Postglacial Distribution Patterns of Mammals in the Southern Coastal Regions of Alaska
Author(s): David R. Klein
Source: Arctic, Vol. 18, No. 1 (Mar., 1965), pp. 7-20
Published by: Arctic Institute of North America
Stable URL: http://www.jstor.org/stable/40507335 .
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Papers
POSTGLACIAL DISTRIBUTION PATTERNS OF
MAMMALS IN THE SOUTHERN COASTAL
REGIONS OF ALASKA*
David R. Kleinf
the Wisconsinglaciationthe presentland areas of the coastal
regionsof Alaska borderingthe Gulf of Alaska were virtuallycompletelyoverriddenby ice. The now existingfloraand fauna of the region
becomeestablishedin the 10,000yearssincethe recession
have presumably
of the ice.
Swarthdiscussedthe originsof the fauna of the "Sitkan District"in
1936,and since then additionalknowledgeof the glacial historyof the
a new
southerncoastalregionsof Alaska has becomeavailable,permitting
of
the
of
mammals
distribution
interpretation
patterns
(Heusser1960,Miller
and
Karlstrom
The
ofmammals
Flint
distribution
1957,
present
1958,
1964).
of
inthisregion,althoughcomplicated
the
reflects
by
phenomenon insularity,
the sequenceof theirarrivaland theirrelationship
to specificrefugia.
A briefreviewofthelate-Wisconsingeologyand postglacialvegetation
of the southerncoastal areas of Alaska will serve as a useful base for
the mammaliandistribution
patternsof the region.Heusser
understanding
has
the
shown
that
ice, coveringvirtuallyall this region,receded
(1960)
about 10,000years ago. The islands of the AlexanderArchipelagowere
apparentlyfree of ice at least a few hundredyears beforethe adjacent
mainlandwhereasin PrinceWilliamSound, on the Kenai Peninsula,and
on Kodiak Island glacial recessiontook place approximately1,000-2,000
yearslaterthanin theAlexanderArchipelago.In the intervening
regionof
the mainland,fromMt. Fairweatherto Cape Suckling,late-Wisconsin
ice
did notcovermuchmoreland thanis now occupiedby glaciers
apparently
has been a complicating
factorin this
althoughmajorpostglacialtectonism
area (Miller 1958).
As the ice melted,associatedchangesin sea-leveltook place. In the
AlexanderArchipelagoit is probable that duringthe Wisconsinglacial
maximum,sea-levelwas lower than at present,exposinggreaterexpanses
AlaskanScienceConference,
at theFourteenth
August29, 1963,
♦Paperpresented
Alaska.
Anchorage,
ResearchUnit,College,Alaska.
Wildlife
fAlaskaCooperative
7
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8
POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
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POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
9
of land,creatingconnections
betweenislandsand mainland,and narrower
channelsbetweenislands. This situationprobablycontinuedfor a short
timeaftertheice had leftthisregionbeforethe greatcontinental
ice sheet
withits large volumeof storedwater had decreasedsignificantly
in size
ice sheetmelted,the sea-levelrose
(Flint 1957). Later,as the continental
The rise of sea-levelwas offsetin some regionsby crustal
considerably.
of
upwarping the land followingthe removalof the load of ice fromthe
land. In the Juneau,Lituya Bay, and Katalla areas beach terraceshave
been found30-100m. above presentsea-level,but in the regionof Prince
WilliamSound sea-landrelationships
appear not to have greatlychanged
sincethe recessionof ice (Heusser 1960).
Followingice recession,land areas rapidlybecamevegetated.Heusser's
indicatethatalder,ferns,sedges,and willows
(1960) polleninvestigations
were dominantvegetationtypesimmediatelyfollowingthe ice recession,
a floralcomplexperhapssimilarto thatof the presenttreeless
constituting
areas oftheAlaska Peninsula.In theAlexanderArchipelagolodgepolepine
(Pinus contorta)was the dominantearly tree species. With the gradual
ofsoilsthepinewas replacedon thebettersitesby Sitkaspruce
development
(Picea sitkensis) and mountainhemlock (Tsuga mertensiana)
; more
westernhemlock(T. heterophylla)
has becomea dominantmember
recently
of the forestsof the region.
Fromthe end of the Wisconsinglaciationto the present,access to the
southerncoastalregionof Alaska by mammalshas been restrictedby the
physicalbarrierof the Coast Range mountainswith their extensiveice
fields.Access fromthe interiorregionshas for many species only been
possiblevia thelargerrivervalleysthatbisectthe Coast Range mountains.
However,access was notpossiblethroughall rivervalleys.The precipitous
barrier
canyonof the CopperRiver has apparentlyservedas an effective
in preventingmoose frompenetratingto the favourablehabitat of the
CopperRiverdelta.Moose were not presentin the Yakutat-DryBay area
until30-40yearsago,afterthe recessionof the glaciersthatobstructedthe
Alsek River valley near the Alaska-BritishColumbia boundary(Kindle
1952). Moose were apparentlynot presenton the lower Stikinein Alaska
whengold seekerstraveledthroughthe area in the mid-1870'sduringthe
Cassiar goldrush,but theyhad becomeestablishedthereshortlyafterthe
turnof the century(Swarth1922). A legendof the StikineIndiansof the
area tellsthatin thepasttheStikinevalleywas obstructed
by thecoalescing
of the Greatand Choquetteglaciersand thatthe riverat the timeflowed
througha tunnelbelow the ice (Kerr 1948). Great Glacier at the present
timeterminates
onlya fewhundredmetresfromthe river.
Thereis someevidencethatsmall,localizedrefugiaexistedin theQueen
CharlotteIslands (McCabe and Cowan 1945; Foster 1963), in the region
betweenCape Spencerand Katalla (Miller 1958), on the Kenai Peninsula
(Heusser 1960; Karlstrom1964), and on Kodiak Island (Karlstrom1957),
but mostofthesewere probablytoo smallto supportmammalpopulations
or,as in thecase oftheQueen CharlotteIslands,mayhave been too isolated
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10
POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
to serve as a pointfromwhichthe largerland mammalscould move into
areas.The smallerland mammalspresenta somewhatdifferent
surrounding
of the possiblelocationand extentof small refugia
picture.Consideration
in termsoftheevidenceofunglaciatedareas in the southerncoastalregion
is perhaps misleading,because the sea-level was much lower in lateWisconsintimesthanat presentand large areas thatare now coveredby
theoceanwouldhave been exposedor ice covered.Hultén (1937) considers
the currently
shelfas a possiblerouteof migration
submergedcontinental
ofplantsfromthe regionofWashington
and Oregonand the Queen CharlotteIslandsto southerncoastalAlaska immediately
afterglaciation.Both
Heusser (1960) and Hultén (1937) presentbotanicalevidencesuggesting
the existenceof a refugiumin the Kenai Peninsulaarea. On the basis of
geologicalevidence Karlstrom(1964) has reportedon the existenceof
Pleistocenerefugiaon the westernside of the Kenai Peninsula under
climaticconditionsnotgreatlydifferent
fromthoseof today.These refugia
could have been the source of some of the floralcomplexrepresentedby
pollen in the postglacialbog depositssampledby Heusser near Seward.
Heusser,however,suggestedthe existenceof a "local" refugiumlargely
on the basis of the earlypresenceof Sitka sprucein the Seward deposits,
and it is doubtfulwhetherSitka sprucecouldhave survivedunderclimatic
conditions
in thewesternKenai Peninsularefugia.Geologicalevidencefor
refugiain thePrinceWilliamSound area is lackingbut thereare extensive
coastalshelvesthatwouldbe exposedby a loweringofpresentsea-levelby
100metres.Fig. 1 is a map ofthesoutherncoastalregionofAlaska showing
the 100 and 200-metre
depthcontourswhichindicatethatappreciableland
areas wouldbe exposedby a loweringofthepresentsea-level.The postulation of refugiain low areas now submergedseems more logical than the
formsofplantsand smallmammalssurvivedon
postulatethatlow-altitude
thefewnunataksthatmayhave existedon some of the islands.That these
coastalshelfareas wereunglaciatedduringtheWisconsinglacialmaximum
is subjectto question.Glaciationin thelowlandsoftheKatalla-Yakutat-Dry
notmuchmoreextensivethanat present(Miller
Bay areas was apparently
1958). However,Karlstrom(1964) feels that on the basis of geological
evidencefromtheislandsofPrinceWilliamSound and frombottomsamples
fromthe coastal shelfit is probablethatmostareas in the adjacent Gulf
of Alaska whichwould be exposed by a loweringof sea-levelby 100 m.
were glaciatedduringthe Wisconsinglacial maximum.Johnston(1933)
has suggestedthatthe risingof land adjacentto the coast afterice started
to recedeprobablyprecededthe rise of sea-levelcaused by meltwater.If
anyrefugiadid existin areas now submerged,
speciesofplantsand animals
in
them
would
have
been
able
to
follow
the recedingice to the
existing
landnowabovesea-leveland thussurvivewhentherefugiabecameflooded.
Small Mammals
The presentdistribution
and affinities
ofsmallmammalsin theAlaskan
southerncoastal area can be explainedby eitheror both of the following
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POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
11
hypotheses:
1. Refugia existed in some offshoreareas now submergedat least
duringthe Wisconsinglaciation,as well as land connectionsbetween
islands or betweenislands and the mainland.
ofsomespeciesofsmallmammalsoccurringon widely
2. The affinities
separated islands are the result of parallel morphologicalchanges
stimuliin postglacialtimes.
occurringundersimilarenvironmental
faunal relationships
oftheregionare illustrated
Someoftheinter-island
discussion.MammaltaxonomyfollowsRausch (1953) and
in the following
Hall and Kelson (1959) and forthe purposesof thispaper Rausch is consideredthe finalauthority.
In the AlexanderArchipelagoendemicformsoccur most frequently
on theouterislands,includingChichagof
, Baranof, Coronation,
Warren,and
Forresterislandswhereasthe islands lyingcloser to the mainlandmore
of
oftenare occupiedby mainlandforms.This is shownby the distribution
of
P.
which
maniculatus
is
restricted
of
the
members
genus Peromyscus
tothemainlandand mostoftheadjacentislands,includingthelargerislands
oftheQueen Charlottegroup,whereasthe largerform,P. siikensis,occurs
on Baranof,Chichagof,Coronation,Warren,Duke, and Forresterislands
and in the Queen Charlottegrouponlyon Kunghit,Frederick,Hippa, and
a fewothersmallislands.Foster(1963) has recentlysuggestedthatP. manibecause a clineexistsbetweenthem,
culatusand P. siikensisare conspecific
differences
are notgreat,and theyprobablyinterbreed.
theirmorphological
distribution
The genus Microtusalso has a characteristic
patternin
the AlexanderArchipelago.M. longicaudusis presenton mostislandsand
the adjacentmainland.An endemicspecies,M. coronarius,closelyrelated
to M. longicaudus,is foundonly on Coronation,Warren,and Forrester
islandswhereason Baranofand ChichagofislandsM. oeconomusis present,
whichoccursalso on the nearestpartsof the mainlandin the vicinityof
GlacierBay.
Sorex obscuruslongicaudais the mainland
Amongthe insectivores,
formoccurringalso on a fewof the nearestislandsin the southernpart of
theregion.S. o. elassodonis presenton mostotherislandsofthe Alexander
ArchipelagoincludingBaranofand Forresterislandsand the largerQueen
CharlotteIslands,but S. o. malitiosusis foundonly on Coronationand
to KunghitIsland in the
is restricted
Warrenislandsand S.o. prevostensis
Charlotte
Queen
group.
betweenseveralof the outerislandsof the AlexThe faunalaffinities
ander Archipelagoand the Queen Charlottegroup,particularlyBaranof
and Warren-Forrester-Kunghit
and Chichagof-Coronation
(and othersmall
islandson the westernside of the Queen CharlotteIslands), suggestthat
theseareas had closerland connections
duringsomepastperiod.A lowering
associated
with
the Wisconsinperiodwould not
100
m.
of
the
sea-level
by
connection
between these island groups
land
a
continuous
about
bring
and
masses
would
be
the interveningchannels
the
land
larger
although
wouldbe fewerand narrower.It is possible,however,thatduringa slightly
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12
POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
earlierperiod,beforeCross Sound, ChathamStrait,SummerStrait,and
Dixon Entranceweredeepenedby glacialaction,landbridges
betweenthese
areas could have been exposed aftera loweringof the sea-level.Cowan
of the Peromyscussitkensisgroupand of
(1935) feelsthatthe distribution
Sorex obscuruselassodonsuggeststhattheseformssurvivedthe Wisconsin
glaciationon the outerislandsin thisregion.On the basis of his studiesin
the Queen CharlotteIslands,Foster (1963) suggeststhat the evidenceis
strongfortheexistenceofWisconsinrefugiatherebut feelsthatP. sitkensis
and possiblyS. obscuruselassodondid notsurvivetheWisconsinglaciation.
He postulatesinter-island
dispersaloftheP. sitkensisformsvia Indiancanoe
in Recenttimes.
Althoughmammalsconfinedto west-coastrefugiawould apparently
be in an advantageouspositionto occupyland areas exposedby thereceding
from
ice, theirpoorsuccessin thisrespectin contrastto formsoriginating
themainlandcouldbe explainedby thewide waterbarriersseparatingthe
westernmost
islandsfromthoseadjacentto themainlandand theapparently
pooreradaptabilityof the insular forms.It is generallyrecognizedthat
insular species frequentlybecome highlyspecialized and thereforeless
adaptablethan mainlandforms(Mayr 1942). Cowan (1935) pointedout
this suggestedrelationshipforPeromyscussitkensis,whichhe feltto be
a less "vigorous"species than P. maniculatus.Additionally,if the two
"species"interbreedas Foster (1963) suggeststhe muchlargergene pool
of the mainlandformwould enable it to absorbthe insularpopulationsto
whichit had access.
In thePrinceWilliamSound regionHinchinbrook
and Hawkinsislands
show the closest affinities
to the adjacent mainland,whereas Montague
Island has endemicmammalianformssuggestinglongerisolationand posto the Kenai Peninsulathanto adjacentHinchinsiblycloserrelationship
brookand HawkinsIslands.Hinchinbrook
Entrancehas apparentlybeen a
barrierto mammalianmovementduringpostglacialtimes.
fairlyeffective
Table 1. List of fossil mammalsfromNorth American Pleistocene refugia that have
been presentin Recent timesin the southerncoastal region of Alaska.
InteriorAlaska-Bering
Sea refugium1
Carnivora
Wolf
Black Bear
BrownBear
Artiodactyla
Deer
Moose
Elk
Caribou
Mountainsheep
Mountaingoat
Canissp.
Ursussp.
Alcessp.
Cervuscanadensis*
Rangifer
sp.
Ovisdalli
southofcontinental
ice sheet2
Refugium
Canislupus
Ursusamericanus{Euarctosamericanus)
Odocoileus
hemionus
Alcesalcesamericanus
{A. americanus)
Cervuscanadensis
Rangifer
sp.
Oviscanadensis(0. montana)
Oreamnos
sp.
1. Péwé, T. L. 1957. Permafrost
and its effecton lifein the North.18thBiol. Colloquium
Corvallis,Oregon,pp. 12-25.
2. Osborn,H. F. 1921.The age of mammals.New York: MacmillanCompany.635 pp.
3. Murie,O. J. 1951.The elk of NorthAmerica.Harrisburg,
Penn: StackpoleCo. 376 pp.
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POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
13
rutilushas reachedbothHawkinsand Hinchinbrook
islands
Clethrionomys
fromthe adjacentmainlandbut has failedto reach MontagueIsland. The
same situationapparentlyalso holds for the spruce grouse,Canachites
canadensis.Montague Island has two endemic subspecies of rodents,
Microtusoeconomuselymocetesand Marmota marmotasheldoni. The
marmotof the mainland,M. m. caligata is also presenton Hawkins and
Hinchinbrook
islands.While some of the MontagueIsland fauna exhibit
fromthoseofadjacentland masses,thesedifferences
differences
subspecific
apparentlyhave been the result of isolationfromrelated stocks during
postglacialtimes.
The mammaliancomplexof Kodiak Island, althoughsparse, shows
withthatof the Alaska Peninsula.Mammalspresentare
closestaffinities
formsand do not suggestlong isolation.
mainland
similar
to
very
Large mammals
All RecentlargelandmammalsofthesoutherncoastalregionofAlaska
are postglacialarrivalscomingfromrefugiaeitherin theinterior
apparently
ice sheet.Species
Sea regionor fromsouthofthecontinental
Alaska-Bering
thatwere presentin thesetwo refugiaduringPleistocenetimesand later
occupiedthe southerncoastal regionof Alaska are shownin Table 1. It
shouldbe understoodthat these lists are based on the findingsof fossil
remains,and theindicatedabsenceof an animalin one of the refugiais no
proofthatitdidnotoccurthere.However,thefairlyextensivefossilremains
of thesespecies
unearthedin bothareas probablyindicatethe distribution
2
distribution
of large
duringtheWisconsinperiod.Fig. showsthe present
mammalsin the southerncoastal regionof Alaska.
Brown bear, Ursus arctos
RemainsoftheUrsusarctostypehave been foundonlyin the Alaskan
Pleistocenematerialand are not knownfromregionssouth of the contiof the brownbear in Alaska suggests
nentalice sheet.Presentdistribution
from
a
northern
refugium(Swarth1936). The presenceofthe brown
origin
bear on all large islandsnorthwestof FrederickSound includingKodiak
Islandand theislandsofPrinceWilliamSound suggeststhatthisbear had
access to theseareas in a veryearlypostglacialperiod,possiblybeforethe
and priorto the arrivalof the black bear
sea-levelhad risensubstantially
and mostungulates.The presentlack of movementof brownbears across
the water channelsseparatingthese islands also supportsthe thesisthat
thesebears reachedthe islands when access was easier than at present.
Possiblyaccess to the northernislandsof the AlexanderArchipelagowas
via the coastal routefromthe Prince WilliamSound region.The type of
afterice recessionwould certainlyhave been
habitatexistingimmediately
favourableforbrownbears. Salmon,which are an importantcomponent
of the summerdiet,are knownto becomeestablishedin streamswithina
fewyearsafteraccess to the sea is possible,and the sedges,berry-bearing
ice recessionare
shrubs,and othervegetationfirstoccupyingland following
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14
POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
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POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
15
the preferred
vegetablefoodof thesebears. In this respecthabitatwould
be favourablemuchearlierforbears than formostungulates.
The failureof the brownbear to occupyislands south of Frederick
Sound when access became available may be a resultof prioroccupancy
by theblackbear.A previouslyestablishedspeciesobviouslyhas an advanto occupythesame ecologicalniche.In
tageovera similarformattempting
recenttimesbrownbears occasionallyreach Mitkofand Wrangellislands
movement
but have not been able to establishpopulations.Additionally,
ofbrownbearssouthalongthemainlandfromLynnCanal to Cape Fanshaw
duringearlypostglacialtimesby extensiveareas
mayhave been obstructed
ofslowlyrecedingglaciers,manyofwhichevennowreachthesea, and later
movementof land mammals.
by thegeneralrise in sea-levelthatrestricted
Black bear, Ursus americanus
The black bear is apparentlya migrantfromthe south.There is no
evidencethatit was presentin the northernrefugium.
Althoughthe black
bear is widelydistributedon the Alaska mainlandit is absent fromthe
of FrederickSound,suggesting
thatit arrivedin
coastalislandsnorthwest
the adjacentmainlandareas later than the brownbear and consequently
to theseislandsas was the brownbear.
was not successfulin penetrating
here to notethatthe black bear is todayassociated
It is perhapspertinent
withforestedareas,whereasthebrownbear appearsmoreadaptable,being
The black
foundin thetreelesstundra,as well as in the coastalrainforests.
bear is not presenton the Alaska Peninsulaor the treelesscoastal areas
adjacentto theBeringSea and ArcticOcean.
South of FrederickSound the black bear has occupiedall the larger
islands of the AlexanderArchipelagoand is also found on the Queen
CharlotteIslands.Again it appears to have reachedthese areas fromthe
southpriorto thearrivalofthebrownbear fromthenorthwest.
Its presence
on the Queen CharlotteIslands indicatesa fairlyearly arrival,according
to Osgood (1901),as theseislandsare now separatedfromthe mainlandby
the35-mile-wide
Hecate Strait.McCabe and Cowan (1945) suggestthatthe
blackbear mayhave survivedthelast glaciationtogether
withseveralother
on theseislands.The Queen CharlotteIsland black
mammalsin a refugium
subbear,recognizedas a distinctspeciesformanyyears,is now afforded
specificstatus(U. a. charlottaeOsgood). Access to the islandsof the AlexanderArchipelagosouthofFrederickSound poses no seriousproblemsfor
moderateswimmers,
as waterchannelsbetweenislandsand the mainland
are frequently
less thana milewide.
Wolf,Canis lupus
In thesoutherncoastalregionofAlaska the distribution
patternof the
wolfis almostidenticalwiththatof the black bear,but thisapparentlyis
is the absence
nota resultofsimilarzoogeographical
history.A dissimilarity
ofthewolffromthe Queen CharlotteIslands.The distribution
of the wolf,
of a
an obligatepredator,obviouslydepends on the prior establishment
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16
POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
suitablepreyspecies.In the taiga and arcticregionsof NorthAmericathe
main prey of the wolfappear to be membersof the Cervidae.Although
mountainsheep,mountaingoats,bison,and musk ox fall prey to wolves,
basis to maintainthe wolf
thesespeciesdo not appear to offera sufficient
as a speciesin any givenarea. Murie's (1944) studiesof wolves in Mount
McKinleyNationalPark,wherebothmountainsheepand caribouare available,tendto supportthisassumption.
Alaska
The wolfprobablyfollowedthe deer into coastal southeastern
and penetratedto thosedeer-occupiedislandsto whichtheywere capable
ofswimming.
Baranof, and Chichagofislands
TheirabsencefromAdmiralty,
and the Queen CharlotteIslands (althoughin recenttimesthe onlynative
cervidon the Queen CharlotteIslands,the caribou,may have existedat
toolow a densityto supportthewolf)suggeststhatthe wolfarrivedin this
wereprobablynottoo different
regionat a fairlylate date,whenconditions
fromthoseat present.The absenceof the wolffromthe islandsof Prince
WilliamSound and Kodiak Island is understandable
because ungulatesare
not nativeto these islands.In the mainlandregionfromPrince William
SoundtoCape Spencer,wherethemountaingoatis theonlynativeungulate,
withthe exceptionof the recentlyarrivingmoosein the Yakutat-DryBay
area, wolvesare presentonlysporadically,
apparentlybecause individuals
occasionallypenetratethe Coast Range mountains.
Black-taileddeer, Odocoileushemionussitkensis
The black-taileddeer came obviouslyfromthe south,the speciesbeing
Its successpresentduringPleistocenetimeonlyin the southernrefugium.
in the AlexanderArchipelagodependedon a suitable
ful establishment
habitatwitha vegetationprobablynot unlikethe presentone. This would
untila suitablehabitathad developed
precludeitsdispersalfroma refugium
notonlyin theAlexanderArchipelagobut in theintervening
areas as well.
This factor,combinedwiththe deer's apparentlyfollowingthe highlydissected coast and offshore
islands,undoubtedlyslowed its northwestward
In addition,
on themainland,wheredeepwintersnows
movement.
conditions
are common,
are notnearlyso favourablefordeeras on theadjacentislands,
and the establishment
of deer along the coast would be delayed in those
areas wheretheislandsare separatedfromone anotherby widewaterchannels. The absenceof deer,exceptthroughrecentintroduction
by man,on
the Queen CharlotteIslands atteststo the effectiveness
of Hecate Strait
as a barrierto thesequite strongswimmers.
Deer have occupiedall islands
oftheAlexanderArchipelagocapable of supporting
them(withthe exceptionof ForresterIsland) and occur on the mainlandnorthwestof Juneau
in the Eagle River area. Their access to a favourablehabitatin Prince
WilliamSound and on Kodiak Island has been blocked by the exposed
coastalarea northofCrossSoundwhereconditions
are notsuitablefortheir
survival.In recentyearsdeer have been successfully
introducedby man to
islandsin YakutatBay,theislandsand adjacentmainlandofPrinceWilliam
to note thatdeer have been
Sound,and to Kodiak Island. It is interesting
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POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
17
able to reachAdmiralty,
Baranof, and ChichagofIslandswhichare isolated
by fairlywide water channels,whereastheirpredator,the wolf,has not
been able to penetrateto theseislands.
Moose, Alces alces
The moose,althoughapparentlypresenton the Kenai Peninsulasince
earliestrecordedtimes(Lutz 1960),has onlyrecentlypenetratedthe Coast
Range mountainsat the Alsek (Yakutat-DryBay area), Chilkat,Taku,
Stikine,and Unuk River valleys. Extensiveoccupationof the southern
coastal regionsof Alaska by moose cannotbe expected,because suitable
habitatsare restricted
to a fewsizableareas wherethe vegetationis stillin
theearlystagesofsuccessionand whichoccuronlyin thelargerrivervalleys
ofthemainlandand on theterminalmorainesof glaciersthathave receded
introducedin the past 15 years to
recently.Moose have been successfully
theCopperRiverdeltaand BernersBay.
Mooseexistedin thePleistocenefaunaofboththenorthern
and southern refugiaand presentdistribution
seems to indicatethat the formA.
alces gigas derivedfromthe northernrefugiumwhereas the otherthree
North Americanraces were of southernorigin.A. a. gigas is present
whereverthe moose occursin the Alaskan coastal area fromthe Alaska
Peninsulasoutheastto the Taku River althoughintergradation
withA. a.
andersoniprobablytakesplace in the vicinityof the Taku River.Moose in
the Stikine and Unuk River valleys are more typicallyof the smaller
andersonitype,whichoccurs in adjacent BritishColumbia.It should be
notedthatthis line of demarcationbetweenraces of moose roughlycorrespondsto thatbetweenthe brownand black bear on the islandsand in
bothcases resultsfromthe meetingof formsapparentlyderivedfromdifferentrefugia.
tarandus
Caribou,Rangifer
Caribouhave notpenetratedintothesoutherncoastalregionofAlaska
excepton theAlaska Peninsulaand the Kenai Peninsulaand on bothhave
been restrictedalmostexclusivelyto the dryerwesternsides. In the remainderof the regionsuitablecaribouhabitatdoes not exist. The small
numbersofcariboupresenton GrahamIslandoftheQueen Charlottegroup
untilabout1920 (Cowan and Guiguet1956), apparentlywere a relictfrom
a periodwhenthevegetation
was morefavourableforthespecies.Changing
habitat,possiblyacceleratedby firesstartedby man,may have caused the
extinction
ofthe caribouon the Kenai Peninsulabefore1900.
Elk, Cervus canadensisroosevelti
The RecentspeciesofNorthAmericanelk or wapitihas been reported
fromboththesouthernand northern
refugia.It apparentlybecame extinct
in Alaska sometimeduringthe late Pleistoceneand has failedto returnto
Alaska in post-glacialtimes.The RockyMountainelk (C. c. nelson) has
been introducedby man to the Queen CharlotteIslands and the Roosevelt
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18
POSTGLACIALDISTRIBUTIONPATTERNSOF MAMMALS
elk (C. c. roosevelti) to AfognakIsland in the Kodiak group. The elk possibly
would be successful in other coastal areas, although the Queen Charlotte
elk have apparently remained in a very restrictedarea on Graham Island
with a stabilized population of a few hundred animals (Foster 1961). The
failure of the elk to reach Alaska in Recent times is apparently caused by
the extensive interveningareas of unfavourable habitat. The Roosevelt elk,
the race best adapted to the wet coastal forestregions, occurs naturally as
far northas Vancouver Island and formerlywas found on the mainland as
far north as the Fraser River delta. In many respects its winter diet of
broadleaf species closely resembles that of the moose, thereforethe absence
of the elk fromthe coniferousrain forestsof the coast north of the Fraser
River is understandable.
Mountain goat, Oreamnos americanus kennedyi
The mountain goat is known only fromthe southern refugiumand has
apparentlyextended its range since the Pleistocene northwestwardthrough
the Coast Range mountainsof the mainland to the Kenai Peninsula and the
Talkeetna Mountains. Because the mountain goat lives in the alpine zone
during the summer and the coniferousforestduring the winter,the coastal
mountainshave been a help to spreading rather than a barrier as they are
to many other mammals. On the other hand, the goat's preference for a
mountainous habitat has contributedto its failure to cross to the larger
islands adjacent to the coast,where it would undoubtedlyfindsupport.While
not as proficientswimmersas deer, goats are capable of crossingthe narrow
channels separating many of the offshoreislands fromthe mainland. Thus,
goats have reached Culross and Bainbridge islands in Prince William Sound
(Klein 1953) ; one goat was observed on Wrangell Island for several years
and they apparently occur on Pitt Island just south of Prince Rupert
(McCabe and Cowan 1945). All these islands are separated by narrow
straitsfromthe mainland,which rises precipitouslyfromthe sea. The successfulestablishmentof goats on any of the islands would require more than
just the occasional crossing by a single goat. Goats have been introduced
by man to Baranof, Chichagof,and Kodiak islands.
The present northernand western limits of mountain goat distribution
may be a productof a relativelylate arrival froma rather distant refugium.
There are indicationsthat the mountain goat is extending its range northward and therehave been occasional reportsin recentyears fromthe eastern
portion of Mt. McKinley National Park in the Alaska Range (Klein 1953;
Murie 1962). The low broad Susitna River valley has probably been a barrier to the movementof goats west fromthe Chugach and Talkeetna Mountains and may account for their absence fromthe west side of Cook Inlet.
Precipitous forested slopes broken by rock outcrops appear to be an
importantcomponentof mountain goat winter range in areas where heavy
snows are common. Such areas shed the snow to a large extent and offer
cover and access to food. This factormay be of importancein determining
the long termsuccess of mountain goats on Kodiak Island where they have
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POSTGLACIAL DISTRIBUTION PATTERNS OF MAMMALS
19
or in futurerangeextensionseitherby naturalor artificial
been introduced
means.
Mountainsheep,Ovis dalli
Mountainsheepwere partof the Pleistocenefauna of boththe northernand southernrefugia;thethinhorn
sheep (O. dalli) was the formofthe
Alaskanrefugium,
and thebighornsheep (O. canadensis)thatofthe southernrefugium.
O. dalli is the speciesoccurringnow in Alaska and southto
northernBritishColumbia,and the bighornsheep occupies the Rocky
Mountainsnorthto centralBritishColumbiaand Alberta.Mountainsheep,
the entireyear,requirea relativelydry
beingprimarily
grazersthroughout
habitatwheregrassesand otheralpine vegetationare available to themin
thesesheep have not been able to
bothwinterand summer.Consequently,
on the coastal side of the
of
the
areas
into
heavy precipitation
penetrate
This is borneout by mountainsheep livingon the
Coast Rangemountains.
dryinteriorslope of these mountainsand thereforehavingaccess to the
coastalareas. The mountainsheep does occur on the Kenai Peninsulabut
hereit is restricted
to thedrywesternslopesof the Kenai Mountains.
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