Prehensile-tailed Skink (Photo by G. O'Neill)

I (Dr. Wright) first saw a picture of a prehensile-tailed skink (Corucia zebrata) when I was 12 years old. The old black and white photo of it hanging by its tail from a branch, slightly coiled back on itself, with an inscrutable expression of reptilian languor -- it left an indelible impression.
Years later I had the chance to keep a couple of pairs. I grew to love them, as they begged for food, climbed around their enclosures and dangled nonchalantly by a single leg from a branch, staring at me if I was doing anything in the vicinity. At about the same time I began my residency in zoological medicine at the Philadelphia Zoo, which then had the largest captive collection of prehensile-tailed skinks in the world. That was the first time I was exposed to the wide variation in size, scalation, color, pattern and personality of this incredible lizard.

More Than One Species?

Corucia zebrata is the world’s largest extant skink. Some specimens reach about 3 feet total length and weigh about 2 pounds. Others may only be a little over 2 feet long and weigh no more than 1 pound.

This variation in size was one of the first things that caught my attention and made me seriously consider the possibility that this megaskink might represent a similar sort of evolutionary bush as the giant tortoises of the Galapagos Islands, with several species or subspecies waiting to be described. The variation in color and pattern also seemed to support the possibility of multiple taxa of prehensile-tailed skinks.

Some of the color variations of prehensile-tailed skinks (G. O'Neill)

The overall background color was typically a pale green, ranging from a spring green to a deep olive green. Many had zig-zag bands of brown or gold crossing their backs while a few instead had only dapplings of black or brown spots. Some had small, cream-colored scales scattered over their bodies, others had black edges to their scales. The bellies ranged from a deep cream to yellow color, or were the same background green as the back. The big scale over the nose varied in color from white to green, deep brown or black. The irises of the eyes could be gold, green or brown.

It seemed consistent that certain sizes of skinks were certain colors and patterns with most of the largest ones being the “dalmation” pattern of a pale green lizard with black spots. Was it possible that the different forms of prehensile-tailed skinks actually corresponded to the different islands that they inhabited? The literature was sparse and inconclusive on this matter.
I once hired Michael Balsai for the Roger Conant Fellowship in Herpetology at The Philadelphia Zoo to study this question. One aspect of his work was a comprehensive review of museum specimens with locality data Ñ and he found some subtle morphological differences that seemed to correlate with geographic localities, but not enough to be conclusive either way. Because some of the obvious morphological variations of live specimens, such as iris and skin color, that were faded in these preserved specimens, some features that would be useful in an analysis were unavailable for this study.

Joyce at the Philadelphia Zoo with a prehensile-tailed skink on display (G. O'Neill)

A study by the curator who preceded me at the Philadelphia Zoo analyzed the breeding success of the prehensile-tailed skink program that had been going on for about 20 years at the time. There were some curious patterns of reproductive failures with certain pairs of adults. These resulted in either a lack of babies produced or babies dying very soon after birth. An analysis of additional years of breeding data by Michael Balsai, Brint Spencer (the curator after me) and R. Scott Winters refined the observations.

There seemed to be a correlation that when a pair produced a dead baby from their first mating, they were more likely to continue to produce more babies that died than lived. If a male and female produced a baby that thrived, they were much more likely to produce thriving babies in the future. Among other explanations, such as variation in the health of the parents and microhabitat differences between enclosures, these findings suggest that there might be some genetic differences between certain skinks that will result in infertility or weak babies.
More work is needed to elucidate the underlying factors but certainly one arm of the research should be to determine if there is an underlying significant genetic difference between populations of prehensile-tailed skinks to determine if there are “undiscovered” species or subspecies.

A brief expedition to the Solomon Islands to further investigate the question of undiscovered taxa of Corucia was inconclusive but suggests they may occur on additional islands than previously known. A longer expedition to focus on acquiring DNA and morphometric data from specific locales is warranted though it also may be inconclusive, especially if skinks have been moved from island to island by humans and thereby obscuring the real distributions.
It would be interesting to find out for certain if there are other taxa or if Corucia zebrata is simply an incredibly variable species throughout its island habitats.

Enclosure Design

The cage needs to accommodate the arboreal tendencies of these lizards. An adult trio will do well in an enclosure that’s approximately 5 feet tall by 3 feet wide by 3 feet long. It should be well furnished with many climbing opportunities on all sides. Round cork tubes are excellent hiding spots and can be secured at different heights on the walls of the enclosure. Flat pieces of cork should also be left on the bottom because some prehensile-tailed skinks spend a lot of time on the ground. Sturdy branches, about 1 to 5 inches in diameter, should be securely placed so they can’t be shifted. These branches should allow the skinks to climb from the floor all the way to the top of the enclosure.

Prehensile-tailed skinks at home with a hollow log (G. O'Neill)

Because prehensile-tailed skinks originate from wet, tropical habitat their enclosure should have a high humidity, ranging from 70 to 90 percent over the course of a week. A misting system or rain system may be used and could stimulate activity. Sphagnum moss or cypress mulch are good substrates for moisture retention when used with a misting system, but are difficult to incorporate into a rain system.

Good ventilation is important with such high humidity to prevent mold and fungi from growing in the cage. A vent system at the top of the enclosure and one near the floor will allow passive air circulation. This can be enhanced by placing a small fan at the top of the enclosure to draw air out of the vents.

Although prehensile-tailed skinks are most active at dawn and dusk, they will often come out and bask during the day. An ultraviolet-B-rich source of light should be provided for several hours a day along with enough basking spots so each skink can get some UVB and thermoregulate without having to share its perch with another skink. An ambient temperature fluctuating between 78 and 85 degrees Fahrenheit is good as long as there are daytime basking spots of 95 to 100 degrees available. Night-time basking spots provided by radiant ceramic heaters or red or dark blue incandescent bulbs are suggested, especially for gravid skinks. Because the skinks are active at night, a small amount of visible light, replicating moonlight, should be provided too.

Diet

Prehensile-tailed skinks are herbivorous. Their diet should be primarily dark green, leafy vegetables such as romaine, escarole, kale, spinach, greens (collard, turnip, mustard, dandelion) and cilantro. Other dark green leafy produce varieties are seasonally available and can be rotated.

Some skinks will be reluctant to try new foods but will accept them if a small amount of sweet potato baby food is spread onto them.

Supplementation with calcium and trace minerals and multivitamins are important. A salad mix should be offered every one to three days. I recommend using a multivitamin supplement once a week and a calcium and trace mineral blend on the other salads.

Breeding and Parental Care

If you plan on breeding prehensile-tailed skinks it is important to start off with animals that appear similar in size and color pattern in order to have the best possibility of success. If you are buying them over the Internet, therefore, ask for close-up photos of the eyes and nose, as well as pictures of the back and belly, to know what you are getting.

Baby and juvenile prehensile-tailed skinks often look different than the adults, so photos of the male and female should be evaluated if you are purchasing young specimens. Unfortunately, some skinks that appear similar in appearance still may be infertile or produce babies that fail to thrive.

Your skinks must be correctly sexed. Enough female skinks have the broad head and prominent jowls of male skinks and enough male skinks look like female skinks to make it worthwhile to have a veterinarian properly sex your skinks.

Sexing is a simple process. The skink is anesthetized with a rapid-acting inhaled anesthetic such as sevoflurane, and the genitals are everted (popped). This cannot be done consistently on a conscious male skink without the risk of damaging the hemipenes, and if you rely solely on external characteristics to sex your skinks, you may spend years with same-sex pairs and no success! Female-female pairs may even lay infertile slugs in the cage mimicking a male-female pair that isn’t compatible. So sexing by a vet is recommended. Sexed pairs or trios of one male and two females work well together.

Not all skinks get along, so watch carefully during the initial months after putting a group together. A “howdy box” can be placed into an enclosure and used to introduce a skink to other skinks. This is basically a smaller cage that can be placed into the main cage and which allows the skinks to observe each other without coming into contact. This will help you assess if there is going to be a dangerous level of aggression while protecting the skinks from attacks. If the skinks ignore each other after a few days, open the howdy box so they can interact without barriers.

Minor aggression often occurs as the skinks work out a dominance hierarchy. This isn’t necessarily a problem, but if attacks are relentless and bites leave open wounds or damage to toes or tails, or if the lizards bite down and hold onto each other for a long time, you likely have put together an incompatible pair or trio.

Breeding is a secretive affair in captivity, and many prehensile-tailed skinks will stop copulation if they detect any motion outside the cage. It takes place throughout the year and there doesn’t seem to be much of a correlation with changing husbandry parameters such as temperature or humidity. If you have a compatible pair, provide good husbandry, and feed a balanced diet, then breeding should happen.

Corucia zebrata is a livebearer, and a compatible pair of skinks will produce a single baby or twins every nine to 18 months. Because some skinks have given birth six to seven months apart, it appears that the gestation period is at least six months. Most females do not immediately rebreed after giving birth, hence the range of interbirth intervals.

Mom and newborn (photo by K. Wright)

The babies are large. A single baby is about the equivalent of a human giving birth to a first grader! Twins are typically smaller than a singleton, but their combined weight may be much more.

Twins (Photo by K. Wright)

As mentioned previously, some pairs of skinks seem unable to produce healthy babies. If more than one baby is born dead or dies within its first month, try to find different mates for each member of the pair.

Baby prehensile-tailed skinks should be left with their family group. The adults will guard the babies, and maybe push them over to the food plate. Although the parents seem to be the most protective, even unrelated adult skinks will come to the aid of a baby.

Babies often nibble on the feces of adult skinks, a process that may help seed their gastrointestinal tract with the microorganisms needed for proper digestion of plant material.
A family group of skinks may be kept together for more than a year before the adults begin to exhibit dominance behavior toward the younger skinks. Once the juveniles are on the receiving end of dominant or aggressive behavior from the adults, it is time to set them up into a group of their own.

Juvenile groups often exhibit quite a bit of conflict before a hierarchy develops. I do not recommend separating babies from their family until they are at least 1 year old or so. I believe this “family time” allows them the opportunity to learn how to get along with other skinks and reduces the chance of inappropriate aggression when paired with other skinks. Thus, even though babies are available, think twice before taking ones that are removed from their family group before they are a year old.

Concern About the Future

I worry that prehensile-tailed skinks may go extinct, as happened with the large Cape Verde skink (Macroscincus coctei). The Solomon Islands government is always looking for ways to improve the economy. Unfortunately, many of the ways that are offered are at the expense of the natural resources that are vital to the survival of the prehensile-tailed skink. For example, the forests of the Solomon Islands were considered unloggable up until the early 1990s. Technology changed and vast tracts of forests, home to prehensile-tailed skinks, are now open to timber companies. Other countries are considering using the Solomon Islands as dumping grounds for hazardous waste.

Until some of the questions about the taxonomy and natural history of the prehensile-tailed skink are answered, it is unlikely that any significant conservation efforts are headed their way. The only skinks that may survive past the next few decades may be in captivity. If you have a prehensile-tailed skink, not only do you have a fascinating pet, but you may be holding an essential link to the future of these wonderful lizards.

I would like to thank Joyce Parker, Keeper Foreman at the Philadelphia Zoo, for all her years of being a wonderful care-giver to a large colony of prehensile-tailed skinks, and to Greg O'Neil, a former keeper at the same zoo, who provided many of the photos for this article.

This article originally appeared in Reptiles magazine.

The Corucia Conservatory

I have taken over the Corucia Conservatory started by Dr. Susan Donaghue several years ago.  This project involves getting together a large group of skinks for research into their behavior, nutritional needs, breeding, and genetics with an ultimate goal of providing information to better their lives in captivity and stimulate conservation efforts for this species.  Prehensile-tailed skinks have been a part of my life for over 20 years and I hope to continue to make advances in our knowledge as I have done in the past with articles on the hematology, diseases, and captive care, and to stimulate future fieldwork to better understand this species in the wild.

If you have prehensile-tailed skinks that are not in breeding situations or you are looking for a home, I encourage you to consider donating your pets to the Corucia Conservatory.  You may contact me at info@azeah.com for more information.

Sincerely,

Kevin Wright, DVM

Some of my publications:

Wright K.M. 1993. "Captive Husbandry of the Solomon Island Prehensile-tailed Skink Corucia zebrata." Bulletin of the Association of Reptilian and Amphibian Veterinarians 3(1): 18-21.

Wright K.M. 1993. "Medical Management of the Solomon Island Prehensile-tailed Skink Corucia zebrata." Bulletin of the Association of Reptilian and Amphibian Veterinarians 3(1): 9-17.

Wright K.M. and Skeba S.J. 1992. "Hematology and Plasma Chemistries of Captive Prehensile-tailed Skinks Corucia zebrata." Journal of Zoo and Wildlife Medicine 23(4): 429-432.

Wright, K.M. 1996. "Taxon management account, Solomon Island prehensile-tailed skink Corucia zebrata", in Hammack, S.H. (Ed.): American Zoo and Aquarium Association Lizard Advisory Group Taxon Management Accounts, Vol. 1. Fort Worth Zoological Park, Fort Worth, TX.

Wright, K.M. 1996. "Medical Management of the Prehensile-tailed Skink Corucia zebrata", Proceedings of the San Diego Veterinary Medical Association Annual Conference, pp. 34-36.

Wright, K.M. 1995. "Care and Management of the Prehensile-tailed Skink", Proceedings of the Third Biannual Special Species Symposium at the Cornell University College of Veterinary Medicine, pages not numbered.

Wright K.M. 1995. "Medical Management of the Prehensile-tailed Skink", Proceedings of the 1995 North American Veterinary Conference, pp. 664-665.

Wright, K.M. 1991. "The Solomon Island Skink: Corucia zebrata." Reptile and Amphibian Magazine. Mar/Apr 1991, pp 10-19.

Copyright 2008
Kevin Wright
Arizona Exotic Animal Hospital, LLC
744 N Center Street
Mesa, AZ 85203
info@azeah.com