REPTILES
22
s. (1936): The jaw-tag method of marking
fish. Pap. Mich. Acad. Sci. Art Lett. 21: 651453.
STBBBT, J. s. (1970):Alligator Research Project. Biennial
report. Mimeograph. School of Forestry, Univ. of
Gainesville, Florida.
TINKLB, D. w. (1957):Ecology, maturation and reproduction of Thamnophis sartrihts proximus. Ecology 38:
SHBTTBR, D.
69-77.
WBARY, G. c. (1969):A n improved method of marking
snakes. Copeia 1969: 854-855.
WOODBURY, A. M. (1948) : Studies of the desert tortoise,
Copherus agassirii. Ed. Monogr. 18: 145-200.
WOODBURY, A. M. (1951):
A snake den in Tooele County,
Utah. Syntp. Herpet. 7: 1-52.
WOODBURY, A. M. (1933): Methods of field study in
reptiles. Herpetologica 9: 87-92.
V ~ T BB.L(1976):
,
Die Amphibien Rheinhessens unter
besonderer Beriicksichtigung der Umgebung von
Oppenheim. Main%.Naturw. Arch. IS: 183-221.
Manuscript submitted 13 March 1978
Notes on reproductive patterns of reptiles in
relation to captive breeding
JOZSEF LASZLO
Supervisor, Reptile Department, San Antonio Zoological Gardens, San Antonio, Texas 78212, USA
At least three main types of reproductive pattern
can be recognised in reptiles, each with a number
of subtypes. The main groupings, designated
according to the breeding seasons (St Girons &
Pfeffer, 1971), are: (I) spring and early summer
breeders; (2) autumn (fall) and winter breeders;
(3) animals whose breeding cycles are apparently
unrelated to seasonal stimuli.
PATTERN I -SPRING
A N D EARLY SUMMER
BREEDING
Among the spring and early summer breeding
group there are two further subdivisions. Type A
reptiles are affected primarily by the change from
cold/dark to warm/light conditions (posthibemation). This is the critical factor which
induces mating behaviour, either immediately or
within eight to ten weeks after emergence from
hibernation, usually regardless of whether daylengths are extended beyond IZ hours (Licht,
1972a, 197zb; Aleksiuk & Gregory, 1974;
Aldridge, 197s; Aleksiuk & Hawley, 1976).
In contrast, the type B reptiles, mainly those
living in temperate and subtropical zones, can be
thought of as the long day/short night species and
respond when daylengths are extended to 14-16
hours, the optimum light : dark ratio being 2 : I.
In some cases, they can be induced to mate by
increased daylength alone with no prior exposure
to a cool dark period (Licht, 1969; Laszlo, 1975,
1977a; Wagner & Slemmer, 1976). For example,
a I6-hour day, over a two month period, has
proved sufficient to induce mating in most species
of Elaphe and Lampropeltis, in eublepharine
geckos and some others but in most other reptiles
studied some form of temperature change
appears to be the triggering factor. The majority
of tropical species cannot usually be stimulated to
mate merely by changing the photoperiod since
in the seasonal tropics (lat. 10-23p N and S) the
annual variation in daylength is only 104-134
hours (Bartholomew, 1959; Lofts, 1970).
The temperature change necessary to stimulate
breeding depends on the reproductive pattern
involved. In the case of the type B, long day/short
night species, the project can begin with a I 3-hour
day in the first week, increasing half-an-hour
each week until a 16-hour day is reached and
maintained for the remainder of the eight- to
ten-week period. We recommend full spectrum
fluorescent light sources (Ott, 1965; Thorington
et al., 1965; Laszlo, 1969; Wurtman & Weisel,
1969; Wurtman, 1975) with high colour correction and a chromatic index number of at least
88-91CRI. Vita-Lite was the choice of the reptile
department at the San Antonio Zoo (Laszlo,
1969). Incandescent lamps of this type are
Superwhite reflector plant lights and Fluomeric
(HID) high intensity mercury vapour discharge
bulbs, Deluxe White. Both are highly colourcorrected (but without the UV band) with a
chromatic index number of 88 and are available
23
RBPTILBS
in different wattages. In contrast to many other
types of lamps, all the above are balanced to
resemble the solar or visible spectrum and are
rich in the red band region.
Our snakes are kept under low light levels
(10-40 foot candles) throughout the year, except
during breeding periods when higher intensities
are used. Extended low light levelsalsoworkwell.
However, so that light and dark are sharply
defined, we chose high intensity lamps of several
hundred f.c. (16 lamps 212 W 96 inch TH17
UHO 15ooMA power twist). The lamps are
equipped with individual switches to permit
fmer control of light intensity and the quantity of
heat produced. To keep the temperature within
the desired limits some type of air-conditioning
is necessary, especially for species with a low
optimum temperature and high moisture requirement, such as some high mountain forms, for
example subspecies of Crotalus willardi and C.
polystictus. In these cases, lower light levels,
which generate less heat, are recommended to
prevent dehydration.
Exposure to cool, dark conditions (bbernation) followed by a period of warmth and light
induces mating in many temperate and subtropical reptiles, as well as in some tropical species.
The timing of spermatogenesisand enlargement
of the gonads is the other major variation in type
found in the Pattern I spring/summer breeding
reptiles. In animals with 'prenuptial spermatogenesis' (Volsere, 1944; Lofts et a]., 1966) sperm
development begins in early spring and is
followed by mating in spring or early summer.
In the northern hemisphere most species actually
mate from February to mid-June, with a peak
period in April and May in temperate and subtropical climates (Bullough, 1961). For seasonal
tropical species spring mating occurs from the
end of February throughout March, following
the coldest part of the dry season (Nedl, 1962;
Shine, 1977a). In the southern hemisphere, spring
mating of tropical reptiles takes place from the
end of August throughout September. In general,
the closer to the equator the earlier breeding
commences (Bullough, 1961). In the second type,
'postnuptial spermatogenesis (Volsne, 1944; St
Girons, 1957, 1966; Goldberg & Parker, 1975;
Shine, 1977a, 1g77b) occurs in late summer and
early autumn, usually from mid-August throughout October, and the sperm is stored in the
epididymis and ductus deferens over the winter
until breeding takes place the following spring
and early summer.
PATTERN 2 - A U T U M N
A N D WINTER
BREEDING
These reptiles are also affected by a change in
environmental conditions. However, in this case,
it is the change from warm/light conditions of
prehibernation to cool/dark conditions which
triggers mating behaviour. For most short day/
long night true winter breeders the optimum
dark : light ratio is z : I . It can vary, however,
to complete darkness (Wall, 1921; Shaw et al.,
1939; Minton, 1966; Myres &Bells, 1968; Fitch,
1970; Wagner et af., 1976; Laszlo, 1977a; Ross &
Larman, 1977).
With such animals there are two approaches to
captive breedmg. The first method uses a photoperiod of an 8-hour dayl16-hour night with day
temperatures of 25-26"c (i.e. under the feeding
optimum of 27%). For most boas and pythons
night temperatures should not exceed 21012 and
with Sanzinia spp and Python regius they should
drop to a minimum of 18'c (Laszlo, 1975,1977a).
The subtropical subspecies of Drymarchon and
Heloderma need night temperatures of 14-16"c.
Alternatively the reptiles can be kept uniformly
cool and in complete darkness. Tropical species
should be maintained at 18-21Oc and subtropical
species at 14-16%. This appears to be as effective
in stimulating breeding but is not considered as
safe as the first method since in natural conditions
winter basking is known to occur (Myres &
Eells, 1968).
In nature, short daylengthsare alwaysassociated
with simultaneous lowering of temperature and
hibernation but in captivity, successful mating
can result without any sigtllfcant temperature
change although it will still occur only during the
normal breedmg season (Bullough, 1961).
Winter breeding subtropical reptiles mate at
temperatures of 16"c and above in nature. In
tropical climates, mating takes place at 18-21Oc,
usually during the coldest part of the dry season
in December, January and February (northern
hemisphere) (Wall, 1921) and June, July and
August (southern hemisphere). In the Bahaman
Epicrates it is known as late as early April (Laszlo,
19772).
24
REPTILES
Spring and summer breeders
Type A - affected primarily by temperature change
from cold/dark to warm/light (light : dark
ratio c. I :I)
Thamnophis sirtalis parietalis
Crotalus (most North American, including Mexican, species except C. durissus ssp)
Vipera (most spp)
Type B - affected primarily by daylength alone
(long daylshort night) (light : dark ratio
c. 2 : I)
Elaphe guftata ssp
Elaphe obsoleta ssp
Elaphe subocularis
Lampropeltis getulus ssp
Lampropeltis hiangulum polyzona
L. t . nclsoni
L. t. sinabae and other ssp
Lampropeltis mexicana ssp
Eublepharis macularius
Hemitheronyx cuudicinctus
Coleorryx spp
PATTERN I
Winter breeders - affected primarily by
temperature change from warm/light to
cold/dark (or short daylengths) (light : dark
ratio c. I : 2)
Boinae (niost if not all species)
Pythoninae (most if not all species)
Drymarchon corais ssp
Heloderma horridum ssp
H. suspecturn ssp
Crotalus durissus ssp (N American and possibly
S American)
C. vegrandis
C. unicolor
C. lepidus ssp (Autumn)
C. willardi ssp (Autumn)
Agkistrodon bilineatus ssp (Autumn)
Vipera aspis ssp (Spring and Autumn)
while in temperate and subtropical climates
autumn mating extends from mid-August
throughout September (Goldberg & Parker,
1975). In some cases, especially with tropical
species, they are difficult to separate from the true
winter breeders because the breeding cycles
overlap. Nevertheless, it should be emphasised
that reptiles which mate in the autumn do diffcr
markedly from true winter breeders. Although
some species are also distinct fromspring breeders,
a number of reptiles usually designated as 'spring
breeding' mate at both seasons (St Girons, 1957).
Hence it is possible that autumn breeders may
actually have a closer relationship with spring
than with winter b r e e b g species. So although
decreasing daylengths and lower temperatures
may be the main influencing factors, further
investigation of autumn breeding reptiles is
needed.
PATTERN z
3 -INDEPENDENT BREEDING
In some reptiles ovulation occurs within the same
period each year independently of any outside
stimuli. To avoid interference with endogenous
rhythms, reptiles in general, and these animals in
particular, should be given the conditions necessary for mating at the time when the wild
population from whch they derive is known to
mate (Laszlo, 1977a). The strength of the internal
rhythm, however, varies depending on the species
(Bullough, 1961).
PATTERN
L E N G T H OF H I B E R N A T I O N A N D
TEMPERATURES
Independent breeders
Crmlus atrox
Lampropeltis getulur yumensis
PATTERN 3
Table I. Species showing the various types of
reproductive patterns as described in text.
Some equatorial lowland rainforest reptiles
(lat. IO"N-IO"S)reproduce throughout the year
(Bullough, 1961; Fitch, 1970). As with the
seasonal tropical breeders, equatorial boa and
python species seem to be affected primarily
by lowered temperature (Wall, 1921; Ross &
Larman, 1977) and little, if any, by daylength
changes.
Autumn breeders are less easy to define. In the
northern hemisphcre, the tropical autumn breeders will mate usually no later than December,
The annual disruption of the life cycle by lower
temperatures is most evident in temperate
climates but it also exists. if less obviously, in
equatorial lowland rainforest conditions. The
annual occurrence of a change in temperature is
necessary for reproduction in the majority of
reptiles.
The duration and temperature of hibernation
is critical. Apparently, important physiological
changes occur during the 'conditioning' period
(Aronson, 1965;Aleksiuk & Gregory, 1974) and
experiments have shown that it is essential to
hibernate captive reptiles for slightly more than
halfthe total natural hibernation period for good
breeding results. In general three months, or a
little longer, is sufficient for most, if not all,
reptile species.
BBPTILBS
We have successfully induced hibernation using
a converted soft drink cooler equipped with a
Ranco OIC-1410 refrigeration thermostat with a
temperature range of -4-z4"c (Laszlo, 1975,
19774.
Temperate climate reptiles: In the wild hibernation
usually lasts five to six months but in the extremely
cold northern margin it can last up to seven
months or more (Aleksiuk & Gregory, 1974).
Minimum recommended hibernation time in
captivity is slightly over three to three-and-a-half
months at 4-7"c.
ZS
minimum may be sufficient to induce mating in
captivity.
Generally cooler night temperatures occur for
an average of one to three months (eg. July,
August and September in the Galapagos (Lack,
1950)). In captivity, a minimum cooling period of
slightly over six weeks is recommended to
stimulate breeding. The minimum safe temperature limit for all lowland tropical reptiles
(including equatorial species) is 18"c although,
for short periods, they can withstand a drop to
14"c.
M I S C E L L A N E O U S H U S B A N D R Y TECHNIQUES
Subtropical reptiles: Winter isothermal lines are a
better guide to defining subtropical habitats than
latitude. In this text, reptiles distributed mainly
between 7-18"c January (N)/July ( S ) isotherms
(at sea level) are considered subtropical. Their
total natural hibernation is four to five months
and the minimum recommended captive hibernation is slightly over two-and-a-half months at
IC-13"c with the lowest limit at 7"c (Landsberg,
1969; White & Lasiewsky, 1971; Laszlo,
19774.
Seasonal tropical climate reptiles: These are inhabitants of areas which have a single rainfall maximum in the summer and a winter dry season
with recognisable temperature differences (Baker,
1g47a, 1947b; Neill, 1962; Shine, 1g77a). The
cooler temperatures usually last for a period of
three months, though it may vary from two to
four (Harrison-Church et al., 1967). In captivity
the minimum hibernation time is a little over two
months. Temperature should be maintained at
18-21Oc dependmg on whether the species is a
lowland cool form or a lowland warm form
(Laszlo, 1977a, 1977b).
Equatorial tropical c h u t e reptiles: Near the equator
the average annual temperature seldom ranges
more than 2 . 7 " ~and the diurnal variation is
normally no more than 8.3 'c. In some rainforest
habitats, the cool period is so slight and so brief
that it is oftenignored or overlookedby observers.
Yet despite the small seasonal changes, the
breeding periods are sharply defined (Lack, 1950;
Marshall & Hook, 1960; Bullough, 1961; Bourn,
1977) for most equatorial reptiles and temperatures 4"c less than the normal year round daily
Hibernating individuals should be kept slightly
moist to prevent dehydration and smaller species
need to be sprayed (especially around the cloaca)
once or twice weekly (Laszlo, 1977a). However,
this must be done with care as too much moisture
can cause pneumonia. Also, less moisture is
necessary for desert reptiles than for those from
woodland habitats. For the larger species,
drinking water should also be provided.
Dehydration is also a major risk when the
animals are removed from hbernation and
warmed to normal activity temperatures, and
they should be soaked in shallow lukewarm water
for several hours. To avoid sudden shock, both
the cooling and subsequent warming processes
must be done very gradually, in several stages if
necessary. Our own experiments have shown
that reptiles kept at temperatures with a normal
daily fluctuation have a greater survival rate
during hibernation than those kept at a constant
temperature throughout the year.
To maintain the proper fat cycles, individuals
should be fed more heavily in the summer, and
only lightly, if at all, in the winter. Lipid levels
are critical for hibemating and reproducing
reptiles, and in most snakes an inability to restore
lipid levels within a given time may result in
biennial (or even less frequent) reproduction (St
Girons, 1957; Tinkle, 1962; Wharton, 1966;
Derickson, 1976). In captivity, all hibernating
individuals should be in excellent health, slightly
fat, and free of parasites. The stomach should
contain no food just prior to and during
hibemation.
Vitamin D, appears to be an essential dietary
supplement for successful reproduction in captivity (Laszlo, 1977a). Activated vitamin D, can
26
be given throughout the year (except during
hbernation) in the form of Linatone, rubbed on
the food animal. Adult snakes receive one drop of
Linatone every two to three weeks and young
snakes one drop per week. The dosage is extremely important, as too much can cause
curvature and malformation of the bones.
c o d liver oil-calcium emulsion can also be
used as a source of vitamin D, (Wagner &
Slemmer, 1976). Calcium and phosphorus should
be given in a ratio of c. 2 : I (Simkiss, 1967;
Jenkins & Simkm, 1968; Laszlo, 1977a). Vitamins
A and E also appear to be important for reproduction and general health.
In the wild mating activity and food intake are
inversely related (Aleksiuk & Gregory, 1974) and
many reptiles do not feed during the mating
period. This does not always hold for captive
mating conditions and some animals will accept
food ifit is offered. Nevertheless, as high temperatures should be avoided to prevent sterilisation of
the germ cells (Cowles & Burleson, 1945), the
general temperatures should be maintained
at slightly under the optimum feeding
conditions.
One of the best and most efficient methods of
inducing mating is to house the sexes separately
throughout most of the year and introduce the 9
to the 6 only during the breeding season. A
breeding colony should have a minimum of
three pairs of any one species and ideally a
greaternumber o f 8 8 than ?? (Shaw et af., 1939).
Repeated separation and reintroduction on a daily,
weekly, or monthly basis helps to stimulate
interest during the breeding season.
Male snakes seem to be especially stimulated
by olfactory cues immediately after the ? sheds
her skin (Davis, 1936; Fukada, 1959; Crews,
1976); even the discarded shed from a 9, moistened and rubbed on her back, has occasionally
induced mating.
Gravid oviparous 99 should be given a box
containing nesting material (e.g. moist sphagnum
moss) prior to oviposition.
Reproductive maturity is determined by the
rate of development rather than age (Laszlo,
1977a). In nature, this condition is not usually
reached until three to five years of age. In
captivity, however, given quick growth, successful mating can occur as early as eight months old
(Wagner & Slemmer, 1976).
REPTILES
Using hibernation and photobiology, combined with well planned management and
techniques, many species of reptile can be reproduced in captivity not by chance but by definite
choice.
ACKNOWLEDGEMENTS
The author wishes to express his gratitude to Jerry
Benefield for preparing the manuscript, to Alan Kardon
for securing references and to Lionel Landry, Jr for
helpful suggestions in this study.
PR OD U C TS M E N T I O N E D I N T H E T E X T
Pluomeric and Superwhite: incandescent lamps
manufactured by Duro-Test Corporation, North
Bergen, New Jersey 07047,USA.
Liatone: activated vitamin D3 supplenient manufactured by Lambert-Kay, Division of Carter-Wallace
Itic, Cranberry, New Jersey 08512, USA.
Ranco 010-1410 refrigeration thermostat: nianufactured by Ranco Itic, Colunibus, Ohio, USA.
Vita-Lite: fluorescent tubes manufactured by DuroTest Corporation.
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