s of f r e s h l y n x
transect
morning
snowshoe
u s e by l y n x , w i n t e r
were r u n t h r o u g h a r e a s known t o
abundances.
conducted
the
was
when
and
recorded.
weather
from
and
late
hare
snow
track
different
hare
tracks
crossing
Transects
snow
October
were
conditions
to
early
12
RESULTS
Snowshoe
Hare
Abundance
H a r e a b u n d a n c e on g r i d s A ( s u p p l e m e n t a l f o o d g r i d ) , C and D
peaked
in
i n the f a l l
the f a l l
1981
on
of 1980.
o f 1981.
grid
A
Maximum f a l l
(Figure
10.3,
2).
8.0
monitoring lynx
on g r i d A h a r e d e n s i t y
density
had
dropped
control grids
Population
and
o f 1982.
was
3.3
on
levelled
(mean
0.2
±0.1
slightly,
densities
hares/ha.
relatively
I
h a r e a b u n d a n c e on g r i d s B,
C,
(mean
2.1
±0.5)
14.7 h a r e s / h a .
the
1.0 ±0.4
1982
By
o f f or increased
grids
July
food
hares/ha.
Snowshoe
t h r o u g h June
1984.
hare
grid.
slightly
on a l l
born.
a g a i n on a l l
on a l l g r i d s a t
hare
r e m a i n e d r e l a t i v e l y c o n s t a n t a t b e t w e e n 0.2 a n d 0.5
all
hares/ha
h a r e s / h a on t h e
supplemental
i n 1983 were e q u i v a l e n t
±0.2
high
when
and 1.4
In A p r i l
By J u l y d e n s i t i e s on a l l g r i d s h a d
a v e r a g i n g 0.5
±1.2)
r a p i d l y on
t h e summer months a s y o u n g o f t h e y e a r were
Spring
in
B, C and D
9.7
to decline
D u r i n g O c t o b e r , h o w e v e r , d e n s i t i e s began t o d e c l i n e
grids.
density
densities
on g r i d s
remaining
to approximately
to
densites
grids during
hare
10.7
began
activities,
D r e s p e c t i v e l y was 2.6, 2.4
while
and
1982 w h i l e
on g r i d A t h r o u g h o u t t h e s p r i n g
and
snowshoe
Densities
g r i d s B, C a n d D i n J a n u a r y
began
B r e a c h e d i t s maximum
were 22.6 h a r e s / h a , w h i l e
t h e y were r e s p e c t i v e l y
hares/ha
Grid
increased
densities
hares/ha
on
13
Figure
2.
Snowshoe h a r e d e n s i t y on s u p p l e m e n t a l f o o d g r i d A
( s o l i d l i n e ) and c o n t r o l g r i d s B, C a n d D ( d a s h e d l i n e ) .
D e n s i t i e s a r e b a s e d on t o t a l e n u m e r a t i o n t e c h n i q u e s
( K r e b s 1966)..
V e r t i c a l b a r s on d a s h e d l i n e i n d i c a t e ±1
standard deviation.
30i
January
1981
January
1982
DATE
January
1983
January
1984
15
Lynx T r a p p i n g
Eleven
tagged
lynx
(5 f e m a l e s
i n approximately
September
1983
Success
and 6 m a l e s ) were t r a p p e d and
4700 t r a p - n i g h t s b e t w e e n A p r i l
(Table 2 ) .
I n a d d i t i o n , one
r e c a p t u r e d and r e l e a s e d a p p r o x i m a t e l y
female
radio-
1982 and
(Jean)
9 months a f t e r h e r
was
initial
capture.
It
was
not
possible
i n d i v i d u a l s but from
it
was
evident
t o determine
t h e p r e c i s e age o f t h e
t h e c o n d i t i o n of t h e n i p p l e s and
t h a t two o f t h e f e m a l e s
( J o y and J e n n i f e r ) had
b r e d p r e v i o u s l y a n d were t h e r e f o r e a t l e a s t
showed
and
no
2 years o l d .
of p r e v i o u s b r e e d i n g but her weight
t h e f a c t t h a t she was t r a v e l l i n g a l o n e ,
was
also
initial
With
at
(10.7 kg)
suggests
that
S c r u f f and Rene showed no
and may
signs
of
developed
alone,
indicating
scrotal
testes
and
t h a t t h e y were a t l e a s t
a d u l t body w e i g h t ,
scrotal
were
b u t an i n c o m p l e t e l y d e v e l o p e d
travelling
body c o n d i t o n more r a p i d l y
(Table 3 ) .
appeared
to
lynx,
of 2 m a l e s c a p t u r e d l a t e
h i g h e r than
presumably
1982.
w o u l d seem t o l o s e
than males as hare abundance d e c l i n e s
A l l m a l e s c a p t u r e d and r a d i o - t a g g e d
be e x c e l l e n t
Scottie
p e n i s , non-
h i s m o t h e r , s u g g e s t i n g t h a t he was a young o f t h e y e a r
the l i m i t e d data o b t a i n e d , females
them.
weights,
1 year o l d .
t e s t e s a n d was t r a v e l l i n g w i t h a n o t h e r
From
of her
have been y e a r l i n g s when I r a d i o - t a g g e d
penises,
she
previous
t h e e x c e p t i o n of S c o t t i e , a l l m a l e s h a d a d u l t body
fully
Jean,
l e a s t one a n d a h a l f y e a r s o l d a t t h e t i m e
capture.
breeding
had
signs
genitalia
body c o n d i t i o n .
i n the
those captured e a r l y
study
in
this
I n f a c t body
were
i n the study.
equivalent
study
weights
to
or
Females captured
16
T a b l e 2.
Summary o f l y n x t r a p p i n g s u c c e s s , minimum r e s i d e n c y
t i m e on s t u d y a r e a and f a t e o f r a d i o - t a g g e d l y n x .
17
Lynx
Capture
date
(D/M/YR)
Joy
4/4/82
adult
=>2 y r s .
F
Sid
17/4/82
adult
=>1 y r .
M
9 Months
k i l l e d w i t h i n 10 km
of t a g g i n g s i t e ,
J a n u a r y 1983.
Scruff
21/4/82
adult
=>1 y r .
F
7 Months
d i s p e r s e d 16/10/82.
k i l l e d 250 km N
of t a g g i n g s i t e ,
Nov. 1982.
Charlie
25/5/82
adult
=>1 y r .
M
40 Days
d i s p e r s e d 5/7/82.
k i l l e d 250 km N
of t a g g i n g s i t e ,
D e c . 1982.
Carlos
1/8/82
adult
=>1 y r .
M
13 M o n t h s
r e s i d i n g i n study
a r e a S e p t e m b e r 1 983.
Scott ie
20/10/82
kitten
< 1 yr.
M
2 Months
k i l l e d w i t h i n 10 km
of t a g g i n g s i t e ,
December 1982.
Jean
25/10/82
adult
=>1 y r .
F
10 M o n t h s
k i l l e d w i t h i n 10 km
of t a g g i n g s i t e ,
w i n t e r 1983-84.
Rene
15/7/83
adult
=>1 y r .
F
6 Months
J e n n i f e r 19/7/83
adult
=>2 y r s .
F
11 M o n t h s
r e s i d i n g i n study
a r e a , J u n e 1984.
Enrique
29/7/83
adult
=>1 y r .
M
11 M o n t h s
r e s i d i n g i n study
a r e a , J u n e 1984:
Paul
1/8/83
adult
=>1 y r .
M
4 Months
Age
Sex
Minimum
residency
on s t u d y
area
35 Days
Fate
d i s p e r s e d 8/5/82.
k i l l e d 700 km
N of t a g g i n g s i t e ,
December 1982.
f o u n d d e a d 35 km
east of tagging
s i t e , J u n e 1984.
k i l l e d w i t h i n 10 km
of t a g g i n g s i t e ,
J a n u a r y 1984.
18
T a b l e 3.
Body w e i g h t s f o r i n d i v i d u a l l y n x a t t i m e o f
capture.
Means a r e n o t s i g n i f i c a n t l y d i f f e r e n t
P> 0 . 0 5 ) .
* indicates recapture.
(T-test
Date
April
to
December
1 982
April
to
September
1 983
Male c a p t u r e
w e i g h t s (Kg)
Sid
8.8
Charlie
8.6
Carlos
8.3
Scottie
9.7
mean = 8.9
95% c . i . = 8.0-9.7
Enrique
Paul
10.4
9.5
mean
=10.0
95% c . i . = 8.0-11 .9
Female c a p t u r e
w e i g h t s (Kg)
Joy
Scruff
Jean
9.5
8.3
lb.6
mean = 9.5
95% c . i . = 7.3-11.6
Jean *
9.9
Rene
7.7
J e n n i f e r 7.5
mean = 8.4
95% c . i . = 5.9-10.8
20
early
and
in
the
s t u d y h a d body w e i g h t s
a p p e a r e d t o be i n good c o n d i t i o n .
the
study
lower
(Rene
recapture
t o those of males
Those c a p t u r e d
later
a n d J e n n i f e r ) h o w e v e r , were e m a c i a t e d
body w e i g h t s .
body w e i g h t )
similar
Jean
also lost
between h e r i n i t i a l
and had
0.8 kg ( 7 . 5 % o f h e r
capture
i n October
in
initial
1982 a n d h e r
i n J u l y 1983.
Although
i t
is difficult
to
assess
accurately
what
p r o p o r t i o n o f t h e p o p u l a t i o n I h a d r a d i o - t a g g e d , an e s t i m a t e c a n
be o b t a i n e d , f o r t h e
t r a n s e c t s through
of
5
lynx
using
winters
the area.
at
least,
from
that
that
is
1).
track
I b e l i e v e t h a t I had r a d i o - t a g g e d 4
grid A in April
a n d May 1982.
mentioned, I expanded t o study a r e a d u r i n g t h e
(Figure
repeated
As p r e v i o u s l y
summer
of
1982
By November I was m o n i t o r i n g 5 l y n x a n d I s u s p e c t
5 more l y n x were r e s i d i n g
in.the
area.
Further
evidence
a l a r g e p r o p o r t i o n o f t h e l y n x p o p u l a t i o n was r a d i o - t a g g e d
that only
During
locations
1 o f 10 l y n x s i g h t e d d u r i n g t h e s t u d y was u n t a g g e d .
t h e 26 months o f
and
visual
Minimum r e s i d e n c y t i m e s
months.
the
sightings
f o r these
study,
were
over
made
l y n x ranged
1300
on
from
telemetry
t h e 11 l y n x .
35 d a y s t o 13
21
Effect
o f Snowshoe H a r e A b u n d a n c e on Lynx Home Range
As d e s c r i b e d
of
i n t h e m e t h o d s , I e l i m i n a t e d t h e o u t e r m o s t 10%
l o c a t i o n s when c a l c u l a t i n g
l y n x home r a n g e s i z e .
these outermost p o i n t s r e s u l t s
of
w i t h o t h e r s t u d i e s I p r e s e n t my r e s u l t s a s
ranges
(Table
4)
The l o s s o f
i n a r e d u c t i o n o f home r a n g e
f r o m 3 t o 70 p e r c e n t ( F i g u r e 3 a , b, c a n d d ) .
home
Size
both
and I use 90% range
size
For comparison
100%
and
90%
i n my a n a l y s i s a n d
discussion.
A l t h o u g h t h e r e was a
smaller
hare
home r a n g e s t h a n m a l e s
densities,
significant
for
i t was
(t-test,
During
consistently
the
or
have
statistically
The d a t a a r e t h e r e f o r e
of
snowshoe
summer
of
1983
Rene
Enrique
hare
combined
abundance
d i d not
also
on
u s e any a r e a
d i d not
a n a l y s i s would
o f home r a n g e a n d a r e t h e r e f o r e
a n a l y s i s of the e f f e c t
home r a n g e s i z e .
Including these
use
areas
through
the
increase
home r a n g e s i z e
in
the
Throughout
i n t h e s i z e of t h e i r
from
following
trend.
( F i g u r e 2 ) , hare d e n s i t i e s
e a r l y phases
i n the study.
omitted
o f h a r e a b u n d a n c e on l y n x
movements
strengthen the observed
As p r e v i o u s l y d i s c u s s e d
steady
to
d u r i n g t h e s p r i n g o f 1984. T h e s e movements do n o t
following
rate later
consistent
P>0.05).
J e n n i f e r and
my d e f i n i t i o n
rapidly
f o r females
size.
the
consistently.
trend
w i t h i n a g i v e n r a n g e o f snowshoe
not
the a n a l y s i s of t h e e f f e c t
l y n x home r a n g e
fit
slight
declined'
of t h e study and a t a l e s s e r
this decline,
home
lynx
ranges.
f o r a l l i n d i v i d u a l s a t d i f f e r e n t hare
showed a
Both
mean
abundances
( F i g u r e 4) a n d home r a n g e s o f i n d i v i d u a l s m o n i t o r e d t h r o u g h t i m e
22
F i g u r e 3.
E x a m p l e s o f 100% ( s o l i d l i n e ) a n d 90% ( d a s h e d
l i n e ) home r a n g e e s t i m a t e s .
F i g u r e 3a,b a n d c
r e p r e s e n t t h e home r a n g e o f S i d a t h a r e d e n s i t i e s o f
14.7, 3.3 a n d 2.2 h a r e s / h a r e s p e c t i v e l y .
F i g u r e 3d
r e p r e s e n t s t h e home r a n g e o f C a r l o s a t 0.5 h a r e s / h a .
24
T a b l e 4.
C o m p a r i s o n o f 100% a n d 9 0 % home r a n g e a r e a s o f
lynx.
Snowshoe h a r e d e n s i t i e s a r e i n i t i a l d e n s i t i e s a t
t h e s t a r t o f e a c h 3 month p e r i o d f o r w h i c h i n d i v i d u a l
l y n x home r a n g e s were c a l c u l a t e d .
L y n x home r a n g e s a r e
in square kilometers.
* i n d i c a t e s that area not
d e f i n e d a s a home r a n g e .
See t e x t f o r e x p l a n a t i o n .
Number o f l o c a t i o n s u s e d t o d e t e r m i n e e a c h home r a n g e i s
in parentheses.
25
Lynx
Hare
density
(hares/Ha)
100% home
range s i z e
(km )
2
90% home
range s i z e
(km )
2
Percent
di f ference
Joy
14.7
12.0 ( 3 0 )
7.3 ( 2 7 )
39
Sid
14.7
3.3
2.2
33.4 ( 9 5 )
104.3 ( 7 8 )
41.7 ( 5 3 )
13.3 ( 8 5 )
31.0 ( 7 0 )
27.9 ( 4 7 )
60
70
33
Scruff
14.7
i .3
46.4 ( 6 1 )
44.9 ( 6 3 )
17.7 ( 5 4 )
43.4 ( 5 6 )
62
3
Charlie
14.7
29.7 ( 5 4 )
14.6 ( 4 8 )
51
Carlos
1 .3
1 .0
0.5
0.2
28.8 ( 4 5 )
22.4 ( 4 6 )
113.9 ( 6 9 )
76.8 ( 8 5 )
15.8
16.1
58.1
52.4
(40)
(41)
(62)
(76)
45
28
49
32
Jean
1 .0
0.5
0.2
17.1 ( 3 1 )
68.5 ( 6 5 )
34.0 ( 9 7 )
13.7 ( 2 8 )
30.3 ( 5 8 )
28.1 ( 8 7 )
20
56
17
Scottie
1 .0
55.4 ( 3 4 )
27.6 (31 )
50
Jennifer
0.5
0.2
61.8 ( 5 0 )
200.6* (7)
33.5 ( 4 5 )
46
Rene
0.5
524.8 ( 3 1 )
254.7* (28)
51
Enrique
0.5
0.2
49.2 ( 5 5 )
69.6* ( 1 2 )
17.8 ( 4 9 )
64
Paul
0.5
86.7 ( 6 1 )
53.9 ( 5 4 )
38
26
Figure
4.
Mean home r a n g e s i z e f o r l y n x r e s i d i n g i n a r e a s
w i t h i n d i c a t e d snowshoe h a r e d e n s i t i e s .
Hare d e n s i t y
i s t h e i n i t i a l d e n s i t y a t t h e s t a r t o f e a c h 3 month
p e r i o d f o r w h i c h home r a n g e s o f i n d i v i d u a l l y n x were
calculated.
V e r t i c a l b a r s i n d i c a t e 95% c o n f i d e n c e
l i m i t s o f mean.
60-1
0.0
1.0, ^ 5A
^
-0.9 -4.9
-15.0
c
INITIAL HARE DENSITY
MNA/Ha
28
(Figure
5)
showed
this
plotted against either
for
each
three
the
variance
therefore
and
gave
This
t r e n d was s i m i l a r when
h a r e d e n s i t i e s o r mean
Using i n i t i a l
clearer
trends.
densities
These
as a f u n c t i o n of i n i t i a l
and
June
1982, t h e
grid A (early April
mean home r a n g e
4
hare d e n s i t y
s i z e o f 13.2 ( 9 5 % c . i .
8.8 t o 17.6) km .
2
the grid declined.
density
on
grid A declined at a different
mean home r a n g e
densities
i n the 2 areas i n
in
hares/ha.
were
the
increase
area
not a s i g n i f i c a n t
densities
larger
14.5 t o 35.7) km .
i n home
with
an
range
initial
23.7 t o 54.7) km .
2
1.0
and
4.9
hare
over
lynx
densities
Although
t o the o v e r a l l
abundance
declined,
still
this
i n areas with
i s
hare
hares/ha, i t i s s i g n i f i c a n t l y
w i t h h a r e d e n s i t e s g r e a t e r t h a n 4.9 h a r e s / h a
as
size
h a r e d e n s i t y o f 14.7
increase over lynx r e s i d i n g
between
addition
This
2
t h a n t h e mean home r a n g e s i z e o f l y n x r e s i d i n g
In
different
1.0 h a r e s / h a mean l y n x home r a n g e s i z e was
h i g h e r a t 39.2 ( 9 5 % c . i .
as
Lynx r e s i d i n g i n
D u r i n g t h e l o w p a r t o f t h e h a r e c y c l e when
l e s s than
ranges
b e t w e e n 1.0 a n d 4.9 h a r e s / h a h a d a
s i z e o f 25.1 ( 9 5 % c . i .
not a s i g n i f i c a n t
home
These
B e c a u s e h a r e d e n s i t i e s on
t i m e p e r i o d s a r e l u m p e d b a s e d on h a r e d e n s i t y .
hare
lynx
r a t e t h a n s u r r o u n d i n g a r e a s , home
range d a t a f o r i n d i v i d u a l s r e s i d i n g
residing
are
14.7 h a r e s / h a ) h a d a
hare
is
results
radio-tagged
d i s p e r s e d o r expanded t h e i r
with
reduced
hare d e n s i t i e s i n
individuals either
areas
densities
period.
Between A p r i l
utilizing
initial
month p e r i o d .
presented
e a c h 3 month
trend.
(t-test,
in
areas
P<0.05)
t r e n d t o w a r d s l a r g e r home r a n g e s
individual
lynx monitored through
29
Figure
5.
9 0 % home r a n g e s i z e s o f i n d i v i d u a l l y n x a t
i n d i c a t e d snowshoe h a r e d e n s i t y .
Hare d e n s i t y i s t h e
i n i t i a l d e n s i t y a t t h e s t a r t o f e a c h 3 month p e r i o d f o r
w h i c h home r a n g e were c a l c u l a t e d .
•
•
A
o
•
•
JOY
SID
SCRUFF
CHARLIE
CARLOS
JEAN
v
+
A
x
SCOTTIE
JENNIFER
ENRIQUE
PAUL
D
0
5
10
SNOWSHOE HARE DENSITY
HARES/Ha
15
31
more t h a n
size
to
one
increased
their
as hare abundance d e c l i n e d ( F i g u r e 5 ) .
this
Sid,
t r e n d was
a slight
decrease
The
home
decline
i n the f a l l
of
1982.
i n t h e home
With
range
observed
either
tendency
f o r i n d i v i d u a l s or
for
monitored,
A
during
female
the
(Rene),
i d e n t i f i e d a s h e r home r a n g e
in late July
1983,
she
to
2.2
slight
travelling
river
on
this
initial
tagging area.
before
disappearing
Within
She
for
this
several
p e r i o d she
occasions.
consistently
s u m m a t i o n of t h e
and
December
1983,
study
to
be
being
On
the
her
area
she
identified
to
an
as
area
located approximately
she
late
km
week
travelled
t o t h e SE
any
on
area
home r a n g e ,
for
her
255
35
a
September.
use
of
next
flowing
for
her
locations
radio-
r e t u r n e d t o the
return,
not
to
several
fast
area
until
did
for
a
a month she had
in
enough
S d u r i n g the
and
and
extensively in
After
35 km
a
and
radio-tagged
travelled
streams
90% o f my
amounts
she was
home r a n g e s
t r a v e l l e d a s much a s 25
innermost
October,
I
(Figure 6).
remained
Although
enough
1983,
4 days.
w i d e l y w i t h i n the general
was
t h e r e a p p e a r s t o be
that
approximately
crossed several large
trek.
season
remained i n the area
She
During
with
u s e d no a r e a c o n s i s t e n t l y
week.
July
of
in general.
hares/ha
summer of
the g e n e r a l study area but
before
size
some i n d i v i d u a l s t o abandon t h e i r
become n o m a d i c .
days
3.3
the e x c e p t i o n of the
range
A t d e n s i t i e s b e l o w a b o u t 0.5
tagged
size
i n t h e home r a n g e s i z e o f S i d a f t e r a p r e v i o u s i n c r e a s e ,
t r e n d t o w a r d s c h a n g e s i n home
be
range
only exception
c o n c u r r e n t w i t h a d e c l i n e i n hare abundance from
hares/ha
no
3 month t i m e p e r i o d
km
km .
2
E
a
between
In
of
mid
the
32
F i g u r e 6.
Map o f a r e a s d e l i n e a t e d by j o i n i n g o u t e r m o s t
o b s e r v e d l o c a t i o n s of "nomadic" i n d i v i d u a l s .
34
initial
r a d i o - t a g g i n g s i t e and I b e l i e v e she s t a r v e d d u r i n g t h e
previous
winter.
She was f o u n d d e a d i n t h i s a r e a
In a d d i t i o n , J e n n i f e r and E n r i q u e
1983,
had m a i n t a i n e d
widely
during
maintain
a
June
1984
were
that
their
Ninety
within
2
have
Based
d u r i n g t h e same
on
200 km
28.3)
than
No
over
These
areas
-21.7 t o 7 4 . 6 ) ,
considerably
Over t h e c o u r s e
10.5 ( 9 5 % c . i .
0.6 t o
a n d 22.0 ( 9 5 % c . i .
M a l e - m a l e o v e r l a p was
overlap
(t-test
15.7
significant
a l s o no s i g n i f i c a n t
significantly
on a r c s i n
difference
was
m a l e - m a l e a n d f e m a l e - f e m a l e home r a n g e o v e r l a p
was
wandered
f o r male-male, f e m a l e - f e m a l e and m a l e - f e m a l e
male-female
d a t a , P=0.04).
this
fully.
home r a n g e o v e r l a p a v e r a g e d
percent
locations,
during
2
period.
and between s e x e s t h r o u g h o u t t h e s t u d y .
interactions respectively.
and
7
home r a n g e s o f l y n x o v e r l a p p e d
24.5 ( 9 5 % c . i .
so
been l a r g e r i f i t h a d been p o s s i b l e t o
movements more
percent
of t h e s t u d y ,
There
travelling
i t was i m p o s s i b l e t o
t o t a l area of a t l e a s t
o f 60 km
undoubtedly
monitor
less
home r a n g e s ,
( F i g u r e 6 ) . B a s e d on 12 l o c a t i o n s , E n r i q u e
would
to
who, d u r i n g t h e summer o f
c o n t a c t w i t h them.
covered
a minimum a r e a
20.5),
and
continuous
Jennifer
period
May
distinct
i n J u n e 1984.
found
(t-test
d i f f e r e n c e between
f e m a l e - m a l e home r a n g e o v e r l a p
(t-test
transformed
between
P=0.18).
female-female
P=0.70).
L y n x home r a n g e o v e r l a p r e m a i n e d h i g h t h r o u g h o u t t h e
and
an
was
area.
relatively
(95% c . i .
not a f f e c t e d s i g n i f i c a n t l y
Overlap
high
by a b s o l u t e h a r e d e n s i t y i n
f o r the 4 i n d i v i d u a l s occupying
hare
abundance
16.0 t o 33.5) p e r c e n t .
study
the
area
of
( 1 4 . 7 h a r e s / h a ) a v e r a g e d 24.8
Between
July
and
September
35
1983
h a r e d e n s i t y on my f o u r g r i d s was a b o u t 0.5 h a r e s / h a .
range
overlap
for 5
l y n x r e s i d i n g i n an a d j a c e n t
t h i s p e r i o d was 20.5 ( 9 5 % c . i .
not
a significant
P=0.67).
Based
13.9 t o 27.1) p e r c e n t .
difference (t-test
on snow t r a c k i n g I am c o n f i d e n t
i n t h e s e two a r e a s r a d i o - t a g g e d
time
Home r a n g e o v e r l a p
This
-1.0
t o 26.4).
sharing
overlap
at
individuals
high
degree
a l l hare d e n s i t i e s , although
assumed
as
estimated
(DTD).
a
of
home
that
lynx
are
foraging
d i d Brand e t a l .
(1976).
by t h e s t r a i g h t - l i n e d i s t a n c e
Effort
whenever
they
Lynx f o r a g i n g
travelled
I c a l c u l a t e d t h i s by m e a s u r i n g t h e d i s t a n c e
L y n x showed no s i g n i f i c a n t c h a n g e i n t h e i r
a t snowshoe h a r e d e n s i t i e s a b o v e a b o u t
km).
range
v a r i a t i o n i n degree of
effort
p e r day
days.
foraging
1.0 h a r e s / h a
are
between t h e
p o i n t s where an i n d i v i d u a l was l o c a t e d on c o n s e c u t i v e
At
and low
(mean 1 5 . 3 , 9 5 % c . i .
o f Snowshoe H a r e Abundance on Lynx F o r a g i n g
travelling
was
indicates
two
b e t w e e n i n d i v i d u a l s was h i g h .
Effect
I
This
data,
i n these
f o r radio-tagged
r a n g e d f r o m 0.0 t o 36.9 p e r c e n t
is
t h a t I had t h e
m o n i t o r e d a t hare d e n s i t i e s between t h e s e extreme h i g h
densities
during
on a r c s i n t r a n s f o r m e d
majority of lynx
periods.
area
Home
effort
(Figure 7 ) .
14.7 h a r e s / h a l y n x mean DTD was 2.7 km ( 9 5 % c . i .
A t .1.0 h a r e s / h a l y n x h a d a mean DTD o f 2.4 km
1.8 t o 3.7
( 9 5 % c.. i .
2.0 t o 2.9 km).
Below about
DTD
rapidly
1.0 h a r e s / h a , h o w e v e r , l y n x
with d e c l i n i n g hare d e n s i t y .
increase
t h e i r mean
At hare d e n s i t i e s of
36
F i g u r e 7.
Mean s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e o f l y n x
v e r s u s snowshoe h a r e a b u n d a n c e .
Travel distances are
t h e mean f o r a l l i n d i v i d u a l s a t t h e i n d i c a t e d h a r e
density.
V e r t i c a l b a r s i n d i c a t e 95% c o n f i d e n c e l i m i t s
of mean.
DAILY TRAVEL DISTANCE
km/day
o
o J^"
05
z
o
:>
0)
I
> o
m
03
0>
m
>
m
>
00
c
z
o
>
z
o
m
01
LZ
cn
CO
I
05
•
-^i
1
oo
38
0.5 h a r e s / h a , mean DTD was 3.3 km ( 9 5 % c . i .
hare d e n s i t y
declined
DTD i n c r e a s e d
is
a
still
sharply
t o 5.3 km ( 9 5 % c . i .
significantly
hares/ha
f u r t h e r t o 0.2
larger
distance
foraging
effort
with
travel distance
(Figure
hares/ha
As
mean
lynx
3.9 t o 7.2 km).
This
than that
travlled
a t 1.0
( t - t e s t P< 0 . 0 5 ) .
A d d i t i o n a l evidence supporting
daily
2.8 t o 3.7 km).
8).
declining
recorded at
the idea that
lynx
increase
h a r e a b u n d a n c e i s t h e maximum
high
and
low
T h e s e d a t a show t h e same g e n e r a l
hare
density
t r e n d a s do mean
DTD.
A t 14.7 h a r e s / h a t h e maximum DTD I r e c o r d e d was 5.8
This
stayed
relatively
r e c o r d e d DTD was s t i l l
constant
6.3 km.
km.
t o 1.0 h a r e s / h a when maximum
As h a r e
densities
declined
0.5
and
t h e n t o 0.2 h a r e s / h a maximum DTD i n c r e a s e d
14.6
km r e s p e c t i v e l y , s h o w i n g a d e c r e a s e a t e x t r e m e l y
to
t o 17.5 a n d
low
hare
density.
Effect
o f Snowshoe H a r e P i s t r i b u t i o n
While
trying
t o capture lynx
on L y n x F o r a g i n g
f o r radio-tagging,
d a t a t o show how t h e y were c o n c e n t r a t i n g
i n areas of
Patterns
I
obtained
high
prey
density.
Between
declined
declined
1
and
May 10 1982, h a r e d e n s i t y
f r o m 14.7 t o 8.4 h a r e s / h a w h i l e
from
period,
3 lynx
nights
within
and
April
2.6
to
(Joy,
a
0.4
hares/ha
hare d e n s i t y
(Figure
t h e c a p t u r e of another lynx
of g r i d A (Table
(Charley)
on g r i d
2 ) . During
S c r u f f a n d S i d ) were c a p t u r e d
1 km r a d i u s
on g r i d A
B
this
i n 234
trap-
1 ) . From
tracks
i n the
same
area
on
39
Figure
8.
Maximum o b s e r v e d s t r a i g h t - l i n e t r a v e l d i s t a n c e
a l l l y n x i n e a c h 3 month p e r i o d f o r w h i c h home r a n g e s
were c a l c u l a t e d .
MAXIMUM OBSERVED
DAILY TRAVEL DISTANCE
KM
oi
o
01
ro
o
41
May . 2 5 ,
the
i t i s believed
that
a r e a a t t h e same t i m e .
four
the
lynx
r e s u l t e d i n no
Two h u n d r e d a n d f o r t y
Track
and
transects
densites
had
concentrated
hare
abundance
foraging
(Table
these
grid
hare d e n s i t y
captures.
b o t h g r i d s A and B i n t h e s p r i n g
o f 1982,
indicated that
efforts
5).
In
lynx
after
hare
sought out and
i n areas of r e l a t i v e l y
April
1982 when h a r e
t r a c k s c r o s s i n g a 600 m t r a n s e c t
A t t h e same t i m e ,
when h a r e d e n s i t y
1.6).
Thus,
lynx
used
s i g n i f i c a n t l y more ( G a d j .
was 0.8
the area of higher
test
they
were
depleted.
As h a r e d e n s i t y
f r o m 14.7 t o 2.2 h a r e s / h a , 3 o f t h e 4 l y n x
the
area dispersed.
declining
In
to
from
Hare d e n s i t y
sets
(95% c . i .
of
-0.1
hare abundance
hare
1982 when h a r e d e n s i t y
abundance
on g r i d A d e c l i n e d
I had r a d i o - t a g g e d
i n the surrounding
1.9 t o 1.4 h a r e s / h a d u r i n g
November
(95% c . i .
P= 0 . 0 0 5 ) .
Lynx abandoned t h e a r e a s of r e l a t i v e l y h i g h
when
of
on g r i d B was
f r o m 2.7 t o 1.2 h a r e s / h a , t h e mean number o f
l y n x t r a c k s c r o s s i n g e a c h 600 m t r a n s e c t
to
was 5.0
high
density
sets of lynx
declining
B
on t h e g r i d h a d
14.7 t o 9.5 h a r e s / h a on g r i d A, t h e mean number
t o 9.3).
in
i n t h e area of g r i d A
dropped from
0.7
2
captures.
the e a r l y winter
declined, also
their
on
1.8 h a r e s / h a , r e s u l t e d i n no
through
through g r i d A during
of
o f 1 l y n x p e r 7.3 km
s i x trap-nights
i n O c t o b e r a n d November 1982, a f t e r
to approximately
utilizing
Subsequent r a d i o - t r a c k i n g
An e q u a l number o f t r a p - n i g h t s
t h e same p e r i o d
declined
l y n x were a l s o
i n d i c a t e d a minimum d e n s i t y
a r e a o f g r i d A.
during
two o t h e r
this
areas
in
was
period.
on g r i d A had d e c l i n e d
1.8 h a r e s / h a , t h e mean number o f s e t s o f l y n x
tracks per
600
42
T a b l e 5.
E f f e c t o f r e l a t i v e snowshoe h a r e a b u n d a n c e on l y n x
foraging patterns.
*' and *
indicate a significant
d i f f e r e n c e (Gadj.
T e s t P= 0 . 0 0 5 ) .
TN i n d i c a t e s t h e
t o t a l number of t r a p - n i g h t s o f e f f o r t .
2
43
Grid
Hare d e n s i t y
(hares/Ha)
Number o f l y n x
c a u g h t / 1 00
trap-nights
Sets of lynx
t r a c k s / 6 0 0 meter
transect
(mean & 9 5 % c.i.)
A
April/82
14.7
B
April/82
2.6
0.0
(234 TN)
0.8
(-0.1
*i
A
Nov./82
1 .8
0.0
(246 TN)
1.2
( 0 . 0 t o 2.3)
1 .3 (234 TN)
5.0
( 0 . 7 t o 9.3)
*
1
* 2
* 2
t o 1.6
44
m
transect
declined
significant
reduction
decline
A p r i l and
(Gadj.
in u t i l i z a t i o n
d i f f e r e n c e i n the
second area
old Alaska
1983
of
test,P=
intensity
t o 2.3).
is a
following
the
0.005).
densities
Highway.
Five
t h a t n o t e d on
lynx
15 km
T h e r e was
no
of g r i d B i n
were
similar
n o t e d between. J u l y
of g r i d
19.8
As
km .
2
of
different.
The
second
was
not
d e g r e e o f home r a n g e o v e r l a p
generally
Unfortunately,
concentration
higher
I do
not
than
noted
have d a t a
in
elsewhere
on
on
the
area
of
99
i s lower
p r e v i o u s l y mentioned, the
this
area
along
This density
for individuals residing
second
A
resided within a total
1 l y n x per
g r i d A.
SE
was
of home r a n g e o v e r l a p
was
This
of l y n x use
lynx concentration
approximately
f o r a d e n s i t y of
than
0.0
of t h e a r e a
g r i d A i n November when h a r e
September
2
(95% c . i .
t e s t P>0.05).
A
km
1.1
i n hare abundance (Gadj.
significant
and
to
degree
grid
A
and
significantly
these
in
2
the
hare d i s t r i b u t i o n
areas
study.
in
this
area.
L y n x P i s p e r s a l and
M o r t a l i t y during
a Pecline
i n Snowshoe H a r e
Abundance
Puring
survived
the
study
only
f o r 1 y e a r o r more and
3
of
the
of
of
1984
7 lynx.
(Table
One
radio-tagged
remained w i t h i n the
D i s p e r s a l o r human r e l a t e d m o r t a l i t y were
loss
11
study
responsible
lynx
area.
for
l y n x d i e d of n a t u r a l c a u s e s i n the
the
spring
2).
Between A p r i l and
November 1982,
I radio-tagged
7 lynx.
By
45
April,
1983, o n l y 2 were s t i l l
study
area.
and
residing
being
trappers
9).
(Figure
g r i d A between A p r i l
residency
trapped
and
killed
A l l 3 of these
4 and May
times
months r e s p e c t i v e l y .
the
These
professional
individuals
o f 35 d a y s ,
One o f t h e f e m a l e s
period
significantly
density
on
the
and
grid
mid-December
40 d a y s a n d 7
( J o y ) was
at
was
declining
i n mid-December
approximately
her
home
She
dispersed
km o f t h e a r e a where C h a r l e y was
Joy,
months
before
i n NE A l a s k a .
from
Joy
being,
Charley
the
area
was
in
near
5 km SE o f
study
i n mid-November
killed
Pelly
area
in
within
50
Crossing,
C h a r l e y a n d S c r u f f h a d minimum d i s p e r s a l r a t e s o f
1.7 a n d 8.3 km/day r e s p e c t i v e l y
travel.
hare
(Figure 2).
range t o a p p r o x i m a t e l y
was t r a p p e d a n d k i l l e d
line
2
1982.
moved
by
8
but
250 km N o f t h e s t u d y
October.
covered
rapidly
next
1982 ' a n d
3.8,
least
1 year o l d .
surrounding areas
grid A in July
Yukon.
had
J o y and C h a r l e y d i s p e r s e d , g r i d A had
700 km i n t h e
killed
t r a p p e d and k i l l e d
Scruff
when
h i g h e r d e n s i t i e s than
t r a v e l l e d at least
captured
the
l y n x were r a d i o - t a g g e d on
25 1982.
i n the area
by
y e a r s o l d and t h e o t h e r 2 i n d i v i d u a l s were a t l e a s t
During
within
Three of t h e 7 ( J o y , C h a r l e y and S c r u f f ) d i s p e r s e d
250-700 km b e f o r e
minimum
alive
these
lynx i n the time
A l l dispersals
to
taken,
travel
the
i f I assume
distances
straight-
from t h e s t u d y a r e a o c c u r r e d d u r i n g
t h e s n o w - f r e e p e r i o d f r o m May t o O c t o b e r .
Two a d d i t i o n a l
killed
the
within
winter
l y n x ( S i d and S c o t t i e ) were a l s o t r a p p e d and
10 km o f t h e i r
of
1982-83.
original
A l l 5
radio-tagging site
during
l y n x were t r a p p e d w i t h i n
2.5
46
Figure
9.
Map o f l o n g d i s t a n c e d i s p e r s a l s u n d e r t a k e n by
lynx.
Star indicates i n i t i a l radio-tagging s i t e f o r
all individuals.
X,,^and X j i n d i c a t e s i t e s where
C h a r l i e and S c r u f f a n d J o y r e s p e c t i v e l y were t r a p p e d and
killed.
See T a b l e 2 a n d t e x t f o r d a t e o f i n i t i a l
r a d i o - t a g g i n g , d a t e k i l l e d and d i s p e r s a l r a t e s .
48
months o f t h e s t a r t o f t r a p p i n g s e a s o n .
my
radio-
tagged
p o p u l a t i o n a n d 100% o f t h e a n i m a l s
t h e game s a n c t u a r y .
in
the
present
Kluane
The 2 l y n x
Game
Sanctuary
late
1983,
4
within
the
d i s t a n c e d i s p e r s a l , of the
remained
1982 were
still
game
additional
sanctuary.
type
observed
lynx
I observed
the
were
no l o n g
preceding
year
r a p i d d e c l i n e i n snowshoe h a r e a b u n d a n c e .
During
were t r a p p e d
the
w i n t e r o f 1983-84, 2 o f my 6 r a d i o - t a g g e d
a n d k i l l e d w i t h i n 10 km o f
This represents
lynx
Haines
their
3 3 % o f my r a d i o - t a g g e d
o f t h e l y n x known t o h a v e t r a v e l l e d
One
fall
left
the following spring.
radio-tagged
site.
in
71% of
that
(Jean and C a r l o s ) t h a t
Between J u l y a n d S e p t e m b e r
during
This represents
initial
lynx
capture
p o p u l a t i o n a n d 50%
o u t s i d e t h e game
sanctuary.
(Rene) s t a r v e d a n d was f o u n d d e a d i n J u n e 1984 n o r t h o f
Junction,
35
c a r c a s s was e x t r e m e l y
km e a s t
of h e r i n i t i a l
emaciated,
and
I
capture
believe
site.
she
The
starved
during the winter.
Trapping
in
this
to
travel
was r e s p o n s i b l e f o r 7 o f 8 d e a t h s o f l y n x
study.
Furthermore, only 2 of the 9 i n d i v i d u a l s
o u t s i d e t h e game s a n c t u a r y
were n o t t r a p p e d .
observed
during the trapping
known
season
49
DISCUSSION
The
results
behaviorally
following
to
of
this
declining
sections
I
indicate- that
snowshoe
will
responses i n the lynx's
energetic
study
hare
discuss
efforts
lynx
abundance.
respond
In the
the e f f e c t i v e n e s s of these
to
continue
to
fulfill i t s
needs as h a r e abundance d e c l i n e s .
L y n x Home Range S i z e
Mean
home
f o l d concurrent
14.7
to
size
f o r lynx
with a decline
about
completely
range
range
0.2
hares/ha.
in this
i n snowshoe h a r e
This
increase
contrast
snowshoe
unclear
the
hare
to
t h i s study,
3
from
was s u f f i c i e n t t o
Brand e t a l .
density.
technique
lynxes
reason
used t o assess
"(1) errors
by
restricted
and
home
tracks
technique
are
from
to winter,
sexes of the study
to
(3) t h e area
animals
either
a f u n c t i o n of
day,
The work o f
snow
identifying
(2)
of search
often
cannot
or
differences
h a v e been p o i n t e d
in
lynx
difference i s
home r a n g e s i z e .
possible
day
( 1 9 7 6 ) f o u n d no
for this
(1976) was c o n d u c t e d u s i n g w i n t e r
l i m i t a t i o n s of t h i s
(1980):
The
b u t may be a t l e a s t p a r t i a l l y
Brand e t a l .
the
abundance
o v e r s h a d o w any e f f e c t o f s e x , a g e , o r s e a s o n on
r e l a t i o n s h i p between l y n x home r a n g e s i z e
The
increased
size.
In
in
study
tracking.
o u t by Mech
individual
observations
are
i s l i m i t e d , and (4)
be
determined".
50
Points
1 a n d 3 may be r e s p o n s i b l e
home
range
that
the
f o r t h e l a c k o f an i n c r e a s e i n
s i z e f o u n d by B r a n d e t a l .
expansion
unmonitored
areas
of
individual
went
lynx
undetected.
i t s home r a n g e i n t o t h e r a n g e o f
(1976).
I t i s possible
home
ranges
I f an i n d i v i d u a l
another,
this
into
expanded
expansion
may
have gone u n d e t e c t e d b e c a u s e o f m i s i d e n t i f i c a t i o n o f t h e t r a c k s .
Brand e t a l .
sampling
probably
of
a l s o s t a t e d t h a t home r a n g e s i z e was a f u n c t i o n o f
intensity,
have c o n t i n u e d
home
ranges
to increase
variation
for lynx
technical
differences
f a c t o r i s food
i n previous
Brand e t a l .
their
study
additional
high
would
kilometers
p e r i o d of
reported
home
rapid
lynx
that the
Home r a n g e s i z e s
reported
20.7 km
limited
2
ranges
of
home
Carbyn
between
in
hare
and
(1963b)
by
during
span f r o m t h e s m a l l e s t
2
(1983)
during a
Mech
(1980),
and suggested
f o rthe large
H i s estimates
a r e based
snow t r a c k i n g w h i c h may n o t h a v e been
Rene
l y n x home
Patriquin
abundance.
2
i n areas
that
home
f o u n d l y n x home r a n g e s b e t w e e n 15.5
t o d e l i n e a t e t h e e n t i r e home r a n g e s .
covered
working
138 a n d 221 km
r a n g e s o f 51 t o 243 km
a t low hare d e n s i t i e s .
winter
magnitude.
snowshoe h a r e a b u n d a n c e , r e p o r t e d
increase
Saunders
of
(1983),
p r e y a b u n d a n c e may h a v e been r e s p o n s i b l e
ranges.
some o f t h e
f o rlynx, I feel
et a l .
2
lynx
explain
s t u d i e s s p a n o v e r an o r d e r
(1976) and P a r k e r
relatively
found
may
abundance.
r a n g e s b e t w e e n 7.9 a n d 49.5 k m .
and
with
i n home r a n g e s i z e s r e p o r t e d
over-riding
low
in
snow-tracking.
Although
of
and
If
I
include
on
sufficient
the
area
t h e summer o f 1983, my 9 0 % home r a n g e s
to the largest previously
reported.
51
The
size
concept of i n c r e a s i n g
with declining
h a s been d i s c u s s e d
1978,
Harestad
among o t h e r s ) .
has
come
1976,
or
food abundance i s i n t u i t i v e l y
i n theoretical
and
Bunnell
Field
home
Simon
t e r m s by s e v e r a l a u t h o r s
1979, H i x o n
( AHaber
mammals
Northcote
1974).
obviously
not
effort,
individuals
(see D i l l ,
home
range
Although
increase
1976) a n d f i s h
increasing
foraging
home
(Slaney and
range
size
resources
r a n g e w o u l d n o t be d e p l e t e d a s r a p i d l y .
evident
A
i n May 1982 h a d a mean home r a n g e s i z e o f 13.2 k m .
f r o m my d a t a .
uniform hare d e n s i t y
contain
throughout t h e a r e a each
about
19,400 h a r e s .
t h i s home r a n g e a n d r e q u i r e d
this
with
hare
p o p u l a t i o n would
the 4 lynx
density
would
them
l y n x home r a n g e s a t t h i s
immediate
decline
lynx
needs.
Assuming
i n the hare p o p u l a t i o n
25.1
km
2
At
the
of
58.8 y e a r s .
time
were
2
27
years.
range
106 y e a r s .
29.2
km
Even
this
2
hare
I t t h e r e f o r e seems t h a t
well
in
i t seems
excess
of
unlikely
their
that
the
i n t h i s a r e a c a n be a t t r i b u t e d t o
hares/ha
when
lynx
home
s t a n d i n g c r o p of hares w i t h i n
range, a g a i n assuming e x c l u s i v e use, would
lynx
home
f o r maintenance,
the lynx over
area
Furthermore,
predation alone.
averaged
last
grid
I f a lynx had e x c l u s i v e use
0.5 h a r e s / d a y
sharing a t o t a l
last
lynx
the
This
The 4 l y n x u s i n g t h e a r e a a r o u n d
2
would
would
within
is
of
1968 f o r
success i n terms of c a t c h per
i t w o u l d mean t h a t t h e f o o d
home
size
(Krekorian
1978 a n d S c h o e n e r ,
et a l .
(Dill
1980, a n d McNab 1963
evidence f o r increasing
1975), b i r d s
range
r e a s o n a b l e and
from such wide r a n g i n g systems as r e p t l i e s
reviews),
unit
feeding t e r r i t o r y
last
A t - 0.5 h a r e s / h a t h e e x i s t i n g
ranges
i t s home
an
individual
hare
population
52
w i t h i n t h e a v e r a g e l y n x home r a n g e o f 39.2 km
10.7
years.
still
f u r t h e r and
within
Overlapping
the
t h e 99.0 km
home r a n g e s w o u l d d e c r e a s e
hare
shared
2
population
them o n l y a b o u t 5.4 y e a r s .
that
increase
in
d e c l i n i n g hare
abundance
constant
hare
size
lynx
home
was
survive
that
lynx
totally
deplete
are
their
sufficiently
home
range.
Prey
have t o e x p e n d more e f f o r t
response
not
home r a n g e .
a
These
that
predators
lynx
It
to
directly
to
prey
As p r e y a b u n d a n c e d e c l i n e s t h e
of
i n e q u i v a l e n t prey
to
find
and
capture
a l y n x ' s home r a n g e s i z e i n
assumes
hares
w i t h i n t h e l y n x ' s home r a n g e .
and
that
other
no
availability
also
relatively
h i g h prey
If prey
were
seemed
I noted
also
to
i n this
important
concentrate
i s not uniform
e x p a n d i n g i t s home r a n g e ,
home r a n g e .
lynx.
It
study
that
p r e d a t o r s on
i n areas
of
abundance.
distribution
the chance of having
f o r the
o t h e r p r e d a t o r s a r e h a r v e s t i n g snowshoe
mammals
snowshoe h a r e s , a n d a l s o
by
maintain
t o a h a l v i n g o f snowshoe h a r e a b u n d a n c e w o u l d t h e r e f o r e
result
raptors
to
abundance w i t h i n a
extrapolated
doubling
i n response t o
efficient
predator w i l l
A
show
w i t h i n i t s home r a n g e .
f o r the predator.
item.
time
recruitment)
t h e amount o f t i m e
availability
prey
size
sufficient
existing
p r e d a t o r s home r a n g e c a n n o t be
each
this
calculations
population within their
on t h e h a r e s
assumes
These
range
not
estimates obviously over-estimate
could
(without
about
by 5 r e s i d e n t s i n t h e summer o f 1983
would l a s t
the
would l a s t
2
w i t h i n the environment,
the individual
would a l s o i n c r e a s e
r e l a t i v e l y good p a t c h e s
of prey w i t h i n i t s
T h i s w o u l d be e s p e c i a l l y
important
t o a lynx during
53
a
snowshoe
hare
decline
concentrated within
will
be
Three
hare
remaining
i n the l a t e r
hares
(1980).
are
This
s e c t i o n on p a t c h
by l y n x .
l y n x a b a n d o n e d t h e i r home r a n g e s a n d
densities
below about
0.5 h a r e s / h a .
h a v e been r e p o r t e d f o r o t h e r f e l i d s .
found
few
r e f u g i a a s s u g g e s t e d by W o l f f
d i s c u s s e d i n more d e t a i l
utilization
at
i f the
Hanby
t h a t t h e number o f n o m a d i c f e m a l e
became
nomadic
Similar patterns
and
Bygott
(1979)
l i o n s wandering
through
t h e s u b o p t i m a l h a b i t a t o f t h e S e r e n g e t i P l a i n s d e c l i n e d a n d some
o f t h e s e p r e v i o u s l y nomadic f e m a l e s became
abundance
defended
increased.
territories
Bailey
during
resident
prey
abundance
periods
of
prey
well
f o rlynx.
He s u g g e s t e d
not
be
seek
out patches of r e l a t i v e l y
have
good
fulfill
their
out
widely
0.5 h a r e s / h a , l y n x
may
e n e r g e t i c r e q u i r e m e n t s a n d must
h i g h prey abundance.
i n f o r m a t i o n on t h e s p a t i a l a n d t e m p o r a l
snowshoe h a r e s
that
These arguments h o l d e q u a l l y
At d e n s i t i e s below about
to
also
i s u n p r e d i c t a b l e , o r v e r y l o w , i t w o u l d be
c o n c e n t r a t i o n s of prey.
able
that
abundance
a d a p t i v e f o r b o b c a t s t o become t r a n s i e n t a n d s e a r c h
seperated
prey
(1981) r e p o r t e d t h a t b o b c a t s
became n o m a d i c a f t e r p r e y a b u n d a n c e d e c l i n e d .
if
when
i n my a r e a b u t i f t h e r e f u g i a a r e
I
do n o t
distribution
widely
spaced
i t may be n e c e s s a r y f o r l y n x t o wander g r e a t d i s t a n c e s i n s e a r c h
of
and
them.
Mean home r a n g e
o v e r l a p f o r l y n x exceeded
10.5% b o t h
between
throughout
Further, absolute
sexes
this
snowshoe h a r e d e n s i t y h a d no e f f e c t
overlap
between
lynx.
The
study.
on t h e d e g r e e
degree
of
o f home
home r a n g e
within
range
overlap at
54
extreme
h i g h and low hare
significantly
densities
this
(1968)
proportional
to
individuals.
suggested that t e r r i t o r i a l i t y
the
Bailey
degree
of
(1974)
found
b o b c a t s o v e r l a p p e d 0.1 a n d 2.0
with
females
home
range
the
percent
respectively.
The
evidence
that
exclusiveness
of
Nellis
(1972)
et a l .
time and space.
overlap
lynx
home
males,
h i g h degree
o f home
in
this
is
during
abundance.
trend
in
the
relative
ranges w i t h i n and between s e x e s .
r e p o r t e d t h a t l y n x t e n d t o be s e p a r a t e d i n
Brand e t a l .
space, but p r o b a b l y does
mechanism".
study
at least
(1976)
reiterated
this
" avoidance behavior appears t o separate lynx
limiting
between
with
lynx a r e not t e r r i t o r i a l
P r e v i o u s s t u d i e s show no c o n s i s t e n t
and
not
i s inversely
f o r male
p e r i o d o f d e c l i n e a n d l o w snowshoe h a r e
that
were
home r a n g e s o f t e r r i t o r i a l
range o v e r l a p w i t h i n and between a l l sexes
strong
study
different.
Schoener
females
in
Berrie
not
act
(1974)
locally
found t h a t
stating
i n both time
as
a
density-
female lynx
were
" l e s s t o l e r a n t o f e a c h o t h e r t h a n were m a l e s " .
In h i s study the
home r a n g e s
other
neighbouring
Mech ( 1 9 8 0 )
those
of
males
reported that
of males d i d not.
(1983)
with
each
and
with
f e m a l e s w h i l e f e m a l e home r a n g e s d i d n o t o v e r l a p .
also overlapped l i t t l e
reported
f e m a l e home
ranges
overlapped
while
I n h i s s t u d y , home r a n g e s o f m a l e
w i t h those of females.
extensive
a d u l t male and female
two
overlapped
overlap
i n h i sstudy.
in
Parker
lynx
et a l .
t h e home r a n g e s o f t h e
The home
ranges
a d u l t s d i d not o v e r l a p w i t h that of a j u v e n i l e
he p r e s u m e d t o t o be t h e o f f s p r i n g o f h i s a d u l t
of
female
female.
these
which
Carbyn
55
and
Patriquin
(1983) f o u n d t h e home r a n g e s o f two f e m a l e s
k i t t e n s overlapped
b u t i t was u n c e r t a i n w h e t h e r t h e
of t h e m a l e i n t h e i r
The
was
lynx
i spuzzling.
population
not monitored.
overlapped
cases.
overlapped
w i t h i n the study
a
function
distribution
of
A
of
environmental v a r i a b l e s .
degrees
of
tolerated.
might
home
areas of these
range
of
reported
which
second
I f any b e h a v i o r a l
populations,
factors
such
i ti seasily
as
utilization
studies
within
these
spacing
over-ridden
would
i s that
function
conditions
and
of
the
subtle
different
between s e x e s i s
enironmental
factors
from a review
of past
mechanism
exists
by p r o x i m a t e
snowshoe h a r e d i s t r i b u t i o n
by l y n x ) .
some
animals i n the population
various
what
in
i n the l i t e r a t u r e
is a
overlap
lynx
possibility
lynx
Under
No i n d i c a t i o n o f
monitored
be o r how t h e y m i g h t a c t i s e v i d e n t
studies.
patch
those
of o v e r l a p
h a p p e n e d t o be m o n i t o r e d .
spatial
i s that the
The home r a n g e s o f u n m o n i t o r e d l y n x may have
The p a t t e r n s
be
i n t h e d e g r e e o f l y n x home
One p o s s i b l e e x p l a n a t i o n
extensively with
therefore
range
with that of the females.
l a c k of a c o n s i s t e n t p a t t e r n
range o v e r l a p
total
study
home
with
in
lynx
environmental
(seed i s c u s s i o n of
56
Effect
of Snowshoe H a r e Abundance on Lynx F o r a g i n g
Lynx
travel
i n t h i s study
distance
f r o m 2.7
km/day
at
(1968),
Brand et a l .
(1983)
a l l f o u n d no
and
low
hare
the d i s t a n c e
N e l l i s and
winter
daily
daily
travel
that
lynx
km/day a t
density.
(1976),
high
In
Keith
a
hare
(1981) and
( 1 9 6 8 ) and
per
distance
daily
and
of
lynx
negative
hunting
travel
through
(1968),
distance
was
kills/km.
hunting
and
et
al.
success,
et a l .
and
concurred
( 1 9 7 6 ) and
therefore
snow c o n d i t i o n s and
(1981)
daily
attempt,
with N e l l i s
daily
distance,
did
not
increase
t h e i r DTD
signi-f-icantly with
h a r e a b u n d a n c e i n summer, when
snow
affecting
Further,
distance
kills
hunting
i s an
per
day
success.
inverse
and
conditions
if
f u n c t i o n of h u n t i n g
(Brand et a l .
1976,
is
a
declining
not
daily
success i n
Parker
that
hares/ha
could
(1)
of
skills.
I f o u n d , h o w e v e r , t h a t a t h a r e d e n s i t i e s a b o v e 1.0
lynx
and
travel
(1981) s u g g e s t
hunting
8
found,
success i n terms
travel
individual
found
He
per
that
Parker
lynx
at about
winter.
kills
(1976)
markedly
between
remained constant
He
that
Brand et a l .
Parker
i n t e r m s of
winter.
Brand
al.
(1976) f o u n d
correlation
p r i m a r i l y a f u n c t i o n of h u n t i n g
Brand
f u n c t i o n of
the
Keith
et
fluctuated
success.
distance
success,
5.3
day.
i n d e p e n d e n t of h a r e a b u n d a n c e .
however, t h a t h u n t i n g
Keith
Parker
Brand et a l .
(DTD)
significant
to
b e t w e e n snowshoe h a r e a b u n d a n c e
km/day as h a r e a b u n d a n c e d e c l i n e d t h r o u g h one
increased
density
daily
c o n t r a s t , N e l l i s and
Parker
correlation
travel distances
found
t h e i r mean s t r a i g h t - l i n e
that lynx t r a v e l l e d
from year to y e a r ,
(1976)
increased
Effort
be
travel
terms
1 9 8 1 ) , (2)
of
there
57
is
no
r e l a t i o n s h i p between k i l l s
(Brand
et
al.
1 9 7 6 ) , and
per
travel
fulfill
studies
increased
1.0
hares/ha.
and
Keith
nights
(1968)
only
c o u l d be
dramatic
instances
where l y n x
et a l .
a l l
Parker
increase
My
in
effort
to
lynx
et a l .
higher.^
their
distances,
In
any
foraging effort
be
it
data
that
was
event,
on
not
travelled
occurs
0.7
consecutive
I t may
total distance
r e s u l t s a b o v e 0.5
The
(1983),
or
"beds u s e d on
long
omitted.
showed
seasons.
to c o l l e c t
the
and
most
at very
low
hares/ha t h e r e f o r e are
in
agreement w i t h t h o s e of Brand e t a l .
( 1983) .
lynx
hare d e n s i t i e s below
established with c e r t a i n t y " .
were t h e r e f o r e
hare d e n s i t i e s .
general
1976),
hares/ha
at
f o r them t o e s t a b l i s h t h e
these data
0.7
snow-tracking
d a y s when l y n x t r a v e l l e d u n u s a l l y
possible
in
(1976) and
worked
They u s e d w i n t e r
reported
travelled
h a r e s / h a , however, lynx
in foraging effort
of both Brand et a l .
and
km
(Brand et a l .
were c o n d u c t e d a t h a r e d e n s i t i e s of
Nellis
per
density
requirements.
h a r e d e n s i t i e s of
a dramatic
hare
f u r t h e r as h a r e a b u n d a n c e d e c l i n e s i n an
their energetic
Below
and
(3) a t t e m p t e d k i l l s
d e c l i n e with d e c l i n i n g hare density
should
attempt
( 1 9 7 6 ) and
Parker
58
I c a l c u l a t e d expected t o t a l d a i l y
at d i f f e r e n t
hare d e n s i t i e s u s i n g
the
travel distances
^energy
lynx
equation:
maintenance
expected
for
level
requirement.
daily
travel
Y
di
regression
stance
i n t e r c e p t of
for
data
from
parameter
line
per
of
attack
regression
contrast
found that
lynx
t h i s higher
doubling
rate
al.
(1976)
I
of the
at
following
line =
hares/day
17.5
( p r o p o r t i o n of
to
successful attacks)
Brand et a l . ( l 9 7 6 ) ,
an
average of
r a t e i n the
1 hare per
above e q u a t i o n
expected d a i l y
travel
average i n d i v i d u a l
would a g a i n
Parker
tend
.23
et a l .
(1983)
Substituting
would
result
distances.
Parker
hunting
to
day.
=
in
(1981)
s u c c e s s r a t e of
increase
the
a
expected
17%.
daily
distances.
Using
daily
an
lower value
travel
set
l i n e = 0.075
kill
kill
also reported
This
success
values;
success rate
In
X
_
et
i n t e r c e p t of r e g r e s s i o n
slope
density
X
m a i n t e n a n c e l e v e l e n e r g y r e q u i r e m e n t = 0.5
Y
attack
hare
line
km
Brand
of
regression
attempted
kills
Using
slope
a range of h a r e abundances
travel
distance
curve
shown a s
I
derived
the
line A in Figure
expected
10.
From
59
Figure
10.
O b s e r v e d and e x p e c t e d t o t a l d a i l y t r a v e l
d i s t a n c e s f o r l y n x v e r s u s snowshoe h a r e a b u n d a n c e .
d e r i v a t i o n o f l i n e s A, B and C s e e t e x t .
For
EXPECTED TOTAL DAILY
T R A V E L DISTANCE
(KM)
61
N e l l i s and K e i t h
daily
travel
(1968) and S a u n d e r s (1963b) I c a l c u l a t e d
distance
r a t i o s o f 3.0
and
straight-line
1.9
to
straight-line daily
respectively.
daily
values, to estimate t o t a l daily
plotted
in Figure
travel distance
I therefore
t r a v e l d i s t a n c e s by 2.5,
multiplied
t h e mean o f
travel distance.
my
to
mimic
my
10.
data
accurately.
under-estimated
abundances and
at
Daily
very
above
(1976).
Although
line
unreasonable.
suggests
the
correlation
are
low
slope parameters
coefficient
hare
Y
intercept
considerably
to attempt
reasonable the r e g r e s s i o n
or i n t e r s e c t the x - a x i s near the
lines
can
in
(Fig.
11); a s t r a i g h t
line
their
biologically
higher
than
zero
to k i l l
hares
long
to k i l l .
Clearly
origin.
Two
(Holling
the
their
data
to
a
Both r e s u l t
in a
s l o p e f o r t h e r e g r e s s i o n l i n e a t low h a r e d e n s i t i e s .
The
type I I f u n c t i o n a l
response curve
s l o p e a t h i g h hare
densities.
also
1959).
be
possible
r e g r e s s i o n or a c u r v e s i m i l a r
response
to
l i n e must r u n t h r o u g h
drawn t h r o u g h t h e o r i g i n t o i n t e r s e c t
functional
used
for
2
origin
II
very
i s good,(r =0.91) these values are
A
be
distances
and
that lynx are c o n t i n u i n g to attempt
biologically
larger
similar
a r e d e r i v e d from F i g u r e 2 of Brand e t a l .
t h e r e a r e no h a r e s l e f t
type
is
over-estimated at intermediate d e n s i t i e s .
equation
regression
travel
high
E s t i m a t e s f o r t h e Y i n t e r c e p t and
after
also
o b s e r v e d v a l u e s , t h e i n f l e c t i o n p o i n t i s n o t s h a r p enough
therefore
the
my
these
These a r e
A l t h o u g h the curve through the expected v a l u e s
to
total
results
in
a
smaller
L i n e B o f F i g u r e 10 shows p r e d i c t e d v a l u e s f o r t h e
straight
62
Figure
11.
R e p r o d u c t i o n o f F i g u r e 2, B r a n d and K e i t h ( 1 9 7 9 ) ,
w i t h 2 a d d i t i o n a l r e g r e s s i o n l i n e s added.
Line A i s
t h e o r i g i n a l r e g r e s s i o n l i n e p r e s e n t e d by B r a n d and
K e i t h (1979).
L i n e s B and C a r e a l t e r n a t i v e , more
b i o l o g i c a l l y reasonable r e g r e s s i o n s p a s s i n g through the
origin.
See t e x t f o r e x p l a n a t i o n and j u s t i f i c a t i o n o f
l i n e B and C.
63
B
100
200
300
400
500
S N O W S H O E HARES/100 Ha
of HABITAT (1 DECEMBER)
64
line
regression
through
the o r i g i n
(line B Fig.
11) u s i n g t h e
above e q u a t i o n w i t h a Y i n t e r c e p t o f z e r o and a s l o p e of
The
resulting
r
v a l u e o f 0.11 f o r t h i s
2
t h a t o f 0.91 r e p o r t e d by B r a n d
more b i o l o g i c a l l y
The
inflection
too
high
a
p o i n t of the r e s u l t i n g
hare
e s t i m a t e s i t a t high hare
I therefore plotted
fit
on
log-log
at
the data
through
than
0.91 r e p o r t e d by B r a n d
this
line
value
i s again
the o r i g i n .
functional
from
data,
occurs
l i n e a l s o g r o s s l y over-
hare
densities
and
under-
from F i g u r e 2 of Brand
for this
line
et a l .
biologically
et a l .
(line
i s 0.87, o n l y
(1976).
reasonable
(Holling,
(Krebs
C,
slightly
Furthermore,
because i t goes
T h i s i s a l s o t h e g e n e r a l form o f
response
vertebrate predators
intercept
however,
( l i n e B, F i g .
t h e i r data t o the o r i g i n
lower
II
is
densities.
The
2
line
the observed
This
low
Fig.11).
through
It
than
s c a l e , t h e e q u i v a l e n t of c a l c u l a t i n g a best
h y p e r b o l i c curve
r
resembling
density.
estimates t r a v e l distance
(1976)
(1976)
i s f a rless
reasonable.
1 0 ) , a l t h o u g h more c l o s e l y
at
et a l .
line
0.13.
the
type
1959) t h a t i s common f o r many
1978).
Using
the
slope
t h i s t r a n s f o r m a t i o n we a g a i n c a l c u l a t e d
t r a v e l d i s t a n c e s w i t h t h e above e q u a t i o n .
and
Y
expected
These a r e p l o t t e d
as
l i n e C on f i g u r e 10.
Although
this
line
slightly
over-estimates d a i l y
d i s t a n c e a t low d e n s i t i e s and u n d e r - e s t i m a t e s
at
extremely
correct
data
high
hare
travel
that
the
distances
d e n s i t e s , the i n f l e c t i o n point i s the
f o r m a n d o c c u r s a t t h e r i g h t p o i n t t o m i m i c my
so
travel
f i t of t h i s l i n e
observed
i s s u r p r i s i n g l y good.
The
65
slight
may
over-estimation
be
due
not
be
to
meet
result
hare
able
of t r a v e l d i s t a n c e
t o p h y s i o l o g i c a l c o n s t r a i n t s on
to t r a v e l
their
f a r enough p e r
energetic
densities.
The
sample
requirements
evidence
first
data
of
t h e day.
no
et a l .
apparent
above
the
1.0
densities.
Parker
hares/ha,
lynx
be
they
1.0
of
to continue
to f u l f i l l
i n t u r n , would
lynx
at
low
continuing
their
al.
et
t o e x p l a i n why
foraging effort
be
to
found
increase
their
that
energetic
my
accord.
(1976)
and
there
is
to
d r a m a t i c a l l y at
is
the
at hare d e n s i t i e s
extrapolated
increases
the
al.
at
energetic
(1983)
in strong
Brand
cannot
h a r e / h a but
densities
demonstrates
(1976) are
Lynx f o r a g i n g e f f o r t
may
travel distance
after
et
Lynx
hare
to lynx
also
sufficient
in lynx
lynx.
This,
of
densities
t o t r a v e l a f t e r consuming
T h i s model
explanations
increase
d e n s i t i e s below
for
met.
(1983) may
due
environment
t h o s e of B r a n d e t a l .
Although
Parker
been
be
that lynx often continue
kill
and
have
the
a t low
under-estimation
the
hare
body c o n d i t i o n of
e x t r e m e l y h i g h h a r e d e n s i t i e s may
and
day
requirements.
i n the d e c l i n e i n general
travel
a t low
not
lower
hare
sufficient
requirements.
66
Effect
o f Snowshoe H a r e D i s t r i b u t i o n
If
prey
environment
are
not
i t will
concentrate
its
uniformly
always
on L y n x F o r a g i n g P a t t e r n s
distributed
be t o t h e a d v a n t a g e
foraging
efforts
h i g h p r e y abundance (Krebs 1978).
i n t h e p a t c h e s of
This w i l l
t h e s u r r o u n d i n g a r e a s i n c r e a s e s and
the
predator
to f u l f i l l
the
of a p r e d a t o r
become
i m p o r t a n t as the r e l a t i v e d i f f e r e n c e between
and
throughout
the
to
relatively
increasingly
good
patches
i t becomes d i f f i c u l t
for
i t s e n e r g e t i c requirements o u t s i d e the
good p a t c h e s .
I do n o t h a v e good d a t a on t h e p a t c h i n e s s o f snowshoe
distribution
Wolff
but
i f the system
is similiar
( 1 9 8 0 ) snowshoe h a r e d i s t r i b u t i o n
clumped.
period
Wolff
of
retreat
(1980) s u g g e s t e d
their
into
ten
year
patches
optimal
then
and
t h e s e good p a t c h e s .
In t h i s
indicating
efforts
i t would
trapping
hare
abundance.
different
snowshoe
habitat.
been
Second,
It
would
lynx ' density
was
track
lines
of
transects
lynx
out
evidence
foraging
First,
through
my
high
areas
of
i n d i c a t e d t h a t l y n x used a r e a s of
than
higher within
h i g h prey abundance than e l s e w h e r e
that
seem
h i g h e r i n an a r e a o f r e l a t i v e l y
hare abundance a l s o
low
hare p o p u l a t i o n s
seek o u t and c o n c e n t r a t e t h e i r
s u c c e s s was
very
be a d a p t i v e f o r l y n x t o s e e k
h i g h h a r e a b u n d a n c e more i n t e n s i v e l y
found
have
i n p a t c h e s o f h i g h snowshoe h a r e a b u n d a n c e .
lynx
Third,
should
study I found t h r e e independent
t h a t l y n x do
t o t h a t d e s c r i b e d by
t h a t d u r i n g t h e d e c l i n e and
cycle,
reasonable
utilize
that
of
hare
in
surrounding
t h e p a t c h of
the
study.
areas.
relatively
Further,
I
a b a n d o n e d t h e s e good p a t c h e s when t h e y became
67
depleted.
O t h e r s have a l s o found t h a t
lynx
tend
to
p a t c h e s of r e l a t i v e l y h i g h prey abundance.
state
t h a t one o f t h e t h r e e
concentrate
during
their
cyclic
Saunders
efforts
Koehler
tend
after
et a l .
that
increase
suggested, supports
degree
the
of
densities
distribution
density,
food
(1974),
that
lynx
abundance.
below
hare
cannot
0.5
out of
population
meet
their
hares/ha,
hare d e n s i t y has l i t t l e
of
lynx,
but
effect
relative
prey
o f d i s t r i b u t i o n ) may p l a y a l a r g e r o l e
of l y n x .
The h i g h
found between t h e 4 l y n x d u r i n g
Although
i n the area
as
this* idea.
aggregation
was a f u n c t i o n o f t h e i r
abundance.
lynx
spatial distribution
o f home r a n g e o v e r l a p
prey
hare
snowshoe
That
above, a b s o l u t e
(patchiness
determining
1982
Berrie
then
of l y n x t h r o u g h t h e low o f
the
phase.
previously
As d i s c u s s e d
at
of
needs
abundance
and
and t h a t t h e e x p a n s i o n o f t h e lynx p o p u l a t i o n
the
the
numbers
high
this.
i n an a r e a o f
(1971) a l s o n o t e
f o rthe survival
energetic
on
especially
f u r t h e r s u g g e s t e d t h a t r e f u g i a f o r snowshoe
these r e f u g i a followed
during
a p e r i o d of low hare
i n areas of r e l a t i v e l y
(1974)
cycle
lynx concentrated
(1979) a n d B e r g e r u d
h a r e were i m p o r t a n t
the
that
(1976)
He d i d n o t q u a n t i f y
t h e c a r r i o n became u n a v a i l a b l e .
to concentrate
Berrie
i n areas of hare a c t i v i t y ,
reported
abundant c a r r i o n d u r i n g
Brand e t a l .
in
methods u s e d by l y n x was t o
lows i n hare abundance.
(1963a)
dispersed
hunting
concentrate
sharing
I
a patch
do
degree
April-June
of r e l a t i v e l y
have
data
high
on
prey
o f l y n x home r a n g e o v e r l a p a t l o w
hare
i t i s p o s s i b l e that t h i s area
not
in
a l s o had r e l a t i v e l y
high
6B
prey
of
abundance.
relative
extensively
overlap
L y n x home r a n g e o v e r l a p may t h e n
prey
abundance.
i n areas
i n areas
Lynx
of r e l a t i v e l y
of
high
relatively
also explain the large variation
home
be a
ranges
prey
low prey
o v e r l a p than
elsewhere
may
density
density.
overlap
and not
This
i n d e g r e e o f home r a n g e
between l y n x a t i n t e r m e d i a t e hare d e n s i t i e s i n t h i s
d e n s i t y was a l s o h i g h e r
function
i n t h e two. a r e a s
of
might
overlap
study.
Lynx
home
range
high
i n the study.
Lynx P i s p e r s a l and M o r t a l i t y
P u r i n g t h e p e r i o d o f r a p i d d e c l i n e i n snowshoe h a r e numbers
(January
through
radio-tagged
trapped
by
Pecember
1982)
d i s p e r s e d between
professional
3
250
of
and
trappers.
t h e 7 l y n x t h a t I had
700
km
Other
d i s p e r s a l s by l y n x o f f r o m 103 t o a p p r o x i m a t e l y
reported
elsewhwhere
by
other
researchers
N e l l i s a n d Wetmore 1 9 6 9 , Mech 1977, P.
These
d i s p e r s a l s are normally
before
long
being
distance
800 km h a v e been
(Saunders
Brittel
pers.
1963b,
comm.).
a s s o c i a t e d w i t h t h e d e c l i n e phase
o f t h e snowshoe h a r e c y c l e a n d l y n x h a v e been r e p o r t e d t o i n v a d e
areas
w e l l south
Gunderson
of t h e i r
1978).
normal range
T h i s and other
( Adams 1963, Mech
1973,
s t u d i e s have shown t h a t a d u l t s
as w e l l a s j u v e n i l e s u n d e r t a k e s u c h l o n g movements.
The
t h r e e d i s p e r s e r s i n my s t u d y
line
travel distances similar
for
resident
once t h e s e
lynx
animals
h a d minimum d a i l y
t o or l a r g e r than
d u r i n g t h e same p e r i o d .
abandoned t h e i r
home
those
straight
recorded
This suggests
ranges
they
that
d i d not
69
resettle
It
i n other
is
areas.
interesting
movements r e c o r d e d
decline
in
in
snowshoe
s t a b l i z e d a t a low
expanded
their
remained
within
represents
a
to
that
this
study
hare
numbers.
level,
home
note
(below
a l l the long
occurred
during
small
about
1.0
hares/ha.)
general
change
in
the
study
area.
response
s i z e i s not c l e a r .
c h a n g i n g and u n f a m i l a r
been s e e k i n g
the
past.
level
of
occurrence
I t m i g h t be t h a t
conditions similar
conditions.
the
lynx
a b u n d a n c e t h e y may
this
lynx to d i f f e r e n t
a
due
the long
response
T h e s e l y n x may
acclimated
to this
new
h a v e been l e s s i n c l i n e d
at
level
a
to
have
t o t h o s e t h e y had e x p e r i e n c e d
Once p r e y a b u n d a n c e became s t a b l e a g a i n
and
lynx
Whether
d i s t a n c e movements e x h i b i t e d by t h e s e l y n x were
rapidly
rapid
r a n g e d r a m a t i c a l l y , o r became n o m a d i c b u t
the
sample
the
A f t e r h a r e d e n s i t i e s had
environmental c o n d i t i o n s , or i s merely a chance
to
distance
in
lower
of
resource
towards such
dramatic
movements.
Man
was t h e s i n g l e most
in t h i s study.
known
to
m o r t a l i t y factor f o r lynx
P r o f e s s i o n a l t r a p p i n g was
of o b s e r v e d d e a t h s .
were
important
responsible
Only 2 of 9 r a d i o - t a g g e d
travel
outside
trapped;
most were t r a p p e d
trapping
season.
individuals
w i t h i n 2.5 m o n t h s o f t h e b e g i n n i n g
One o f t h e 2 a n i m a l s
mortality
found
65%
studies
rates i n lynx
of
a local
have
that
K l u a n e Game S a n c t u a r y were n o t
that
were
(Rene) d i e d o f n a t u r a l c a u s e s a n d p r e s u m a b l y
Other
f o r 7 of 8
also
reported
populations.
lynx population
trapped
starved.
high
Parker
was
not
of
et
trapped
human-related
a l .
i n the
(1983)
first
70
open s e a s o n a f t e r a one
3 of
year c l o s u r e .
5 lynx radio-tagged
five
months and
of h i s
i n 1972
a f o u r t h was
14 l y n x were k i l l e d
(1983)
report
that
were k i l l e d
killed
by
a l l three
were t r a p p e d
trapped
two
3
February
1965
of
the
of
9
three
adult
1965
and
believed
one
that
Brand
trapping
during
The
and
rates
of
(1979)
during
season
surprising
benign
makes
Their
them
mortality
(i.e.
from
occurs
May
to
time
of
year.
low
and
to data
Further,
was
fate
between
trapping
phase of
Non-
at 7 to
i n c l u d i n g an
assumption
the
start
of
I t would
be
during
studies.
38%
several
of
the
most
trapping
m o r t a l i t y r a t e s are
from the above t a g g i n g
the
phase.
contain
estimates
(1979)
apparently
annual
before
3
predated
is
decline
highest
h i s non-trapping
The
and
al.
et
November).
his
1964
Koehler
estimates
suspect,
(1972)
1 y e a r and
radio-tagged
early
was
dead w i t h i n
early increase
i f n a t u r a l m o r t a l i t y were
m o r t a l i t y are
compared
the
park.
one
tagged
estimated
the
the
and
r a t e s f o r a d u l t s were e s t i m a t e d
that a l l non-trapping
trapping
had
in Riding
tagging.
lynx
7
Patriquin
outside
f a t e of h i s second a n i m a l
e a r l y d e c l i n e phase.
that
1 was
within
N e l l i s et a l .
year of
eight
l y n x he
Keith
10%
Of
1968,
17-29% d u r i n g
mortality
assumptions
and
between August
l e a s t 1 year.
of two
by a m o u n t a i n l i o n .
h a r e c y c l e and
killed
tagged
w i t h i n one
February
a f t e r at
mortality
and
months l a t e r .
6 i s unknown.
were r e c a p t u r e d
unknown.
Carbyn
that
In t o t a l ,
lynx they radio-tagged
lynx
were t r a p p e d
remaining
August
humans
w i t h i n 4 months of r a d i o - t a g g i n g
y e a r s and
reported
by
w i t h i n a year.
humans.
M o u n t a i n N a t i o n a l P a r k were t r a p p e d
Two
Mech ( 1 9 8 0 ) r e p o r t e d
Combining
high
the
71
r e s u l t s of t h i s
estimates
with those previous
of Brand and K e i t h
important
55%
study
mortality
1979),
studies
man
(excluding the
i s the
factor i n lynx populations.
single
The d e a t h s o f
o f a l l l y n x t a g g e d i n t h e s e s t u d i e s were h u m a n - r e l a t e d .
those
animals
f o r which
responsible'for
mortality
in
95% o f
The
the m o r t a l i t y .
5.6% o f t a g g e d
behavioral
increase
combination
increased
distances
into
In
contrast,
lynx
vulnerability
home
range
size
to
w i t h more t r a p s .
trapping.
and
daily
bring
When p r e y a r e s c a r c e ,
high
Finally,
because lynx aggregate
lynx
area
hare
large proportion
by c o n c e n t r a t i n g
abundance.
If
his efforts
these
lowest.
This
may
s e n s i t i v e t o over-
i n areas of r e l a t i v e l y
lynx
r e s u l t i n lynx populations
snowshoe h a r e a b u n d a n c e .
trapper
of the lynx population
into the
harvesting during
might
i n areas of r e l a t i v e l y
f a c t o r s are important,
h a v e most e f f e c t when r e c r u i t m e n t
lynx
trapping
snowshoe h a r e a b u n d a n c e , i t w o u l d be p o s s i b l e f o r a
to trap a r e l a t i v e l y
the
A
travel
the
be more e a s i l y a t t r a c t e d t o t r a p b a i t s , t h u s i n c r e a s i n g
success.
f o r an
lynx.
w i t h d e c l i n i n g p r e y abundance s h o u l d
contact
natural
r e s p o n s e s o f l y n x t o d e c l i n i n g snowshoe h a r e
abundance s h o u l d
of
Of
t h e c a u s e o f d e a t h i s known, man i s
t h i s a n d t h e a b o v e s t u d i e s was r e s p o n s i b l e
annual l o s s of only
an
most
they
in
high
should
population
is
being e s p e c i a l l y
decline
and
low i n
72
Lynx S o c i a l
The
of
the
section,
social
s t r u c t u r e o f any
environment
I will
populations
and
Structure
in
which i t l i v e s
d i s c u s s the
the
mammalian s p e c i e s
social
(Fisler
is a
function
1969).
o r g a n i z a t i o n observed
In
this
in
lynx
e n v i r o n m e n t a l f a c t o r s t h a t have s e l e c t e d f o r
it.
L y n x , l i k e most f e l i d s a r e
solitary
were o c c a s i o n a l l y n e a r e a c h o t h e r
of
extended
sociality
animals.
in this
study,
i n v o l v e d f e m a l e s and
Although
the
their
only
lynx
signs
young o f
the
year.
The
degree
carnivores
prey
size
solitary
and
hunting
while
in
relatively
large
sociality
in
typically
prey,
lions
hypothesis
Lynx
this
1983,
often
been
dense
for
used
to
explain
1972,
in lions
that
capturing
Bertram
Kruuk's
test
of
Packer
r e s u l t s from
for large prey,
i n w h i c h t h e y l i v e and
3)
the
2)
high
attain.
boreal
snowshoe h a r e s w h i c h w e i g h o n l y
that
than
suggest
inconclusive.
f a c t o r s : 1) p r e f e r e n c e
habitat
smaller
to
Kruuk
1983).
sociality
preferred
s e l e c t larger prey.
adaptation
f o r f e l i d s , h o w e v e r , was
of
(1963) n o t e d
animals
1972,
Macdonald
d e n s i t i e s which they
inhabit
on
has
(Schaller
populations
a f u n c t i o n of
observation
an
suggests instead that
o p e n e s s of t h e
population
prey
is
and
in
Bouliere
carnivores
carnivores
a c o m b i n a t i o n of t h r e e
the
t o be
developed t h i s
1978,1979, G i t t l e m a n
(in press)
observed
strategy.
social
( 1 9 7 2 , 1975)
sociality
this
sociality
i s generally considered
carnivores
themselves
Kruuk
of
f o r e s t s and
consume p r i m a r i l y
10-15% of t h e a d u l t body
weight
73
of
a
lynx.
The r e l a t i v e l y
dense b o r e a l
Further,
f o r e s t would t h e r e f o r e not favor
Kleiman and E i s e n b e r g
stealth,
the
solitary
primary
life
style.
lynx can reach
It
for
is
lynx
that
hunting
high
rates
family
disadvantage
snowshoe
benefit
capture
hare
group l i v i n g
demands
l a r g e r prey items,
such
success,
(1983) found
chases
that
Why
and four
open
coordinate
group hunts f o r
visibility
habitat
is
but
(Peterson
use
1977).
Based
study
on
i n lynx during
group
caribou,
living
Dall
be
periods of
might
them t o
sheep
i n dense cover w h i l e
animals
and
prey
in
dense
Wolves hunt c o o p e r a t i v e l y
vocalizations
lions are
a n d i t may n o t be p o s s i b l e t o
large
to
cover
where
i n closed
forest
their
efforts
coordinate
L y n x do n o t v o c a l i z e .
the
high
d e g r e e o f home r a n g e o v e r l a p ,
were n o t t e r r i t o r i a l .
a limiting
then
low.
were
l y n x a r e n o t s o c i a l may be r e l a t e d t o
Lynx l i v e
country
are
T h e r e may t h e r e f o r e
Further,
as
a
however,
l y n x when snowshoe a b u n d a n c e i s . l o w by e n a b l i n g
typically
space
et a l .
of
respectively.
by
t o those of l i o n s .
Parker
(percent
abundance.
Packer's second p o i n t .
if
lynx,
u n i t s of one, two, t h r e e
to
p e r h a p s moose c a l v e s .
this
hunting
t o note, however, t h a t h u n t i n g
17, 38 a n d 58 p e r c e n t
little
of
d e n s i t i e s equal
w i t h group s i z e .
success
for
strategy
that
i n lynx.
In areas of h i g h prey abundance,
population
increases
sociality
(1973) suggest
hunting
interesting
successful)
14,
s m a l l s i z e of l y n x p r e y and l i f e i n
resource
As d i s c u s s e d
i s s t a b l e and
by D a v i e s
predictable
i t i s t o the advantage of the predator
e x c l u s i v e use a r e a s
(territories).
If
the
in
lynx i n
(1978),
time
and
t o t o defend
resource
i s not
74
stable
and
predictable
i n t i m e a n d s p a c e , h o w e v e r , t h e r e i s no
benefit t o defending a t e r r i t o r y
i n which the resource i s l i k e l y
to d i s a p p e a r .
Territoriality
several
felid
(Bailey
within
species.
sexes,
Female t i g e r s
1979: c i t e d
cheetahs
males.
being
to
resource
defend
i n these
by
these
b e t w e e n s e x e s i s common
overlap
has
been
European
bobcats
wildcats
(Schaller
1972)
against
considered
in
reported
wildcats
felids.
cougars
(Corbett
are
other
to
also
been
c o a l i t i o n s of
be
the
resource
Home r a n g e
Male-female
fortigers
be
C o a l i t i o n s o f male
male c o a l i t i o n s .
( S c h a l l e r a n d Crawshaw 1 9 8 0 ) ,
1973) ,
European
systems.
territories
Females a r e g e n e r a l l y
defended
and
for
Food i s g e n e r a l l y c o n s i d e r e d t o
(Frame 1980) a n d l i o n s
reported
described
i n P a c k e r i n p r e s s ) have been r e p o r t e d t o
h a v e e x c l u s i v e home r a n g e s .
defended
been
( S u n g u i s t 1981),
1974), l e o p a r d s (Bertrum 1982),
(Corbett
the
have
overlap
home
range
( S u n g u i s t 1981), j a g u a r s
(Seidensticker
et a l .
1979), and b o b c a t s
(Bailey
1974) .
Snowshoe h a r e
populations,
numbers,
at
the
months o f t h e s t a r t
would
be
limiting
resource
for
lynx
a r e u n s t a b l e i n both time and space and a r e l i k e l y
unpredictable to the lynx.
densities
the
cyclic
Areas
peak
which
may
of t h e d e c l i n e .
may
have
be v i r t u a l l y
Under t h e s e
high
empty
hare
within
conditions
i t
m a l a d a p t i v e f o r a l y n x t o expend energy m a i n t a i n i n g a
territory.
I n summary, snowshoe h a r e a b u n d a n c e a n d
to
be
the
proximate
structuring
forces
distribution
seem
controlling
lynx
75
a b u n d a n c e and d i s t r i b u t i o n .
function
lag
of
A b s o l u t e abundance
snowshoe h a r e a b u n d a n c e .
b e h i n d t h o s e o f h a r e s by
Nicholson
one
1942, B r a n d e t a l .
space
to
of
Cycles i n lynx
two
years
(
1976, P a r k e r e t a l .
Elton
1983 ).
distribution.
Lynx c o n c e n t r a t e i n a r e a s of r e l a t i v e l y h i g h
et
1979 and t h i s
a l .
1963a, B e r g e r u d
on
1971, B e r r i e
s t u d y ) and d i s p e r s e a f t e r
a
abundance
in
(Saunders
dependent
is
distribution
abundance
is
lynx
snowshoe
1974,
and
Lynx
hare
hare
Koehler
these areas of
r e l a t i v e a b u n d a n c e have been d e p l e t e d ( t h i s s t u d y ) .
76
MANAGEMENT IMPLICATIONS
Introduct ion
E f f e c t i v e management
marked
fluctuations
plans
that
vary
recruitment
in
of
recruitment
harvest
rate.
rate
Failure
p e r i o d s of low r e c r u i t m e n t
to
increase
wildlife
when
populations
rates
directly
to
exhibiting
r e q u i r e management
with
changes
reduce t h e harvest
can i n h i b i t
c o n d i t i o n s again
in
rate during
the populations
become f a v o u r a b l e
ability
(Caughley
1977).
Recruitment
of l y n x i n t o
the population
from
z e r o d u r i n g p e r i o d s o f l o w snowshoe h a r e a b u n d a n c e t o 3 t o
near
4 young
per
abundance.
however,
rate.
female
per
year
during
periods
do
not
take
loss
In
addition,
s t u d i e s , suggests
of
over
evidence
55% of l y n x p o p u l a t i o n s .
and
scarcity
figures.
found annual
from
this
During
During
2 years
to
be
produced
e f f e c t of t h e observed
2
harvest
annual
of
trapping
higher
than
of d e c l i n i n g hare abundance, I
m o r t a l i t y r a t e s o f 100 a n d 75 p e r c e n t
therefore
to
and p a s t
periods
i n snowshoe h a r e a b u n d a n c e b o t h
l y n x w h i c h were known t o l e a v e K l u a n e Game
I
susceptible
Other f a c t o r s cause t h e
n a t u r a l m o r t a l i t y r a t e s c a n be e x p e c t e d
these
hare
i n recruitment
t h a t man i s r e s p o n s i b l e f o r an
l o s s o f 5.6% o f l y n x p o p u l a t i o n s e a c h y e a r .
decline
high
used f o r l y n x ,
i n t o account f l u c t u a t i o n s
Lynx p o p u l a t i o n s a r e t h e r e f o r e e s p e c i a l l y
tagging
of
Management s t r a t e g i e s c u r r e n t l y b e i n g
over-harvesting.
and
fluctuates
simulation
o f my
tagged
Sanctuary.
models t o a s s e s s t h e
r a t e s on l y n x p o p u l a t i o n
dynamics
77
through t h e i r
ten year
cycle.
The
Models
I developed the models,using p o p u l a t i o n
6)
from
my
work
parameters
and t h a t o f B r a n d and K e i t h
m o d e l s I s u b d i v i d e d t h e snowshoe h a r e c y c l e
h a r e abundance, 2 y e a r s of i n t e r m e d i a t e
(1979).
(Table
In both
i n t o 3 y e a r s of h i g h
hare
abundance
during
i n c r e a s e and d e c l i n e p h a s e s and 3 y e a r s o f low h a r e a b u n d a n c e a t
the
bottom of the c y c l e .
population.
7%
I assumed a 1:1
I set the i n i t i a l
yearlings
and
93%
adults,
f o u n d by B r a n d and K e i t h
abundance
the
and
just
hare c y c l e .
prior
hare
(1979).
of
after
t o the s t a r t
years
I allowed kittens
season
abundance.
100% s u r v i v a l
(May
low
model
A
(see
low,
pregnancy
intermediate
and
Keith
high
s u r v i v a l d u r i n g p e r i o d s of
from
Brand
and
respectively.
1a f o r d e t a i l s o f t h e m o d e l ) ,
yearling
and
c a l c u l a t e d by t h e e q u a t i o n :
= (NY * .5 * RY)
of
t o November) d u r i n g p e r i o d s o f
appendix
by
hare
start
E s t i m a t e s of k i t t e n
annual k i t t e n production
NK
of
from b i r t h t o the
(1979) and s e t a t 35 and 8 %
In
distribution
s i z e and
i n t e r m e d i a t e and low h a r e a b u n d a n c e were t a k e n
Keith
at
of t h e i n c r e s e phase
E s t i m a t e s o f in u t e r o l i t t e r
females at
lynx
distribution
t o t h e age
3
i n the
a b u n d a n c e were t a k e n f r o m T a b l e 5 o f B r a n d and
the trapping
hare
l y n x age
similar
(1979)
r a t e s f o r y e a r l i n g and a d u l t
high
spring
sex r a t i o
+ (NA * .5 *
RA)
adult
females
was
78
T a b l e 6.
Parameter e s t i m a t e s used i n l y n x p o p u l a t i o n
s i m u l a t i o n models.
A d u l t and y e a r l i n g m o r t a l i t y r a t e s
are per year.
K i t t e n summer m o r t a l i t y r a t e s a r e b i r t h
t o November.
P o s t November k i t t e n m o r t a l i t y r a t e s were
assumed e q u a l t o a d u l t m o r t a l i t y r a t e s .
Lynx pregnancy
r a t e s , l i t t e r s i z e s , k i t t e n m o r t a l i t y r a t e s and a d u l t
m o r t a l i t y r a t e s f o r model B a r e from Brand and K e i t h
(1979).
I assume l y n x have a maximum o f 1 l i t t e r p e r
year.
See t e x t f o r d e r i v a t i o n o f a d u l t m o r t a l t y r a t e s
f o r m o d e l A.
PARAMETER
SNOWSHOE HARE ABUNDANCE
LOW
INTERMEDIATE
HIGH
Adult lynx
pregnancy
rate
0.33
0.46
0.7 3
Y e a r l i n g lynx
pregnancy
rate
0.0
0.0
0.4
Adult lynx
in utero
l i t t e r size
3.4
3.9
4.6
Y e a r l i n g lynx
in utero
l i t t e r size
3.9
Lynx k i t t e n
summer
mortality rate
0.92
0.65
0.0
Trapping
mortality rate
( m o d e l A)
0.55
0.55
0.55
Natural
mortality rate
( m o d e l A)
0.06
0.06
0.06
Trapping
mortality rate
( m o d e l B)
0.14
0.14
0.14
Natural
mortality rate
( m o d e l B)
0.35
0.35
0.35
80
where
*
= m u l t i p l i e d by
NK = number o f k i t t e n s i n t h e f a l l ;
NY = number o f y e a r l i n g s
i n the spring
RY = p r e g n a n c y r a t e * i_n u t e r o
litter
f e m a l e s * summer s u r v i v a l r a t e
NA = number o f a d u l t s
all
assumed
that
age c l a s s e s
occurred
mortality
in
population;
litter
f e m a l e s * summer s u r v i v a l r a t e
I
size for yearling
forkittens;
i n the spring
RA = p r e g n a n c y r a t e * i_n u t e r o
population;
size f o r adult
for kittens
November t o May m o r t a l i t y r a t e s were e q u a l f o r
and
this
that
a l l yearling
period.
rates.
I
set
and
adult
I assumed no d e n s i t y
annual
trapping
and
mortality
dependence i n
non-trapping
mortality
r a t e s a t 5 5 % a n d 6% r e s p e c t i v e l y ( s e e p r e v i o u s
on
mortality
lynx
trapping
season
for derivation
(May)
adult
lynx
c a l c u l a t e d by t h e e q u a t i o n :
NAS = (NAF + NYF) * S
where
*
= m u l t i p l i e d by
NAS = number o f a d u l t s
i n May
NAF = number o f a d u l t s
i n November
NYF = number o f y e a r l i n g s
S
i n November
= s u r v i v a l r a t e November t o May
of
these
population
section
values).
Post
numbers
were
81
May
yearling population
NYS
= NKF
*
numbers was
c a l c u l a t e d by
the
equation:
S
where
NYS
= number o f y e a r l i n g s
NKF
= number of
B r a n d and
population
contained
in
kittens in
Keith
spring;
fall;
(1979) a l s o m o d e l l e d t h e
through
a
decline
t o the
s e v e r a l q u a l i t a t i v e and
effect
on
the
d y n a m i c s of
the
model
A
to
reflect
a s s u m p t i o n s and
model
(1979)
of
kitten
modelled
from
would have
population,
recruitment
same i n m o d e l s A and
assumed
a d d i t i v e and
that
that
B r a n d and
trapping
mortality
mortality
l o s s e s at
As
I
1b
for
an
modified
parameter estimates
Keith
details
of
of
35%
and
lynx
population
B r a n d and
Keith
non-trapping mortality
age
( 1 9 7 9 ) , h o w e v e r , assumed t h a t a l l
non-
from
May
similar
the
in
t o November.
annual m o r t a l i t y at
model.
of
was
were
all
occurred
first
i n t o the
i n m o d e l A,
mortality
(1979) e s t i m a t e d ' t o t a l
v a l u e u s e d i n my
B.
trapping
trapping
classes.
the
Model A
B).
the
Keith
i f these d i f f e r e n c e s
(1979)(Table 6)(see appendix
Calculation
was
the
lynx
quantitative differences
model.
Keith
determine
f o l l o w i n g peak.
their
B r a n d and
To
d y n a m i c s of a
44%,
Brand
s i m i l a r to
They e s t i m a t e d a n n u a l
spring
lynx
and
natural
population
and
82
trapping
mortality
at
14%
therefore
c a l c u l a t e s independent estimates
y e a r l i n g a n d a d u l t numbers
of
using
the
fall
their
population.
Model B
for spring
estimates
and
fall
of t r a p p i n g
and
non-trapping mortality rates.
Results
I
ran
both
starting with
lynx
models
high
5 complete c y c l e s
phase
hare
i n m o d e l A was v i r t u a l l y
c y c l e o f 10 y e a r s
(Fig.
12).
extinction
natural)
studies
In
when
were
the
total
0.30
or
Even d u r i n g
Parker
1983,
Nellis
et a l .
i n excess of
is
to v i r t u a l
(trapping
A l lpast
Mech
1980,
Carbyn
and
+
tagging
(this
Patriquin
1979) have
reported
0.30.
i n model B
also
declined
to
virtual
a l t h o u g h a t a slower r a t e than i n model A ( F i g 14).
interesting
simulation
rates
13).
of
i n t o the lynx
declined
1972, K o e h l e r e t a l .
The l y n x p o p u l a t i o n
extinction,
(Fig.
periods
determine annual m o r t a l i t y rates
1983,
et a l .
mortality
larger
The
e x t i n c t a t t h e end o f
lynx population
annual
f o r which I could
study,
rates
fact
(50 y e a r s )
abundance.
hare abundance m o r t a l i t y exceeded r e c r u i t m e n t
population.
It
through
2 y e a r s of i n c r e a s e
population
one f u l l
and P i s c u s s i o n
from
the
to
note
start
that
of
i n Brand and K e i t h
the
cyclic
decline
(1979)'S
in
a b u n d a n c e t o t h e f o l l o w i n g peak i n a b u n d a n c e , 8 y e a r s l a t e r ,
modelled
lynx
approximately
a
number
decline.
population
0.4%.
This
of c y c l e s t h e i r
showed
a
decline
suggests t h a t , allowed
population
may
in
numbers
t o run
lynx
the
of
through
a l s o have c o n t i n u e d
to
83
Figure
12.
D y n a m i c s o f s i m u l a t e d l y n x p o p u l a t i o n u s i n g model
A and o b s e r v e d m o r t a l i t y r a t e s .
See T a b l e 6 a n d
A p p e n d i x 1a f o r p a r a m e t e r e s t i m a t e s a n d s i m u l a t i o n model
program.
84
azis NOiivnndOd
85
Figure
13.
Dynamics of s i m u l a t e d l y n x p o p u l a t i o n u s i n g model
A w i t h t o t a l a n n u a l m o r t a l i t y r a t e s e t a t 0.30.
See
T a b l e 6 and A p p e n d i x 1a f o r p a r a m e t e r e s t i m a t e s a n d
s i m u l a t i o n model p r o g r a m .
o
in
o
o
CO
CO
<
LU
>
o
CM
87
Figure
14.
D y n a m i c s o f s i m u l a t e d l y n x p o p u l a t i o n u s i n g model
B a n d m o r t a l i t y r a t e e s t i m a t e s f r o m B r a n d and K e i t h
(1979).
See T a b l e 6 and A p p e n d i x 1b f o r p a r a m e t e r
e s t i m a t e s and s i m u l a t i o n model program.
88
CO
cc
<
UJ
>-
3Zis NOiivnndOd
89
L y n x p o p u l a t i o n s i n n a t u r e c e r t a i n l y do n o t d e c l i n e a t
rate
indicated
decline
lynx
by
these
that
are
r a t e s t h a t are too h i g h .
population
litter
sizes
collected
are
found
from
founded.
Keith
The
i n s i m u l a t e d p o p u l a t i o n s must r e s u l t
recruitment
lynx
simulations.
too low,
My
Brand
trappers.
and
(1979)
therefore
that
e s t i m a t e s of m o r t a l i t y
my
November)
I
assumed no
clearly
erring
actually
be
rates
2) t r a p p i n g and
kitten
to
and
be
well
models:
first
1)
kitten
t r a p p i n g season
non-trapping
mortality
mortality.
kitten
in
carcasses
Two
(May
initial
i_n u t e r o
r a t e s are too high.
from b i r t h t o the s t a r t of t h e i r
following
on
the
and
mortality
arid
into
Brand
included in
my
mortality
favor
of
at
higher
occurring i n nature.
high
hare
abundance,
recruitment
Estimates
than
of k i t t e n
could
mortality
at
i n t e r m e d i a t e and
low h a r e a b u n d a n c e s were d e r i v e d
B r a n d and
K e i t h (1979) and
set
Kitten mortality
r a t e s may
abundance
those
s t u d i e s do,
during
I , saw
periods
a l s o found
during
however,
periods
( 1 9 7 9 ) and
during
than
of
of
of
low
at
and
Evidence
abundance.
of
92%
kittens
hare abundance.
kittens
hare abundance.
kitten
Both
on
our
carcass
During
hare
other
survival
B r a n d and
B r a n d and
in
low
f r o m t h i s and
low
from
respectively.
i n t e r m e d i a t e and
extremely
hare
3 percent
low
65
lower
suggest
no e v i d e n c e
l e s s than
periods
be
at
estimated.
low
of
mortality
in
seem
both
rapid
estimates
or e s t i m a t e s of
Keith
They
components of m o r t a l i t y are
to
from
e s t i m a t e s of r e c r u i t m e n t
It i s therefore likely
(1979)'s
surprisingly
b a s e d on p r e g n a n c y r a t e s , and
by
the
Keith
study
areas
Keith
(1979)
collections
p e r i o d s of
high
90
hare abundance, k i t t e n s c o m p r i s e d
18 t o 30
samples.
with
In
intermediate
continue
any
event,
even
and low hare
two
be
reasons.
6
rate
survival at
should
These e s t i m a t e s
these estimates
may be t o o h i g h f o r
a r e b a s e d on a t o t a l
from
into
s u g g e s t s t h a t low sample s i z e
may
be
The f a c t
the
the
population
most
ease, f i e l d
sustain,
i s not t h e complete answer.
mortality
representative
often
rates
of
observed
mortality
in
rates
s t u d i e s on l y n x , a s w i t h o t h e r
undertaken
in
areas
of
is
be
most
intense.
i n areas
reasons
mammals,
relatively
T h e s e a r e a l s o t h e a r e a s where t r a p p i n g
to
these
For
accessibility.
likely
high
pressure
Trapping m o r t a l i t y rates i n
r e m o t e a r e a s where a c c e s s i s l i m i t e d may be f a r l o w e r .
trapping
mortality
considerably
accessiblity.
less
If
extremely important
declines
and
rates
over
than
those
this
i s the
i n maintaining
Average
l a r g e a r e a s w o u l d t h e r e f o r e be
noted
in
areas
of
high
c a s e , r e m o t e a r e a s may be
lynx populations
lows i n hare abundance.
areas i n maintaining
that
mortality
could
t o those i n which t h e s t u d i e s took p l a c e .
logistic
36
w h i c h t h e s e 36 a n i m a l s were drawn a l l h a d
recruitment
Alternatively,
of
therefore
r a t e s i n e x c e s s o f 0.30, t h e maximum a n n u a l
that
studies
from t h i s and
The h i g h m o r t a l i y r a t e s o b s e r v e d m i g h t
studies
similar
trapped
populations
i n model A were d e r i v e d
studies.
First,
lynx.
mortality
are
kitten
due t o random c h a n c e w i t h i n t h e s m a l l s a m p l e .
the
of
lynx
of
t o d e c l i n e under t h e observed m o r t a l i t y r a t e s .
lynx tagging
tagged
100%
abundance,
Adult m o r t a l i t y rates
past
percent
lynx populations
during
the
The i m p o r t a n c e o f remote
through
periods
of
low
91
recruitment
continually
was
may
be
throughout
unsustainable
maintaining
suggested
i n c r e a s i n g access
populations
rates
first
into
large
harvest
parts
rates.
(Parker
1983,
was
et
B r a n d and
(1977) s u g g e s t e d
vary
of
The
al.
their
With
areas,
range
resulting
n e e d s more
has
of
lynx
and
1983,
by
several
Carbyn
B e r r i e 1974).
of l y n x .
i n t o the h a r v e s t a b l e
for
populations
Researchers
to
(1974),
i n an
populations
allowed
the
publication
insightful
in
Alaska,
f o r as much a s
abundance.
He
areas
and
continued
result
i n a decreased
of
discussion
recommended
3 years
suggested
dynamics
recommending
2
trapping
cyclic
K e i t h (1979) r e i t e r a t e d
v
through
future
no
Berrie
of
lynx
lynx trapping
cyclic
low
to
reducing
in
low
hare
would
t h e number of
when c o n d i t i o n s i m p r o v e d .
and
untrapped lynx
i n c r e a s e i n the
one
complete
total
be
wilderness
throughout the c y c l i c
by
years
Brand
t h i s recommendation w i t h the h e l p
T h e i r m o d e l s i n d i c a t e d a 28%
population
the
that
d u r i n g the
amplitude
s i m u l a t i o n m o d e l s of t r a p p e d
lynx
of
(1977) book.
t h a t w i t h improved access
i n d i v i d u a l s a v a i l a b l e t o breed
and
Caughley's
rates
population,
with
were i n f a c t
and
Caughley
a t r a c k i n g s t r a t e g y f o r t h e h a r v e s t i n g of l y n x p o p u l a t i o n s
prior
in
populations
been e x p r e s s e d
Todd
K e i t h 1979
the o n l y workable s t r a t e g y
in
research.
t h a t a " t r a c k i n g s t r a t e g y " , where h a r v e s t
to those
lynx
i m p o r t a n c e of remote a r e a s
1983,
d i r e c t l y with recruitment
similar
(1974).
remote
existance
i n t e n s i v e trapping pressure
Patriquin
these
lynx populations c l e a r l y
researchers
Berrie
s u b j e c t e d t o u n i f o r m l y h i g h human m o r t a l i t y
Concern f o r the c o n t i n u e d
under
by
of
populations.
harvestable
c y c l e i f t r a p p i n g were
92
c u r t a i l e d during
low.
Parker
the three
et a l .
years of lynx p o p u l a t i o n
(1983) n o t e d t h a t t h e l y n x h a r v e s t
S c o t i a was c u r t a i l e d d u r i n g
and
low
recruitment
curtailment
lynx
trapping
The
underlying
the
harvest
researchers,
otherwise
assumption
plans
when
f o r lynx
That
conditions
of
low
during
periods
causes
anyway
the
low
improved.
of
strategy,
by
previous
additive
in
hare
would
abundance
to
mortality
during
I n d i v i d u a l s which a r e trapped
conditions
would
improved.
die
of
natural
Trapping m o r t a l i t y ,
o f i t , w o u l d t h e r e f o r e h a v e no e f f e c t on
individuals
to
A l t e r n a t i v e l y , trapping
o f low p r e y a v a i l a b i l i t y
some p r o p o r t i o n
number
prey abundance.
before
the c y c l i c
i s , lynx that are trapped
m o r t a l i t y may be c o m p e n s a t o r y f o r n o n - t r a p p i n g
periods
curtailment
numbers.
recommended
mortality.
future
i n t o lynx
i n Caughley's t r a c k i n g
s u r v i v e through the
reproduce
a case f o r
i s that trapping m o r t a l i t y i s l a r g e l y
non-trapping
or
during
i n Alberta f o r 3 to 4 years during
d e c l i n e and low i n l y n x p o p u l a t i o n
and
scarcity
He recommended
be c o n t i n u e d
Todd (1983) a l s o p r e s e n t e d
and
i n Nova
hare
o f snowshoe h a r e s c a r c i t y a n d l o w r e c r u i t m e n t
populations.
of
a p e r i o d o f snowshoe
i n t o the lynx population.
t h a t a system of harvest
periods
decline
surviving
to
breed
when
the
conditions
improved.
In o u r s i m u l a t i o n s
both
Brand
and
Keith
t r a p p i n g m o r t a l i t y were
supported
this
r e s i d e n t on t h e i r
of the
(1979)
area
of
lynx
populations,
a n d I assumed t r a p p i n g a n d n o n -
additive
assumption
study
dynamics
with
.
Brand
the
and
Keith
observation
a t t h e e n d o f one
that
trapping
(1979)
lynx
season
93
but
the
were n o t
present
the
following winter.
l y n x must have d i e d d u r i n g
was
the
summer
and
their
therefore a d d i t i v e to trapping m o r t a l i t y .
t o assume t h a t a l l n o n - t r a p p i n g
trapping
It
occurred
during
mortality
would
be
during
the
In
the
surprising
my
most
if
benign
study,
42%
a l l
time
of
occurs
mortality
extrapolate
outside
occurred
during
then,
that
the
i n B r a n d and
from
the
area
l y nx
the
the
Keith's
Keith
mortality
up
gain
harvestable
in
by
t o 50%
the
low
lynx
low
a l l
It is possible
dispensed
A l s o , t h e d e a t h of
through
a
trapping during
If this
one
i n hare
cyclic
of
my
abundance
low
in
hare
natural
the
mortality
may
3 years
be
mortality during
i s the c a s e ,
of
lynx
a
net
complete c y c l e would
continuing
of
populations
when
low
more
be
lynx
than
50%
of
low
to harvest
lynx
periods
i n hare abundance would have l i t t l e
recovery
and
(1979) s t u d y
the
to
dispersed
(1979)'S model s u g g e s t e d t h a t w i t h
compensatory f o r non-trapping
through the
lynx
May
trapping.
Trapping
hare abundance.
from
compensatory f o r t r a p p i n g m o r t a l i t y ,
curtailing
recruitment.
mortality
abundance
a l l lynx would s u r v i v e the
abundance even w i t h o u t
and
year
hare
l y n x , presumably to s t a r v a t i o n , during
Brand
of
snow-free p e r i o d .
rather than d i e d .
s u g g e s t s t h a t not
non-trapping
radio-tagged
p e r i o d of r a p i d d e c l i n e i n
dispersal
achieved
They
that
season.
November.
on
They c o n c l u d e d
o r no a f f e c t
hare
abundance
increased.
Therefore,
Keith
(1979)
although
and
I applaud
others
who
the
efforts
of
Brand
and
have a t t e m p t e d t o d e v e l o p sound
.94
management schemes f o r l y n x , i t w o u l d be p r e m a t u r e t o
these
'plans
without
p l a n c a n o n l y be
confines
of
a
determined
sound
s e t t i n g up r e p l i c a t e
trapped
further testing.
study
continuously,
period
Keith
of
low
i t
lynx
conducted
design.
areas.
as
The e f f e c t i v e n e s s o f any
is
experimental
One
under c u r r e n t
l y n x , and i n t h e second a r e a
the
i f
within
This would
study
area
( 1 9 7 9 ) ' S management p l a n .
as suggested
By m o n i t o r i n g
lynx
harvest
i n the 2 areas the e f f e c t i v e n e s s of " t r a c k i n g
assessing
(Romesburg
assessed.
the
This
effectiveness
1981, W a l t e r s
type
of
during
recruitment
m o r t a l i t y r a t e s and t o t a l
of experiment
any
and H i l b o r n
be
i n B r a n d and
t r a p p i n g and n o n - t r a p p i n g
be
entail
would
t r a p p i n g w o u l d be c u r t a i l e d
recruitment
the
management schemes f o r
rates,
could
impliment
new
1976).
lynx
strategy"
i s essential in
management
strategy
95
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1 02
APPENDIX
103
Appendix
1a.
P r o g r a m f o r s i m u l a t i o n m o d e l A. P r o g r a m i s w r i t t e n
i n BASIC f o r A P P L E l i e m i c r o c o m p u t e r a n d c o m p i l e d
w i t h m i c r o simcon p o p u l a t i o n s i m u l a t i o n package
( W a l t e r s 1 9 8 2 ) . See T a b l e 6 f o r p a r a m e t e r e s t i m a t e
and t h e i r d e r i v a t i o n .
100
IF T l > 0 THEN 200
105 T = .55:N = .06: REM
T=TRAPP
ING MORTALITY RATE AND N= NA
TURAL MORTALITY RATE
110 NY = 7:NA = 93: REM
NY= NUMB
ER OF YEARLINGS IN I N I T I A L P
•PULATION AND NA = NUMBER OF
ADULTS IN I N I T I A L POPULATIO
N
120 A = 0
200
IF A ^
= 1 THEN 207
201
= 4 THEN 2
,IF A > 1 AND A <
06
IF A > 4 AND A <
202
= 6 THEN 2
07
IF A > 6 AND A <
204
= 9 THEN 2
08
205 : REM IN LINES 206 TO 208 RY
=AVERAGE NUMBER OF KITTENS P
RODUCED PER YEARLING FEMALE
PER YEAR; RA = AVERAGE NUMBE
R OF KITTENS PRODUCED PER AD
ULT FEMALE PER YEAR
206 RY = 1.6:RA = 3.4: GOTO 210
207 RY = 0:RA = .6: GOTO 210
208 RY = O:RA = .1
210 NK = NY * .5 * RY + NA * .5 *
RA: REM
NK=YEARS PRODUCTION
OF KITTENS
220 NA = NY + NA - (NY + NA) * (T
+ N)
230 NY = NK - NK * (T + N)
240 NT = NY + NA: REM
NT= TOTAL
PRE-BREEDING SEASON POPULATI
ON
241
IF A <
= 9 THEN A =
242
I F A > 9 THEN A = 0
250 Z ( 1 , T I ) = NT
251 Z ( 2 , T I ) = NA
Z(3,TI> = NY
253 Z ( 4 , T I )
NK
=
105
Appendix
lb.
P r o g r a m f o r s i m u l a t i o n m o d e l B. P r o g r a m i s w r i t t e n
i n BASIC f o r APPLE l i e m i c r o c o m p u t e r and c o m p i l e d
w i t h m i c r o simcon p o p u l a t i o n s i m u l a t i o n package
( W a l t e r s 1 9 8 2 ) . See T a b l e 6 f o r p a r a m e t e r e s t i m a t e
and t h e i r d e r i v a t i o n .
100
IF T I > 0 THEN 200
105 T = 0.14:N = 0.35: REM
T= TR
APPING MORTALITY RATE AND N=
NATURAL MORTALITY RATE
110 NY = 7:NA = 9 3 : REM
NY=NUMBE
R OF YEARLINGS IN I N I T I A L PO
PULATION AND NA=NUMBER OF AD
ULTS IN I N I T I A L POPULATION
120 A =.0
200
IF A < = 1 THEN 207
201
I F A > 1 AND A < = 4 THEN 2
06
202
IF A > 4 AND A < = 6 THEN 2
07
204
IF A > 6 AND A < = 9 THEN 2
OB
205 : REM
IN LINES 206 TO 208 RY
=AVERAGE NUMBER OF KITTENS P
RDDUCED PER YEAR PER YEARLIN
G FEMALE AND RA= AVERAGE NUM
BER OF KITTENS PRODUCED PER
ADULT FEMALE PER YEAR
206 RY = 1.6:RA = 3.4: GOTO 210
207 RY = 0:RA = .6: GOTO 210
208 RY = 0:RA = .1
210 NK = NY * .5 * RY + NA * .5 *
RA: REM
NK= YEARS PRODUCT10
N OF YOUNG
215 NA = NA - (NA * N ) : REM
CALC
ULATION OF ADULT POPULATION
PRIOR TO TRAPPING SEASON
217 NY = NY - (NY * N ) : REM
CALC
ULATION OF YEARLING POPULATI
ON PRIOR TO TRAPPING SEASON
220 NA = NA + NY - (NA + NY) * T:
REM
CALCULATION OF POST TR
APPING SEASON ADULT POPLUATI
ON
230 NY = NK - NK * ( T ) : REM
CALC
ULATION OF POST TRAPPING SEA
SON YEARLING POPULATION
240 NT = NY + NA: REM CALCULATIO
N OF TOTAL POPULATION S I Z E I
N SPRING
241
IF A < = 9 THEN A = A + 1
242
I F A > 9 THEN A = O
250 Z ( 1 , T I ) = NT
251 Z ( 2 , T I ) = NA
252 Z ( 3 , T I ) = NY
253 Z ( 4 , T I ) = NK