Recommendations for the Care of Amphibians and Reptiles in Academic Institutions
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Recommendations for the
Care of Amphibians and Reptiles
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in Academic Institutions
F. Harvey Pough
NATIONAL ACADEMY PRESS
Washington, D.C. 1991
Volume 33, Number 4 Fall 1991 S1Downloaded from https://academic.oup.com/ilarjournal/article-abstract/33/4/S1/744425 by Serials Biomed Library 0699 user on 03 January 2019
ILAR News
viridis).
On the cover: The green tree python (Chondropython
(Photo courtesy of F. Harvey Pough).
S2CONTENTS
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Introduction S5
Amphibians and reptiles in research and teaching S5
The biology of amphibians and reptiles S6
Distinctive characteristics S6
Sources of information S7
General recommendations for the care of ectothermal vertebrates S8
The physical environment S8
The biological environment Sll
Marking individuals S15
Breeding S15
Environmental conditions and medical care S16
Health precautions for release of animals S17
Health precautions for animal caretakers S17
Summary S18
Acknowledgements S18
References S18
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Recommendations for the Care
of Amphibians and Reptiles
in Academic Institutions
F. Harvey Pough, Ph.D.
Downloaded from https://academic.oup.com/ilarjournal/article-abstract/33/4/S1/744425 by Serials Biomed Library 0699 user on 03 January 2019
INTRODUCTION being studied. Studies of amphibians and reptiles often
have different perspectives and goals than those using
Amphibians and reptiles differ in many respects from traditional biomedical species. These differences are
the mammals and birds most commonly used in biomedi- reflected in the housing and care that is appropriate for
cal research. These differences affect the physical and the animals. In addition, the physical and biological
biological requirements of amphibians and reptiles in needs of amphibians and reptiles differ from those of
captivity. In this contribution, some basic biological char- mammals and birds, and are often more difficult to pro-
acteristics of these animals are described that are rele- vide in an artificial setting. Both of these factors must be
vant to their husbandry. My goal is to help members of appreciated by investigators working with these animals,
institutional animal care and use committees appreciate and by the individuals responsible for evaluating proto-
the requirements of amphibians and reptiles in captivity, cols and husbandry practices.
and to make suggestions that will be helpful in designing
housing and providing day-to-day care.
I will focus on amphibians and reptiles used for re- The Context of Study
search and teaching in colleges and universities. In the
sense that amphibians and reptiles are exotic animals in Many studies of amphibians and reptiles have an organismal
a biomedical context, there are parallels between their perspective. That is, the focus of study is the intact
use in academic settings and in zoos and aquariums. animal and the context is the species as it functions in its
However, the facilities and resources available at col- natural environment. This approach differs from the
leges and universities are more limited than those of traditional biomedical use of mammals and birds to illus-
most zoos and aquariums. These recommendations ad- trate general biological phenomena or to serve as models
dress the limitations and opportunities of small-scale of specific human diseases or genetic defects. In organismal
husbandry. research, behavior, ecology, physiology, and morphol-
The husbandry practices suggested here are compat- ogy are studied in the context of phylogenetic relation-
ible with the Health Extension Act (PL-99-158), with the ships and environmental specializations. Husbandry must
National Research Council's Guide for the Care and Use consider the entire biology of an organism so that normal
of Laboratory Animals (NRC, 1985) with the Canadian behavior, physiological response, and morphogenesis can
Council on Animal Care's Guide to the Care and Use of be assured. Much research in organismal biology is cur-
Experimental Animals (Canadian Council on Animal Care, rently directed to comparative studies that investigate the
1980) and with the Guidelines for Use of Live Amphib- evolution of physiological, morphological, and behav-
ians and Reptiles in Field Research (American Society ioral characteristics by studying a series of species (see
of Ichthyologists and Herpetologists et al., 1987). Brooks and McLennan, 1991; Harvey and Pagel, 1991;
and Huey, 1987 for examples of this approach). Studies
of this sort rely upon measuring the same phenomenon
(e.g., thermoregulation, parental care, or feeding me-
chanics) in several species. Reviewers of protocols must
AMPHIBIANS AND REPTILES IN understand that the study of multiple species of known
RESEARCH AND TEACHING phylogenetic relationship is an essential element of the
comparative approach, and is not unnecessary duplica-
Understanding the husbandry requirements of amphib-
tion.
ians and reptiles begins with understanding why these
animals, rather than traditional biomedical species, are
Practical Considerations
Dr. Pough is professor of Ecology and Systematics and director Providing environments suitable for amphibians and rep-
of the Laboratory of Functional Ecology at Cornell University tiles can be difficult. Domestic animals used in biomedi-
in Ithaca, New York. cal research have been bred to prosper under conditions
Volume 33, Number 4 Fall 1991 S5that can easily be maintained in an animal room. Am- and Jones (1987), and Pough et al. (1989) and the refer-
phibians and reptiles, on the other hand, are wild ani- ences therein.
mals, and the husbandry methods applied to them must
take this into account. Housing, food, and care must
match the physical and behavioral needs of each species. Distinctive Characteristics
Carefully designed physical and biological environments
are often needed, especially when the goal of husbandry Two attributes of amphibians and reptiles underlie all
is to facilitate studies of complex responses such as hor- aspects of their care: Ectothermy and diversity.
monal cycles, reproductive and social behavior, or water
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and temperature regulation. The welfare of the animals Ectothermy. Amphibians and reptiles are ectotherms,
must have the highest priority in the design of animal that is, they do not ordinarily generate enough metabolic
rooms, cages, and cage furnishings. This effort must not heat to raise their body temperatures above the ambient
be frustrated by the application of inappropriate stan- temperature. However, ectotherms are not literally "cold
dards based on domestic species. blooded." Under normal conditions, terrestrial ectotherms
Because most species of amphibians and reptiles are regulate body temperature by behavioral means, often at
not available on short notice or from commercial breed- high levels and within narrow limits. Several important
ing colonies, they are usually either collected from the implications for their care follow from this aspect of
wild by the investigators themselves, or obtained by gift their biology. Most importantly, they require environ-
from other researchers, zoos, or agencies such as the mental conditions quite different from those appropriate
U.S. Fish and Wildlife Service. The availability of a for birds and mammals.
species is likely to be affected by its seasonal activity Ectothermy is an energy-efficient mode of thermo-
cycle, the opportunity to collect in an exotic locality, and regulation because metabolic energy is not used to warm
the provisions of national laws and international treaties. the body. As a result, the resting metabolic rates, aerobic
An investigator who plans to travel thousands of miles capacities, and overall energy needs of ectotherms are
cannot predict in advance exactly how many individuals nearly an order of magnitude lower than those of endo-
of which species will be collected. As a consequence of therms (birds and mammals) of similar size (Figure 1).
this uncertainty, investigators may have to submit proto- The thermoregulatory mechanisms employed by am-
cols that include several taxa, only a few of which will phibians and reptiles are by no means simple. Many ecto-
actually be used. Furthermore, unusual species that have
been successfully acclimated to laboratory conditions have
a scientific value that transcends the project for which
they were originally collected, and they may be kept
indefinitely in expectation of further use. Animal care
and use committees must understand these practical as-
pects of working with amphibians and reptiles and evaluate
protocols accordingly.
THE BIOLOGY OF AMPHIBIANS
AND REPTILES
In order to design appropriate environments for amphib-
ians and reptiles, one must have an appreciation for their
unique biological characteristics. Some practices and I0g 100 g
materials that are suitable and desirable for the care of BODY MASS
birds and mammals are unimportant or even deleterious
for amphibians and reptiles. Conversely, considerations FIGURE 1 Resting metabolic rates of terrestrial vertebrates
that have little relevance for birds and mammals can be as a function of body size. Metabolic rates of salamanders are
crucial for successful husbandry of amphibians and rep- shown for 15°C and 25°C as the lower and upper limits of the
tiles. A large literature shows that husbandry practices darkened area, and data for all reptiles are shown at 20°C and
30°C. The metabolism-mass line for anurans falls within the
that are appropriate for mammals are not suitable for
"all reptiles" area, and the relation for non-passerine birds is
amphibians and reptiles, but the pertinent references are
similar to that for placental mammals. Dotted portions of the
scattered. Recent sources of general information about lines for birds and mammals show hypothetical extensions into
amphibians and reptiles include Bellairs (1969), National body sizes below the minimum sizes of most adult birds and
Academy of Sciences (1974), Harless and Morlock mammals. From Pough (1980), reprinted from The American
(1979), Stewart (1984a,b), Duellman and Trueb (1986), Naturalist by permission of The University of Chicago Press.
Halliday and Adler (1986), Seigel et al. (1987), Norris ©1980 by The University of Chicago Press.
S6 ILAR Newstherms regulate their body temperatures during activity from totally aquatic frogs to species that live in deserts.
at levels that are similar to those of birds and mammals Reptiles show still greater diversity in habitats and spe-
(35°C-42°C). The regulated temperature may change in cializations. Because the ecological characteristics and
response to internal and external conditions. Changes in husbandry requirements of the animals are so diverse, it
thermoregulatory behavior include differences between is impossible to formulate specific guidelines for groups
daytime and nighttime temperature, elevation of body larger than a few species. In fact, broad application of
temperature following feeding, increase or decrease in specific guidelines would inhibit rather than promote
body temperature during pregnancy, behavioral fever humane care.
mediated by prostaglandin release during bacterial infec-
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tion, and muscular thermogenesis during egg brooding
(Hutchison et al., 1966; Regal, 1966, 1967; Lillywhite et Sources of Information
al., 1973; Vaughn et al., 1974; Van Mierop and Barnard,
1976, 1978; Kluger, 1977, 1979; Hutchison and Erskine, The husbandry requirements of amphibians and reptiles
1981; Bartholomew, 1982; Beuchat, 1986; Sievert, 1989). in an academic setting are similar to those in zoos and
Humane care of amphibians and reptiles requires con- aquariums (Gans and Van den Sande, 1976; Gans, 1979;
ditions that facilitate their complex thermoregulatory Murphy and Campbell, 1987; Murphy and Chiszar, 1989),
responses. and research in zoos has been a fruitful source of infor-
mation about amphibians and reptiles (Sajdak, 1983).
Diversity. Living ectothermal tetrapods include nearly Publications for herpetological hobbyists often provide
4,000 species of amphibians and 6,000 species of rep- useful guides for care of ectothermal vertebrates (e.g.,
tiles. These 10,000 species display an enormous array Mattison, 1982, 1988; Obst et al., 1988; de Vosjoli, 1989,
of lifestyles, and it is this diversity that makes them 1990a, b; and journals like Lacerta, Reptile & Amphibian
attractive for research at the cellular or molecular level, Magazine, Salamandra, and Vivarium). Herpetological
as well as for studying organismal, ecological, and evo- Review, published by the Society for the Study of Am-
lutionary questions (Deuchar, 1975; Greenberg et al., phibians and Reptiles, has a section called "Herpetologi-
1989; Pough, 1989; Elinson et al., 1990). For example, cal Husbandry." The International Zoo Yearbook usu-
an investigator studying hormonal control of reproduc- ally contains sections about amphibians and reptiles, and
tive behavior can choose from some 3500 species of much of Volume 28 (1989) of this series was devoted to
anurans (frogs and toads). Among these are species that their care. Symposia, newsletters, and special publica-
retain an ancestral amphibian life cycle (terrestrial adults, tions of herpetological societies are also helpful sources
aquatic eggs, and aquatic larvae); terrestrial species in of information (e.g., Bowler, 1977; Murphy and Armstrong,
which either males or females carry developing eggs 1978; Ferner, 1979; Murphy and Collins, 1980; Gray and
and/or young on the back, in vocal pouches, and even in Bumgardner, 1984; Gray, 1985; Gowen, 1987, 1989; and
the stomach; species in which females feed their tadpoles the Bulletin of the Association of Amphibian and Reptil-
unfertilized eggs; and species that give birth to live young, ian Veterinarians). The professional staff at zoos and
either with or without some form of matrotrophic contri- aquariums can often provide advice about the husbandry
bution to the fetus. Moreover, anurans run the gamut requirements of a particular species. Such advice may be
Examples of diversity: The Puerto Rican coqui (Eleutherodactylus coqui) (left) is an entirely terrestrial frog. It can pass its entire
life without seeing a body of water larger than raindrops on a leaf. The elephant-trunk snake (Acrochordus javanicus) (right) is an
aquatic species that never emerges from the water. (Photos courtesy of F. Harvey Pough)
Volume 33, Number 4 FalM 991 S7particularly helpful in establishing breeding programs. Temperature. The thermoregulatory requirements of
Slavens (1989) publishes an annually-updated inventory amphibians and reptiles are different from those of birds
of reptiles and amphibians in zoos and private collec- and mammals and are more difficult to satisfy in captiv-
tions; this volume can lead to an appropriate source of ity. As endotherms, birds and mammals have continu-
information about a particular species. ously high rates of metabolic heat production, and ther-
The diversity exhibited by amphibians and reptiles moregulation consists primarily of adjusting the insulating
presents problems for husbandry that are not encountered value of hair or feathers to equalize the rates of heat
with domestic and laboratory birds and mammals. Hus- production and loss. Endotherms accomplish this regu-
bandry conditions must match the needs of the species lation over a broad range of air temperatures. The radia-
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being kept. Three factors are essential to achieve that goal: tive environments of the animal room and their cages
normally have little significance.
1. Knowledge of the natural history of each species, In contrast, amphibians and reptiles balance heat up-
obtained from field observations or from the literature; take from the environment with heat loss to the environ-
2. Duplication of the features of the animals' natural ment (Tracy, 1976, 1982). Control of the radiant envi-
microhabitats that are crucial for normal behavior and ronment of the cage (in both the infrared and visible
physiological function; and wavelengths) is especially important, because this is usu-
3. Awareness and sensitivity on the part of caretakers ally the major pathway of heat gain and loss. The thermo-
to the unique requirements of these animals and the ways regulatory behaviors of many species, especially rep-
in which they manifest ill-health. tiles, are based on adjusting position, posture, and reflectivity
in response to radiant flux. These animals may be unable
to respond appropriately to a uniform temperature or to a
GENERAL RECOMMENDATIONS FOR THE substrate temperature gradient. Lizards can be confused
CARE OF ECTOTHERMAL VERTEBRATES by unnatural combinations of temperature and light in-
tensity. For example, lizards controlled their body tem-
The following generalizations apply to the care of most peratures more effectively in gradients that provided the
amphibians and reptiles, but caution must be employed normal stimulus of bright light and heat at the same end
in their use. The taxonomic categories included are broad, of the gradient than they did in gradients that were uni-
and substantial variation exists within them. Some liz- formly lighted or in those that combined bright light
ards, for example, are heliothermic and regulate their with low temperatures (Sievert and Hutchison, 1991).
body temperatures between 38 and 42°C, whereas others Photothermal gradients employing incandescent bulbs
live beneath the canopies of tropical forests with body that produce both heat and light are probably the best
temperatures that fluctuate between 25 and 30°C. Still choice for long-term care (Regal, 1980). These gradients
others are nocturnal and active at body temperatures be- must provide cool retreat sites as well as warm basking
low 20°C. Similarly, some amphibians are entirely aquatic, spots for the animals. Because the body temperatures
whereas others may never see a body of water larger than that many species of lizards maintain during activity are
a pool of raindrops on a leaf. While these guidelines only a few degrees below their lethal temperatures, over-
emphasize the factors that are likely to be important for heating is a substantial risk if gradients are poorly de-
husbandry and point to general categories of problems signed. The cage must be large enough so that one end
and solutions, information about the ecology and physi- always remains cool, and cages that incorporate photo-
ology of the species being kept is indispensable. thermal gradients should never be covered with solid lids
that prevent the escape of heat. Shelters should be placed
along the length of the gradient so that animals are not
forced to choose between thermoregulation and security.
The Physical Environment In most cases, a variable temperature regime is necessary
(Regal, 1967, 1971). Animals kept continuously at the
Housing conditions must provide appropriate tempera- warm body temperatures they select voluntarily during
ture, moisture, and light regimes. In general, these in- activity may show deleterious physiological changes (Licht,
clude visible and ultraviolet light controlled on a daily 1965). Transient exposure to high temperatures may sup-
and seasonal cycle, water for drinking or bathing, and press the immune system of reptiles (Elliott Jacobson,
high relative humidity. High rates of air flow are not personal communication).
usually required in animal rooms housing amphibians Choosing the range of temperatures that should be
and reptiles. Limiting the number of air changes per provided for a particular species requires information
hour greatly simplifies the task of maintaining high hu- about its phylogenetic affinities and ecology. The ther-
midities. In most cases the key to successful care of moregulatory characteristics of groups of reptiles have
amphibians and reptiles lies in providing a gradient of been summarized (Avery, 1982). In particular, Ford (in
conditions within the cage that allows animals to select press) suggests appropriate temperatures for snakes. In
combinations of environmental factors needed. general, amphibians are less heliothermic than reptiles,
S8 ILAR Newsand the high rate of evaporative water loss characteristic 50
T SALAMANDERS
of amphibian skin counteracts radiant heat uptake (Lilly-
white, 1975; Tracy, 1976). Nonetheless, adult and larval
amphibians bask in the sun or use temperature gradients
to regulate body temperatures. A thermophilic response
after feeding and behavioral fever mediated by pros-
taglandin Ej have been reported for amphibians (Lillywhite
et al., 1973; Hutchison and Erskine, 1981). Substrate
temperature gradients produced by heating elements be-
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neath the cage floor may be more effective than photother-
mal gradients, especially for nocturnal or secretive am-
phibians. The thermoregulatory characteristics of amphibians
have been summarized (Brattstrom, 1979; Hutchison, in AMPHISBAENIANS
press), and information about salamanders can be found
in Feder et al. (1982) and the references therein.
Water. A shallow container of water is appropriate for
many amphibians and reptiles. However, some tropical
10 tO IOO
species require daily spraying, and some desert reptiles ADULT BODY MASS (g)
never drink. Amphibians do not drink; terrestrial species
absorb water through the skin and anurans have an area FIGURE 2 Adult body masses of amphibians and reptiles.
of skin in the pelvic region that is specialized for this The percentages of the total number of taxa surveyed with body
masses in the ranges 100
function. Shallow water dishes, moist substrates, and
g are shown. Sample sizes: salamanders, n = 198; anurans, n =
spraying are appropriate for terrestrial amphibians. Chlo- 1,330; caecilians, n = 160; snakes, n = 1,592; lizards, n =
rinated water should be avoided, especially for aquatic 1,780; amphisbaenians, n = 110. From Pough (1983), reprinted
amphibians, and water bowls should be changed as often by permission of the Ohio State University Press.
as practical because Pseudomonas populations increase
rapidly in stagnant water (Elliott Jacobson, personal
communication).
95 percent of the salamanders have adult body masses
Humidity and Air Flow. Most amphibians and reptiles smaller than 20 g (Figure 2). Indeed, 8 percent of liz-
are much smaller than laboratory mice (Pough, 1980, ards, 17 percent of frogs, and 20 percent of salamanders
1983). An adult white mouse weighs about 20 g, while weigh less than 1 g as adults! These very small body
nearly 80 percent of the species of lizards and frogs and sizes have important implications for husbandry (Pough,
in press). In their natural environments, most amphib-
ians and reptiles spend their time at the ground surface,
under leaf litter, or in burrows. As a result they are
exposed to microclimates (especially humidities and rates
of air movement) that are very different from those per-
ceived by large animals like humans. Even desert spe-
cies spend much of their time in burrows or buried in
loose sand. Relative humidity approaches saturation in
these microhabitats, and the low humidities characteris-
tic of heated and air-conditioned buildings can be stress-
ful even for desert reptiles. Relative humidities should
be maintained above 70 percent (preferably at 80 per-
cent) for nearly all species of amphibians and reptiles.
However, most reptiles develop skin lesions when they
are kept on wet substrates for long periods.
Amphibians can often be kept in cages with lids to
keep humidity high, but many reptiles require photother-
Desert lizards like the Coachella Valley fringe-toed lizard (Uma
mal gradients. Putting a lid over a photothermal gradient
inornata) live in regions where the average annual rainfall is
less than 20 cm. One would expect animals from such habitats
quickly leads to lethal overheating of the animals inside.
to be tolerant of dryness, but these lizards spend much of their Instead, it is necessary to maintain high relative humidity
time underground where humidity is close to saturation. In in the entire animal room. Room air flow can be limited
captivity even desert reptiles require high relative humidities. to a maximum of one or two changes per hour to main-
(Photo courtesy of F. Harvey Pough). tain the humidities these animals require.
Volume 33, Number 4 Fall 1991 S9The large number of incandescent lights required in a
room that houses 20 or 30 cages of lizards or snakes may
produce more heat than the air-handling system can ex-
haust, especially when the number of air changes per
hour is restricted to keep the relative humidity high. It is
wise to incorporate thermostats to turn off the lights
when room temperature approaches a level that is stress-
ful for the least heat-tolerant species.
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Light. Quality and quantity of light may both be impor-
tant to amphibians and reptiles. An annual cycle of day
length is usually critical, especially for breeding colonies.
Windows or skylights that admit bright sunlight without
overheating the room are ideal, but are rarely included in
animal rooms. In lieu of natural daylight cycles, timers Cages for desert lizards. An incandescent lamp at one end of
can be used to control photoperiod on an annual cycle. each cage creates a temperature gradient, and black light and
The wavelengths of light provided to captive amphib- sunlamp fluorescent tubes provide ultraviolet radiation. (Photo
ians and reptiles also require attention, but little is known courtesy of F. Harvey Pough).
about the effects of different light intensities and of vary-
ing ratios of wavelengths. A trial-and-error approach has
been adopted by zoos and individuals who maintain these reptiles, nor do we know whether the ratio of middle-
animals, and this body of anecdote constitutes nearly all wavelength (290 to 315nm) to long-wavelength (315 to
the information currently available for most species. 400nm) ultraviolet light (UVA) is important. Gehrmann
Providing the proper amount and quality of ultraviolet (1987) presented information about the spectra of sev-
light is probably the most difficult aspect of lighting. eral bulbs used in animal husbandry. Broad-spectrum
Some species of amphibians and reptiles appear to re- fluorescent bulbs such as Vita-Lite® (Duro-test) and
quire ultraviolet light for calcium metabolism, normal Chroma 50® (General Electric) may be effective (Regal,
behavior, and reproduction (Cole and Townsend, 1977; 1980), although these lights, especially the Chroma 50
Laszlo, 1969; Moehn, 1974; Townsend, 1979; Townsend bulb, emit little energy in the middle-wavelength ultra-
and Cole, 1985; Regal, 1980). Middle-wavelength ultra- violet portion of the spectrum. (Note that, contrary to
violet light (UVB) penetrates the epidermis and converts common misconception among hobbyists, Gro-Lux®
provitamin D 3 to previtamin D 3 . Synthesis of the active bulbs do not emit much ultraviolet light, and they are
form of the vitamin (1,25-dihydroxyvitamin D3) by birds not appropriate for UV supplementation, although they
and mammals has been studied, but the process is not may be used in displays to support plant growth without
well understood for amphibians and reptiles, some of harm to animals) (Roberts and Gehrmann, 1990). Fluo-
which have as many as six types of provitamin D 3 in their rescent BL (black light) bulbs provide long-wavelength
skins (Holick, 1989a). ultraviolet light (UVA). Bulbs designated BLB (black-
Some diurnal reptiles from open habitats have layers light blue) have a filter that passes only ultraviolet wave-
of melanin in the skin that block penetration of ultravio- lengths; they are more expensive than BL bulbs, but no
let light (Porter, 1967). These animals might require more effective for animal husbandry. Neither a twelve-
higher intensities of light than do species with more hour daily exposure to Vita-Lite® nor a half-hour expo-
translucent skins. Preliminary information from work at sure to a Sylvania BL bulb was sufficient for normal
the National Zoo suggests that green iguanas (Iguana calcification of young chickens (Bernard et al., 1989),
iguana) cannot use dietary vitamin D 3 , and must receive and the authors recommended that these bulbs not be
ultraviolet light for maintenance of blood levels of 1,25- used for captive animals.
dihydroxyvitamin D 3 (Mary Allen, personal communi- Middle-wavelength ultraviolet light (UVB) is provided
cation). Similarly, birds and mammals synthesize two by fluorescent sunlamp bulbs of the sort sometimes used
types of vitamin D 3 , and dietary 1,25-dihydroxyvitamin in treating psoriasis. In addition to the familiar tubular
D 3 would not substitute for cutaneous synthesis of 24- fluorescent sunlamps, self-ballasted reflector mushroom-
dehydrovitamin D 3 (Holick, 1989b). However, several type mercury lamps emit UVA and UVB radiation (Wil-
species of lizards have been raised successfully without liam H. Gehrmann, personal communication). They are
ultraviolet light, in some cases for two or more genera- manufactured in 160 and 250 watt sizes by Philips Light-
tions, using dietary supplementation to provide vitamin ing Company and Iwaski Electric Company. National
D 3 (Larry Talent, personal communication; Gehrmann Biological Corporation (1532 Enterprise Parkway,
etal., 1991). Twinsburg, OH 44087) is a source of UVA and UVB
We do not know exactly what wavelengths of light are bulbs. Middle-wavelength ultraviolet light can injure the
required for vitamin D 3 synthesis by amphibians and eyes of animals and caretakers, and precautions should be
S10 ILAR Newstaken to limit exposure. Species of reptiles differ sub-
stantially in the UV exposure they require (Townsend
and Cole, 1985; Gehrmann, 1987), and a conservative
approach is advised. Exposure periods of 30-45 minutes
at a distance of 50 cm from a UVB lamp may be satisfac-
tory for reptiles from open habitats (Moyle, 1989). UV
irradiance at the midpoint of tubular bulbs is about twice
as intense as irradiance at the ends (Gehrmann, 1987).
Breaking the daily UVB exposure into 10-15 minute pe-
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riods at hourly intervals may help to ensure that all the
individuals in a community cage have access to the light.
Snakes may normally satisfy their vitamin D 3 require-
ments from their diet of whole animals (Ford, in press).
Reptiles from forests, and amphibians in general, are
probably more sensitive to UV light than are desert rep- Dart-poison frogs (Colostethus) deposit eggs in folded leaves.
tiles, and UVB bulbs are probably not appropriate for The eggs are attended by a parent during development. When
these animals. Early signs of UVB toxicity include fail- the eggs hatch, the tadpoles are transported to water on the back
ure to eat, lethargy, diminished activity, and a gray or of the adult frog. (Photo courtesy of F. Harvey Pough).
smokey skin color that turns progressively darker (Wil-
liam Gehrmann, personal communication). All of these
symptoms appear to be reversible when exposure ceases.
Considering the potential risk posed by UVB bulbs to effective care and sanitation. Providing hiding places is
reptiles and their caretakers, a combination of broad- of paramount importance for nearly all species.
spectrum fluorescent bulbs and long-wavelength (UVA)
bulbs is probably the most practical starting point for Cage Furnishings. Cage and aquarium props (e.g., branches,
husbandry of a species with unknown requirements rocks, and substrate) should complement the normal life-
(Townsend and Cole, 1985). The bulbs should be as style of the animal. A varied cage environment may be
close as possible to the tops of the cages, preferably necessary for normal behavior; for example, the thermo-
within 15-20 cm of the animals. However, if symptoms regulatory and foraging behaviors of Lacerta vivipara
of vitamin D 3 deficiency are observed, it may be wise to break down in the absence of spatial diversity (Roger A.
consider providing a source of UVB radiation. Avery, personal communication). Many species of am-
Because glass does not transmit middle-wavelength phibians and reptiles require materials that duplicate their
ultraviolet light and greatly attenuates longer wave- natural settings for breeding. Terrestrial frogs such as
lengths, it should not be used for cage tops. Wire mesh Eleutherodactylus, Dendrobates, and Colostethus breed
and some acrylic plastics and fluoroplastics transmit in captivity when they are given suitable nest sites. In
short-wavelength ultraviolet light and are suitable for nature these species deposit their eggs in smooth-
cage tops (Gehrmann, 1987). surfaced fallen leaves, which should be included in the
The ultraviolet output of fluorescent bulbs decreases cage. Nearly all animals require a hiding place; opaque
substantially after a few hundred to a few thousand plastic boxes with small entrance holes make good re-
hours of use. Unfortunately, this change is not apparent treat sites, and have the merit of being easily cleaned.
to the human eye, and can be easily overlooked until the Thigmotaxic stimuli may be nearly as important as the
animals' health is affected. Manufacturers can provide darkness that opaque shelters provide. Cobras used trans-
information about the useful life of their bulbs, and a parent plastic boxes as regularly as they used opaque
regular schedule of changing bulbs will ensure that the boxes for hiding places when the two kinds were tested
animals are receiving ultraviolet light (Townsend and sequentially. However, in simultaneous presentations,
Cole, 1985). the snakes always chose the opaque box (Chiszar et al.,
1987). It can be advantageous to be able to see an animal
when it is in its retreat, and some situations may warrant
The Biological Environment the use of transparent shelters.
Amphibians and reptiles often ingest bedding material
Most amphibians and reptiles are secretive. They live in with food, and cage substrates should be chosen with this
close association with their structural microenvironments, possibility in mind. Several substrates commonly used
and subtle cues—scent, texture, contact—are important for bird and mammal cages are harmful for amphibians
aspects of their behavior. Animals of this sort do not and reptiles. Appropriate substrates keep the animal dry,
thrive in barren steel cages or in plastic boxes filled with such as newspaper, indoor-outdoor carpet, sand (only for
wood shavings; their husbandry requires housing that species that normally live in sand), gravel (smooth par-
combines the animals' need for environmental cues with ticles that are fine enough to pass through the digestive
Volume 33, Number 4 Fall 1991 S11tract), crushed oyster shells (especially good for tortoises,
large lizards, and snakes), hardwood mulch and bark
chips, and peat and sphagnum moss. Materials that swell
when they are swallowed, such as ground corn cobs,
kitty litter, the pine shavings used in rodent cages, and
cocoa shells, should not be used (Demeter, 1989). Cedar
shavings have neurotoxic properties and should not be
used (Elliott Jacobson, personal communication). Aspen
shavings (Animal Bedding #2, American Excelsior Co.,
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Arlington, TX) have proven satisfactory for snakes (Ford,
in press).
Many animals press their snouts against the walls of
their cage as they explore, and rough or sharp surfaces
may injure them.
The Solomon Islands prehensile-tailed skink (Corucia zebrata)
Behavioral Interactions. Many amphibians and reptiles benefits from having branches in the cage to climb. (Photo
are territorial in the field, and in captivity often form courtesy of F. Harvey Pough).
dominance hierarchies. Initially the establishment of
these dominant-subordinate relationships is likely to in-
volve fighting and the risk of injury, especially because implications for management (Lang, 1987), and the be-
the loser is unable to leave the cage. After hierarchies havioral consequences of raising and maintaining croc-
have stabilized, low-ranking individuals may be excluded odilians in isolation have not been studied. The possibil-
from feeding, basking, or retreat sites (Regal, 1971). ity that behavioral imprinting of juveniles occurs during
Aggressive behavior often waxes and wanes seasonally. their association with their parents should be considered
For example, courtship can lead to injury of a female that in husbandry programs.
rejects a male's advances but is unable to escape from Some lizards and snakes employ communal defeca-
him. Caretakers must be alert to subtle departures from tion, hiding, or egg-laying sites. Several lizards and a
normal behavior that indicate incipient problems, as well few snakes remain with their eggs, and prolonged asso-
as to the appearance of wounds and new scars. ciation between mother and offspring has been reported
Caretakers must also be aware of the sensory worlds for the Solomon Islands prehensile-tailed skink, Corucia
of the animals and the stimuli that are important to them. zebrata (John Groves, personal communication). Paren-
For example, it is stressful for a plethodontid salamander tal care by some species of frogs extends to association
to be moved into a cage that bears the scent of another between an adult and its tadpoles or hatchlings (see Duell-
individual, or to have pheromones from another sala- man and Trueb (1986) for examples). I suspect that
mander deposited on its body during handling (Jaeger, in social interactions are more widespread among amphib-
press). Ovarian development of female lizards (Anolis ians and reptiles than we currently realize, and in some
carolinensis) has been reported to be accelerated by the cases may be components of successful husbandry.
sight of male lizards giving courtship displays, and re-
tarded by watching aggressive interactions between Food. The type of food and the rate of feeding should, at
males (Crews, 1975). a minimum, ensure normal growth or maintenance of
Social interactions may be important components of weight. (The nutritional requirements of breeding ani-
the biology of some amphibians and reptiles. Crocodil- mals may be different from those only being maintained.)
ians appear to be the most social reptiles, and parental The low metabolic rates and high conversion efficiencies
care for young after hatching is probably universal among of ectotherms means that overfeeding of captive animals
crocodilians (Lang, 1987). Sibling groups of young croc- is more common than underfeeding. The food require-
odilians remain with one or both parents for extended ments of amphibians and reptiles vary widely; some spe-
periods—as long as 24 months for the American alligator cies require nearly daily feeding, whereas others do best
(Garrick and Lang, 1977; Hutton, 1989). Young Ameri- on three, two, or even one feeding per week. Very large
can alligators spend the day together, basking on land or snakes may benefit from still longer intervals between
moving back and forth between land and water. At night meals. In general, if a healthy animal that has adjusted
the individuals disperse to forage, reassembling in the to captivity does not accept food soon after it is offered,
morning (Deitz, 1979 (quoted in Lang, 1987)). Vocal- the food should be removed and the animal allowed to
izations by juveniles and adults assist in maintaining fast until the next feeding time. In salamanders, croc-
these groups, and a distress call from a juvenile brings an odilians, snakes, and lizards emaciation is first visible as
adult to the rescue. Juvenile and adult crocodilians may concavity at the base of the tail and prominence of the
continue to associate in social groups, sometimes segre- lateral processes of the caudal vertebrae. The pelvic
gated by age and sex. These social interactions have girdle of emaciated frogs is clearly outlined. While turtles
S12 ILAR Newsexhibit fewer conspicuous signs of emaciation, with ex- Live Food. Many amphibians and reptiles respond to
perience it becomes easy to recognize a turtle that feels movement and will ignore even their favorite prey if it is
too light for its size. motionless. Live food is required for these animals, and
The foods that can be provided to amphibians and husbandry of amphibians and reptiles often requires
reptiles in captivity rarely resemble their natural diets, maintaining colonies of insects as well.
and the nutritional requirements of amphibians and rep- Insects. Diets that alternate different kinds of live
tiles are poorly understood. A varied diet is likely to be food are desirable, and a diet consisting solely of meal-
more nutritious and more readily accepted than a diet worms is notoriously unsatisfactory (e.g., Demeter, 1989).
consisting of only one kind of food. Providing balanced A combination of crickets (Acheta), mealworms (Tenebrio
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nutrition for amphibians and reptiles is challenging, and larvae), flour beetle larvae (Tribolium) and wax moth
a variety of opinions can be found in the literature. The (Galleria) or fly larvae (Sarcophaga) is suitable for in-
following paragraphs emphasize points of agreement, but sectivorous lizards and amphibians. Roaches (Blaberus),
the references should be consulted for additional infor- king mealworms (Zoophobias), and fruit flies (Drosophila)
mation and dissenting views. are also standard food items for captive amphibians and
reptiles. The insects must be healthy and well-fed if they
Vitamins and Minerals. The routine use of supplemen- are to be nutritious food. Insects that are not eaten prompt-
tary vitamins and calcium is often advised for amphib- ly should be removed from cages, because they may
ians and reptiles (Campbell and Busack, 1979; Allen et attack the animals. Suggested diets and instructions for
al., 1986; de Vosjoli, 1990a; Staton et al., 1990), but care of insects and other invertebrates are available in
generalizations about the quantities needed are difficult The Encyclopedia of Live Foods (Masters, 1975), the
to formulate. Studies of lizards have revealed substantial Carolina Arthropods Manual (Anonymous, 1982), and
interspecific and geographic variation in vitamin and mineral The Right Way to Feed Insect-eating Lizards (de Vosjoli,
requirements, and the symptoms of vitamin deficiency or 1990a). Mary Allen (National Zoo) recommends mon-
excess are similarly variable (Larry Talent, personal key chow and dog kibble as a stock cricket diet.
communication). Many multivitamin supplements don't The material in the gut of insects is an important
state nutrient levels on their labels. Using a product source of nutrients for amphibians and reptiles, and in-
without knowing whether it has, for example, 5000 or sects can be nutrient-loaded to increase their food value.
50,000 IU of vitamin A per gram is dangerous (Mary A high-calcium diet for crickets (Cricket diet #39-390) is
Allen, personal communication). available from Ziegler Bros., Inc. (PO Box 95, Gardners,
As with UVB supplementation, we remain largely at a PA 17325). This diet is intended for calcium-loading
trial-and-error stage, and a conservative approach to vi- crickets before they are fed to amphibians and reptiles; it
tamin supplementation is probably the best starting point is not suitable for rearing crickets. The gastrointestinal
for a species with unknown requirements. Selective sup- tracts of crickets contained detectable quantities of cal-
plementation of particular nutrients is preferable to a cium and phosphorus after 48 hours on the high-calcium
shotgun approach. For example, a calcium:phosphorus diet (see Allen and Oftedahl, 1989 for details and sug-
ratio of 1.5:1 promotes normal bone growth. gestions).
Food items can be dusted with a vitamin-mineral mix- Birds and Mammals. Mice, rats, and hatchling chick-
ture just before they are offered to the animals; uneaten ens or quail should be euthanized by an approved method
items should be removed from the cage. Most insects that does not leave a toxic chemical residue before they
have low levels of calcium, and dusting them with a are fed to captive amphibians and reptiles. Asphyxiation
calcium/phosoporous mixture that adjusts the ratio is with carbon dioxide is a satisfactory method of killing
desirable. D-Ca-Fos® (Fort Dodge Labs, Fort Dodge, IA animals for this purpose.
50501) is a finely powdered mixture of vitamin D, cal-
cium and phosphorus that can be applied to insects as Prepared Diets. Although many amphibians and rep-
small as fruit flies and pinhead crickets. Beta-carotene tiles have narrow dietary preferences, some species can
and vitamins C and E may also be beneficial, but exces- be trained to accept prepared foods that incorporate vita-
sive vitamin and mineral supplementation can cause min and mineral supplements. Good candidates for such
problems (de Vosjoli 1990a). Feeding a balanced diet is dietary shifts are lizards and snakes that rely on scent to
preferable to supplementing an inadequate one. identify food. Skinks (Eumeces, Chalcides, and many
The diets of anurans can be supplemented by putting other genera), tegus and dwarf tegus (Tupinambis and
slow-moving insects, such as mealworms and wax moth Callopistes), monitor lizards (Varanus), and natricine snakes
larvae in shallow dishes with powdered vitamins and (Thamnophis, Nerodia, and related genera) will often
minerals. When the frogs catch the insects, some of the learn to accept canned cat and dog food. The odor of a
powder adheres to their tongues and is ingested with the fish-based food is sometimes particularly attractive, even
prey. Many lizards will eat a mixture of dry vitamin and to species that never see a fish in their natural state.
mineral powders and fine silica sand from a dish (Larry Dietary shifts can be facilitated by introducing them grad-
Talent, personal communication). ually, a time-honored technique among reptile keepers
Volume 33, Number 4 Fall 1991 S13(Weldon et al., in press). For example, a lizard that eats (Troyer, 1982, 1984c). Thus, juvenile folivores hatched
mice can initially be given mice with progressively more in captivity and isolated from sources of normal symbi-
cat food spread on the fur, then cat food in a dish gar- onts probably do not have their species' typical comple-
nished with portions of a mouse carcass, and finally plain ment of fermentative microorganisms. Although these
cat food. Not all of the commercial foods for reptiles and individuals may grow and prosper on diets that do not
amphibians that are sold in pet stores provide a well- require fermentation of plant cell walls, their digestive
balanced diet, and advice about specific products should physiology is probably not typical of free-ranging indi-
be sought from a qualified source. Many of the major viduals. This observation has important implications for
zoos now have nutritionists who can provide helpful laboratory studies that assume their subjects to be in a
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information. normal physiological state, and for husbandry programs
that rear juveniles for release. In situations when diges-
Herbivorous Reptiles. Many species of reptiles include tive physiology is important, husbandry of folivorous
some plant material in their diets. The most specialized reptiles should probably include a method of inoculating
of these are folivores (leaf-eaters). Prominent in this group hatchlings with the species' typical gut symbionts. This
are large lizards such as chuckwallas (Sauromalus), may be a matter of substantial applied significance, be-
green iguanas (Iguana), ground iguanas (Cyclura), the cause many folivorous species of reptiles are threatened
Galapagos marine and land iguanas (Amblyrhynchus and or endangered, and captive breeding programs for some
Conolophus), Fijian iguanas (Brachylophus), mastigures of them are planned or in progress (Bjorndal, 1981; Burghardt
(Uromastyx), the East Indian water lizard (Hydrosaurus), and Rand, 1982; Miller, 1987; IUCN, 1989; Swingland
and the green sea turtle (Chelonia mydas). These species and Klemens, 1989).
rely on fermentative digestion and show characteristic
morphological and physiological specializations of the Housing and Sanitation. Housing conditions should
gut (Iverson, 1982; McBee and McBee, 1982; Troyer, inhibit the presence and spread of disease. However,
1983, 1984a; Bjorndal, 1985; Bjorndal andBolten, 1990). sanitation protocols should not frequently disturb the animals
Food particle size, the ratio of fruit to foliage, and the nor require complete removal of feces because many
ratio of plant to animal material can affect digestibility ectothermal vertebrates use pheromones, including con-
and the assimilation of energy and nutrients by herbivo- stituents of feces, for intraspecific communication. Snakes
rous reptiles (Bjorndal, 1989, 1991; Bjorndal et al. 1990). kept in clean cages spend more time attempting to escape
Nutritionally complete diets for herbivorous reptiles than do individuals in cages where a small amount of
are commercially available. Ziegler Bros., Inc. (PO Box fecal matter is left each time the cage is cleaned (Chiszar
95, Gardners, PA 17325) makes 15 percent and 25 per- et al., 1980). Similarly, plethodontid salamanders mark
cent crude protein meal-type diets for iguanas, and a their cages with pheromones in their feces, and salamanders
variation of that diet in small pellets for desert tortoises. in freshly cleaned cages make more attempts to escape
Marion Zoological (Marion, Kansas) makes an extruded than do salamanders in cages they have marked with
diet of very small diameter for herbivorous reptiles. A their own scent (Jaeger, 1986 and references therein).
mixture of 10 parts by weight of leafy greens to one part Thus, excessive cleaning or sterilization of cages can be
soaked dry dog food is a good alternative. The dog food deleterious to the well-being of the animals. The human
should be soaked just enough to soften it because excess nose is the most appropriate guide to cleanliness: No
water can leach out nutrients (Mary Allen, personal odor of waste products should be perceptible in the air
communication). Chopped alfalfa hay is also accepted of a room housing ectothermal animals. Application of
by tortoises, especially when it is mixed with greens. this criterion is practical and effective because unsani-
The specializations of folivorous reptiles extend be- tary conditions are readily detected when the number
yond morphology and physiology to include behavior of changes of room air per hour is limited to maintain
and ecology, and these phenomena must be considered in the high relative humidities amphibians and reptiles
husbandry. Like all folivores, reptiles are selective about require.
the species and the parts of plants they eat. Juvenile Through-flow aquatic systems are less likely to spread
iguanas choose leaves with low fiber and high protein pathogens than are recirculating systems. Chlorine should
content, and they accelerate digestion by maintaining be removed from incoming water, which should be heated
body temperatures higher than those of adults (Troyer, or cooled to the appropriate temperature before it is in-
1984b, 1987). Social behavior probably also contributes troduced to the animals' tanks. If a recirculating water
to folivory for iguanas. Newly hatched green iguanas system is necessary, each tank should have a self-con-
spend a short time in the tropical forest canopy where tained system to minimize the chances of cross-contami-
adult iguanas live before returning to the forest-edge nation. A sterilization process may be a desirable com-
vegetation where they remain during their growth as ju- ponent of recirculating aquatic systems.
veniles. Apparently this brief association of hatchlings Separate quarantine facilities are highly desirable for
with adults facilitates the transfer of the gut symbionts amphibians and reptiles, and newly arrived animals should
responsible for fermentative digestion of plant matter be kept in cages isolated from long-term stock for at least
S14 ILAR News90 days (Elliott Jacobson, personal communication). Checks 20°C) are appropriate for tropical species. Most animals
for parasites should be routine. These tests contribute to do not become torpid under these conditions, but emerge
the health of the caretakers as well as to the welfare of from their hiding places during the day and retreat at
the animals. night. A short photoperiod is more natural than contin-
uous darkness, and a daily temperature cycle may be
desirable. Dehydration is a risk in environmental cham-
MARKING INDIVIDUALS bers that regulate temperature by passing air over refrig-
erating coils. The cages must prevent excessive water
The ability to recognize individuals is critical to many loss without allowing the continuous contact with wet
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studies, and methods of marking amphibians and reptiles substrates that is likely to produce skin lesions. As the
were reviewed by Ferner (1979). In many instances end of the cool period approaches, the photoperiod
individual variations in pattern allow even large numbers should be lengthened and the temperature gradually in-
of animals to be distinguished without artificial marks. creased. Animals undergoing this treatment are not in
When this is not possible, several techniques can be any sense in cold storage or suspended animation, and
employed, depending on whether long-term or short- water dishes should be cleaned and refilled daily.
term marks are needed. Clipping off portions of toes or Seasons in some habitats, particularly in the tropics,
scales has traditionally been used to mark individuals, are distinguished more clearly by rainfall patterns than
but toe clipping in particular is painful and may affect by temperature cycles. Animals from these habitats may
locomotor ability, especially for arboreal species. Fur- be induced to breed by simulated rain showers. This
thermore, some individuals regenerate the clipped toes method was used by the Metropolitan Toronto Zoo to
or lose additional toes in fights. Freeze-branding ap- breed Puerto Rican crested toads (Peltophryne lemur)
pears to produce a mark that lasts one or two seasons. (Paine et al., 1989). The breeding schedule is keyed to
Passive integrated transponders (PIT tags) have been used environmental conditions in the toads' natural habitat.
successfully to mark amphibians and reptiles, and this In December, which corresponds to the late part of the
appears to be the best method of permanently marking rainy season in Puerto Rico, feeding is increased, and
species that are large enough to accommodate the tag females receive newborn mice dusted with vitamin D 3
(Camper and Dixon, 1988). and calcium supplements. In late January, when the dry
season is beginning, the toads are put into a cage that
has been filled with a water-soaked mixture of peat and
BREEDING sphagnum mosses. Ambient temperature is about 22°C,
and the relative humidity is 50 to 70 percent. The toads
The reproductive cycles of amphibians and reptiles are burrow into the substrate, which dries slowly during the
closely linked to their physical and biological environ- next month. A shallow water dish in the cage allows the
ments, and effective breeding programs employ manipu- toads to rehydrate when they emerge from the substrate
lation of these factors (e.g, Crews and Garrick, 1980). at night. The toads are dug out of the moss and fed
Case-studies are published in the newsletters and sympo- weekly. Feeding ceases at about the time the moss dries
sia of herpetological societies, the International Zoo Year- completely. The toads are kept for another month in
book, and hobbyist literature. As with most other aspects the dry substrate, and checked regularly to see that they
of herpetological husbandry, we are at the stage of trial remain hydrated.
and error, and investigators should seek information about At the end of 60 days of dryness, a time that corre-
the species of interest to them from those publications sponds to the usual onset of the Puerto Rican rainy sea-
and from the staffs of zoos and aquaria, many of which son, water is added gradually for two days until the moss
have successful breeding programs for several species. is saturated with water, and the air temperature is raised
Some generalizations will provide a starting point for to 27°C. On the morning of the third day, the males are
establishing breeding programs. For example, manipu- transferred to tanks of water in which cultures of algae
lating temperature, humidity, and photoperiod on an an- have been established. A spray of water simulates rain-
nual cycle has been effective for many species. A period fall, and tape recorded mating calls of the toads are
of 1 to 4 months of low temperature stimulates breeding played to both sexes. The males are left in the breeding
for a variety of reptiles and amphibians, including some tanks for two days before the females are added. The
tropical species. This method has been applied success- presence of a group of toads appears to contribute to
fully to snakes (e.g., Scheidt, 1984; Tryon and Whitehead, the formation of amplexing pairs, and amplexus nor-
1988), as well as to lizards, turtles, and amphibians. mally begins very soon after the females are introduced.
Animals must be allowed to fast before they are cooled, The simulated rainfall and recordings of mating calls are
and a gradual reduction in temperature over a period continued for another three or four days.
of days is preferable to an abrupt change. Environmental The Toronto Zoo's program illustrates the effective-
temperatures can be lowered to 10°C for species from ness of techniques that initiate the physiological changes
temperate zones, whereas warmer temperatures (18°C- associated with breeding by manipulating the physical
Volume 33, Number 4 Fall 1991 S15You can also read
