Husbandry and Breeding of the Crocodile Lizard (Shinisaurus crocodilurus) at Woodland Park
Zoo, Seattle, Washington, USA
Linda T. Uyeda - PhD Student, University of Washington / Zookeeper, Woodland Park Zoo
Diane Yoshimi - Zookeeper, Woodland Park Zoo
The "Day House" (reptile and amphibian unit) at the Woodland Park Zoo in Seattle,
Washington, USA has been involved in the husbandry and breeding of Shinisaurus crocodilurus since
1993, producing a total of 59 offspring. The current Woodland Park Zoo Shinisaurus collection is
housed entirely indoors and consists of 15 individuals. Individuals in Woodland Park Zoo’s
Shinisaurus collection exhibit a shorter time to fertility and breeding cycles that do not correspond to
behavior previously observed in wild and other captive populations. Woodland Park Zoo’s husbandry
parameters and other data from the breeding program will be discussed.
The Chinese Crocodile Lizard, Shinisaurus crocodilurus, is a monotypic genus in the knob-scaled
lizard family Xenosauridae. Measuring up to 45cm total length, Shinisaurus is a semi-aquatic,
predatory native to the Guangxi and Guangdong provinces of China and the Quang Nihn province in
Vietnam. Eight isolated Shinisaurus populations exist in China, with the small Vietnamese population
only recently discovered (Le and Ziegler 2003). Preliminary comparative analysis has determined the
Vietnamese population to be genetically indistinct, despite Chinese and Vietnamese populations being
separated by at least 500 km (Ziegler et al. 2008). Since 1978, six transect surveys have been
conducted in China, documenting a rapid decline in overall Shinisaurus populations with the total
estimated Chinese population decreasing from 6,000 individuals in 1978 to 950 individuals in 2008
(Huang et al. 2008). Poaching for pets, food, and medicine is considered the greatest threat to wild
populations, with habitat destruction and local environmental changes also playing a role in the
populations’ severe decline. Though Shinisaurus is currently categorized as “Vulnerable” by the IUCN
(Huang et al. 2008) and has been listed on CITES appendix II since 1990 (CITES 2010), significant
decreases in wild population levels and continued threats to habitat have prompted researchers to
propose an enhanced conservation status and greater conservation measures (Huang et al. 2008,
Ziegler et al. 2008).
A severe and continued decline of wild Shinisaurus populations throughout the past 30 years
has resulted in an emphasis on population management, in-situ conservation programs, and captive
breeding to aid in preserving this species. Shinisaurus captive breeding programs exist throughout the
world in zoological institutions and in the collections of hobbyists and breeders. However, long and
variable gestation periods ranging from 8 to 14 months (Visser 1989, Hofmann 2000) coupled with
precise captive husbandry requirements create challenges for those attempting captive propagation.
According to the North American Regional Studbook: Chinese Crocodile Lizard (Shinisaurus
crocodilurus) (Fresno Chaffee Zoo 2007), as of November 2007, there were only 127 living specimens
at 21 Association of Zoos and Aquariums (AZA) accredited institutions throughout North America,
parts of China, and Germany
. AZA Member institutions breed individuals according to the population
management plan dictated by the Studbook, and each institution’s collection is also managed based on
comprehensive breeding recommendations.
Woodland Park Zoo “Day House”, Seattle, Washington
The Woodland Park Zoo (WPZ) is a 92-acre (~ 37 hectare) zoological facility housing over
1000 individuals and approximately 300 different animal species. The “Day House” (reptile and
amphibian) unit is currently home to over 100 individuals across 58 taxa, including a breeding
collection of Shinisaurus crocodilurus. The current Shinisaurus collection consists of 15 individuals: 5
neonates, 5 adult males, and 5 adult females.
WPZ’s adults are housed in enclosures ranging from 50cm x 30cm x 25cm tanks for individuals
to fish stock tanks (190cm x 80cm x 44cm deep) for a breeding pair. Males cannot be housed together
due to potential issues associated with aggression (Visser 1989; Yoshimi pers. obs.). Each enclosure
contains rocks and branches for basking, and artificial plants as refugia, with tanks generally placed at
an angle to provide both wet and dry areas.
Each of WPZ’s enclosures is equipped with a fluorescent UVB bulb as well as incandescent heat
lamps to provide a temperature gradient and warmer basking spots. Throughout the year, light cycles
are changed to reflect seasonal day lengths based on a latitude of 23
according to the following
Jan 1 – 6:45am-5:30pm
Apr 1 – 5:45am-6:15pm
Jul 1 – 5:15am – 7:00pm
Oct 1 – 6:00am-5:45pm
To prevent excessive weight loss during a winter period in which the animals stop eating,
basking lights are turned off after cessation of eating is observed in October and turned on again after
eating is resumed around February.
WPZ enclosures are cleaned every other day by draining, disinfecting, and filling with
untreated tap water at 21-22
C. As the temperature of each enclosure is not independently regulated,
Privately held, non-AZA specimens are not considered part of the “managed” population, and are not included
in this total.
the water temperature drifts up to approximately 24.5
C over the course of 24 hours in relation to the
ambient temperature of the building in which the animals are housed.
While the building is kept at a relatively constant temperature, strict regulation of the
building’s interior is not possible. Thus, the Day House experiences general temperature trends that
correspond to outside conditions and seasons of the calendar year. Ambient temperatures in the
building have generally ranged between 23
C (January/February) and 30
Shinisaurus are semi-aquatic predators that generally feed on fish, tadpoles, aquatic insects
and larvae in the wild (Huang et al. 2008) with remains of terrestrial arthropods, winged insects, and
crustaceans also discovered in the examined guts of specimens originating from the Yen Tu nature
reserve in Northern Vietnam (Ziegler et al. 2008). At WPZ, young Shinisaurus are fed a few days after
being born and eat a greater variety of foods (crickets, mealworms) than the adults, with the majority
of the diet consisting of earthworms (Lumbricus spp.). Though redworms used for composting (Eisenia
foetida) and tubifex worms (Tubifex tubifex) have been offered in the past, WPZ has had greater
success by feeding earthworms collected from zoo grounds – usually found by searching through piles
of leaf litter. Juveniles are offered purchased, cultivated earthworms and small pieces of pink
(newborn) mice after a few weeks. WPZ adults are fed and cleaned on alternating days, and are fed
earthworms (Lumbricus spp.) and pink mice. Each adult receives one pink mouse a week if not being
fed for weight gain. Crickets, giant mealworms (Zoophobis spp.), mealworms (Tenebrio molitor), and
goldfish have also been offered in the past, with limited success. Food is offered on a regular basis
even when animals predictably stop eating from approximately October to February.
Shinisaurus weights are taken weekly to monitor growth rates in juveniles and seasonal
fluctuations in adult weights. The young have average monthly increases in mass of 20-35% during
their first year with appetites leveling off at around ten months of age.
Shinisaurus are viviparous, generally giving birth to litters of 1-9 fully developed offspring,
with captive females able to breed annually (Langerwerf 2008). WPZ Shinisaurus are paired in
February following a relatively dormant winter period where animals usually stop eating but still
remain somewhat active. Pregnant females steadily gain weight and tend to bask more than usual
until 5-8 weeks prior to giving birth when food consumption ceases and the abdomen becomes very
taut. During the period prior to parturition females lose approximately 5-8% of their mass as well as
their distended appearance. The male and female are separated at around eight months into the 8.5-9
month gestation historically exhibited by WPZ’s breeding females. Past WPZ births have resulted in
females losing 25-35% of their mass, and 11 litters over the past 15 years have produced 59 total
individuals, with litter sizes ranging from 1-9 and averaging 5.6 offspring per litter. Small litters are
usually accompanied by the passing of infertile ova. Dates of parturition across 11 litters have ranged
from 14 September to 17 December, with an average date of 25 October.
Wild populations of Shinisaurus inhabit mountain ranges with elevations ranging from 500-
1200 m above sea level and temperatures spanning -5.6-39.5
C (Huang et al. 2008), and temperature
recommendations from captive breeders have referred to populations housed entirely outside or with
access to outside areas in locations such as Alabama, USA (Langerwerf 2008). However, WPZ’s
collection is housed entirely indoors, in conditions that are arguably milder than what the animals
might experience in the wild or in outdoor breeding enclosures.
Despite experiencing light cycles that are set to correspond to a latitude of 23
(a latitude at
which Shinisaurus may be found in the wild), WPZ’s collection consistently breed in February/March
and give birth In October/November, demonstrating a periodization that differs from cycles exhibited
by wild Shinisaurus that typically breed in July and August (Huang et al. 2008), and exhibit parturition
in April or May (Langerwerf 2008). Given the predictable temperature fluctuations observed inside
the Day House building in response to outside weather conditions, and the WPZ Shinisaurus
collection’s tendency to follow the same activity cycles from one calendar year to the next, it is possible
the WPZ collection may be responding to cues related to seasonal fluctuations in outside temperature
or humidity. Hofmann (2000) observed mating in the early spring among his captive collection,
although unlike WPZ’s husbandry practices, the Shinisaurus in his collection were maintained at 16
throughout a dormant period from October to mid-April.
In captivity, variation in Shinisaurus gestation periods may be attributed in part to differences
in the practice of cooling or hibernating lizards. Hofmann (2000) states that a gradual cooling down to
temperatures of 16
C for three to four months is essential for successful breeding in captivity, while
Langerwerf (2008) describes a one year gestation in his captive colony which includes 5-6 months of
hibernation. As Woodland Park Zoo’s Shinisaurus collection does not go through a period of true
hibernation, it is interesting to note that the gestational length of WPZ’s collection, at an average of 8-9
months, is not significantly different than that which is recorded for wild populations.
Hofmann (2000) has also indicated that individuals in his collection became sexually mature
within 2-3 years. However, WPZ’s collection records document a successful mating occurring in a 15
month-old female, and a recent birth has indicated breeding and sexual maturity in individuals as
young as 13 months of age. It is possible mild indoor temperatures, absence of hibernation, and
accelerated growth rates as a result of greater food availability or nutrition may contribute to earlier
sexual maturity, though further investigation is warranted.
It is likely that variations in housing conditions and husbandry parameters affect Shinisaurus
life cycles, growth rates, and time to fertility. In continuing to gather data on the temperature,
humidity, growth rates, and breeding statistics of WPZ’s collection and by comparing these data with
other institutions, we hope to better understand Shinisaurus husbandry requirements and to modify
practices to create ideal breeding conditions for our facility. It is also our hope that documentation of
WPZ’s collection, housed completely indoors, may contribute valuable information toward captive
breeding attempts in other geographic areas where it is not feasible or practical to provide outdoor
WPZ will continue to breed selected pairs of Shinisaurus crocodilurus according to the plan
recommended by the North American Regional Studbook and the Association of Zoos and Aquariums
(AZA) Species Survival Plan (SSP).
Thank you to the Guangxi Forestry Bureau and Daguishan Nature Reserve and Key Lab of
Endangered Animal Ecology for hosting the “Daguishan International Symposium on Protection and
Breeding of Shinisaurus” and for inviting us to participate. We would also like to thank the Woodland
Park Zoo and the University of Washington School of Forest Resources for their support of this
Additionally we would like to thank Peter Miller, Alicia Pike, and the Woodland Park Zoo Day
House staff and volunteers for their hard work and contribution to this project, Dr. Jennifer Pramuk,
Tina Mullett, Deanna Ramirez, Diane Uyeda, Dr. Aaron Wirsing, and the UW Predator Ecology Lab for
their thoughtful feedback, Frank and Kate Slavens, and Dr. Zhengjun Wu for generously providing
valuable information on this species.
Fresno Chaffee Zoo, 2007. North American Regional Studbook Chinese Crocodile Lizard
(Shinisaurus crocodilurus). 64 pp.
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Breeding. Reptiles Magazine 8(4).
Huang, C. M., et al. 2008. Population and conservation strategies for the Chinese crocodile lizard
(Shinisaurus crocodilurus) in China. Animal Biodiversity and Conservation 31(2):63-70.
Langerwerf, Bert. 2008. Shinisaurus Secrets. Reptiles 16(4):40-46.
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Supplement to the April 2008 REPTILES magazine article “Shinisaurus Secrets”.
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1930) from Vietnam and China. The Raffles Bulletin of Zoology 56(1):181-187.