By Jerry G. Walls
I have some crocodile skinks. What can you tell me about keeping and breeding them?
Crocodile skinks (Tribolonotus gracilis) are distinctive and fascinating lizards. They also are relatively easy to keep. Their heavily keeled scales and bright-orange eye rings never fail to attract attention. They lead a primarily diurnal existence but still prefer low-light conditions and cool temperatures, with lots of hiding places on the terrarium floor.
A typical setup consists of keeping a pair in a 20- to 25-gallon aquarium or plastic tub with a screen lid that supports a full-spectrum fluorescent light and a weak (50 watts or less) basking light. Keep the temperature 75 to 80 degrees Fahrenheit during the day; it can drop about 10 degrees at night. Crocodile skinks don’t need branches or plants, but they do like to swim and will dehydrate rapidly if kept too dry. A fairly humid, deep mixture of potting soil and sphagnum moss is a good substrate. Provide a shallow water container too.
Crickets and mealworms can be the staple diet. Vary this with earthworms, spiders, small beetles, moths, caterpillars and even small guppies and mosquitofish placed in the water bowl.
Adults are sexually mature when about 1 year old and roughly 6 to 7 inches in total length. Another distinctive trait is the presence of small pores (called volar pores) under the feet. These are thought to secrete scents that are used to recognize another skink’s sex and possibly to mark territory. Though both sexes have pores under the palms of the front feet, only mature males have areas of enlarged scales and pores under the bases of the third and fourth toes of the hind feet. (The first toe is the short one on the inside of the foot.) If you use a magnifying lens to examine the hind feet of your specimens, you should be able to tell which one is the mature male.
Successful mating and egg laying have occurred simply by housing an adult male with an adult female. A good cage environment includes plenty of hiding places on the cage floor (such as leaf litter and pieces of cork bark), a varied diet offered at least every other day (with a few crickets always available) and a nestbox for the female. The nestbox can be a 6- by 12-inch pan about 2 inches deep, filled with damp (not wet) sphagnum moss or a similar substrate and covered with a piece of bark.
These are very secretive skinks that seldom leave their hiding places. A mated pair tends to share the same hiding spot, and a gravid female will begin to look a bit pudgy. It is not certain how many days elapse between mating and laying of the first egg. Typically, once the first egg is laid others will be produced at roughly 65- to 70-day intervals. Only one egg is laid at a time. Incubation takes roughly 70 days, so a new egg is laid at about the same time the previous egg is hatching.
If you find an egg in the nestbox, you can leave it there (be sure the moss stays moist) or move it to an incubator containing damp vermiculite (water-to-vermiculite ratio is 1-1 by weight). Keep the incubator temperature near 80 degrees during incubation. Hatchlings look much like the adults and are typically 21/2 inches long. They’ll feed on small crickets and mealworms within a few days of hatching. Be sure that their terrarium stays humid and that you provide them with enough food at all times. Dust the food with a calcium-vitamin D3 supplement at least three times a week.
With any luck, a captive-bred crocodile skink should live at least a decade, but they really haven’t been in the hobby long enough to know if they will live much longer than this.
Keep your ears open for the low yelping and squeaking noises made by crocodile skinks — even hatchlings may vocalize. This behavior is very unusual among lizards other than geckos.