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LINKS
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A slightly different version of this paper was published in The Cold Blooded News,
the newsletter of the Colorado Herpetological Society, Vol 23, #9, September, 1996.
I was recently compiling alist of all the species of lizards native to the state of Colorado, when it suddenly occurred to me that I had had personal experience in collecting and keeping the majority of them. Thinking that others might benefit from my experiences, I decided to offer the following commentary.
General Husbandry:
All of Colorado's lizards are relatively small and primarily insect eaters, and should be offered as wide a variety of food as possible. Collared and Leopard lizards are known to eat other prey, including smaller lizards, and should occasionally be offered live pinky mice. When feeding domestic crickets, wax worms, or mealworms, dusting food with a vitamin-enriched calcium powder is recommended.
Most native lizards occur where large numbers of grasshoppers are found during the summer months, and these seem to be a staple of many lizard's diets. Miller moths also make an easily collected and nourishing food. Wild-caught lizards that do not accept a variety of domestic insects should not be kept through the winter months, when wild insects are not available.
All Colorado lizards except the two species of skinks are diurnal basking lizards, and should be provided with a basking light and an ultra-violet bulb. A 15W 18" [45.7 cm] black light, not a Vita-Light, and a 40 to 60W incandescent bulb are satisfactory for a 10 to 20 gallon aquarium or an equivalent sized cage (about 12" [30 cm] high).
Again with the exception of skinks, sand or fine gravel is a suitable substrate. A basking rock or two should be provided. For lizards that bury themselves, I have found that a fine quartz sand, available at many building supply stores, is a good choice. For a coarser substrate, I have used anything from sand-blasting sand to pea gravel (available at landscaping outlets). Aquarium gravels, as sold at tropical fish stores, are now generally epoxy coated, to prevent toxicity to aquatic animals. They should be easy to wash and recycle, but are expensive enough that I have never used them (even in my tropical fish tanks). When housing lizards that like to dig burrows, care should be taken that the basking rock sit securely on the bottom of the enclosure, so that
it won't collapse onto a lizard trying to burrow under it.
Skinks may be housed on a substrate of sand covered with dried leaves, garden mulch, or sphagnum moss. They probably require neither a basking light nor U.V., but should be provided with a source of heat (a radiant heating element or an under-glass aquarium heating pad) if the room in which they are kept is allowed to cool below about 72°F [22°C].
Colorado is an arid place, and water in the wild can be a scarce commodity. However, with the possible exception of Collared and Leopard lizards, Colorado native lizards should be provided with a shallow dish of fresh water at all times. Many Collared and Leopard lizards never seem to drink water from a dish; they should be offered water once or twice a week by misting one side of their enclosure, or, if the lizards have been tamed, they may be offered water directly from an eye dropper or syringe, applying one drop at a time to its lips. If the lizard is interested, it will lap avidly from whichever source; if not, it will turn away or attempt to 'dry' its mouth on the substrate. If a lizard refuses water part of the time, there is no need for concern. (If a lizard NEVER refuses to drink, it probably isn't being offered water often enough.) As long as the lizard's tail is firm and round and the animal appears well fleshed, it is probably getting enough water.
When collecting lizards for captivity, it should be remembered that adult lizards generally fare better than juveniles, which are much harder to feed and are generally much more temperamental than adult specimens. When attempting to keep juvenile lizards, calcium supplementation of food sources is doubly important, as is the availability of strong ultraviolet light. Juvenile lizards in the wild tend to remain active much later in the season, when the climate can be more extreme and generally dryer, than do adult lizards.
Hibernation and Breeding:
I have never hibernated lizards. This is partly because there is no place in my house that maintains a suitable temperature for hibernation (around 55°F [13°C]) during the winter months, but also because I have no great burning desire to breed my lizards. (Hibernation is said to be essential in breeding to synchronize the breeding cycle.) Not hibernating reptiles may shorten their total life expectancies somewhat, because they are active all year around instead of 8 to 10 months (or 4 to 6 months in the wild), but otherwise seems to have no adverse affect.
Another reason for not hibernating some of the animals that I have caught is that they are destined to live in a school classroom, where activity during the winter months, when school is in session, is their sole purpose. (Zookeepers at the Denver Zoo have told me that they generally do not hibernate reptiles for similar reasons, unless breeding is desired.)
Breeding habits of many Colorado lizards in the wild is poorly known (Hammerson, 1986), and I have little information to add on the subject. Except for Collared Lizards, I know of no one who has attempted to breed any Colorado native lizard.
Colorado Native Lizards by Species:
Family Crotaphytidae
- 1. Collared Lizard (Crotaphytus collaris)
- This is the only Colorado native lizard that I know of having been bred in captivity; at least two members of the Colorado Herpetological Society have successfully raised hatchlings, and one of them (Scott Patterson) breeds them regularly. I have never captured a Collared lizard in Colorado (I have caught them in California), but I do have two half-grown captive-bred juveniles (over one year old) from Colorado native parents.
Once they are tamed down, Collared lizards make delightful pets, offering no resistance to being picked up and readily accepting food from one's fingers. When wild or not handled
frequently, they are prone to bite, and can cause painful experiences. Juveniles and breeding females in particular need lots of calcium supplement in their diet. When my babies contracted a respiratory infection, I took them to a veterinarian that specializes in exotic animals. In addition to treating their infection, he advised me that many of the commercial calcium preparations contained an excess of vitamins A and D, which can build up to toxic levels if over-administered. He prescribed a liquid calcium supplement, which I faithfully administered orally once a day for about a month. The lizards began to exhibit a deterioration in muscular control, a "twitchiness" of the hind legs, and ultimately lost the ability to control their walking. On returning them to the vitamin-enriched calcium powder (I am using Formula C/P by Mardel Labs), they exhibited an immediate recovery.
Collared lizards normally inhabit rocky areas, but are known to venture out into open plateaus or canyon bottoms with firm soil, where they can run bipedally at rather remarkable speeds. In captivity, they should be provided a fairly large enclosure with coarse sand or gravel substrate. A large rock or rock pile should be available for them to bask on. They will retreat into a hide box at night if one is available; otherwise they will attempt to burrow under rocks or into the corners of their cage. They are not particularly strong jumpers for their size; 18" [45cm] or less from the top of their rock pile to the top of the enclosure is sufficient to keep them contained. They do well on a diet of calcium-dusted crickets but will benefit from an occasional pinky mouse or smaller lizard.
- 2. Longnosed Leopard Lizard (Gambelia wislizenii)
- I have captured these lizards in California, but never in Colorado. The last time I kept one in captivity was long enough ago that my recollections are imprecise. I have, however, known
others who have had good luck keeping them. Much of what was said about Collared lizards above is applicable to Leopard lizards as well. They too have a rather nasty bite.
Leopard lizards may be somewhat more likely to eat smaller lizards than are Collared lizards, and a dietary supplement of pinky mice or smaller lizards should be offered regularly.
Family Phrynosomatidae
- 3. Lesser Earless Lizard (Holbrookia maculata)
- I have captured two of these charming little lizards, taken them home, and attempted to provide for them. One would accept mealworms (which I don't consider an adequate diet by themselves) but was unwilling to eat small crickets. The other refused both mealworms and crickets. Both were released back to the same location in which they were found.
Earless lizards inhabit sandy areas throughout the eastern plains of Colorado, in areas which normally abound with grasshoppers, which I suspect provide the bulk of their diet.
They are the least wary, and hence the easiest to catch by noose, of any lizard I have ever chased.
I would very much like to find a method for keeping this species in captivity, but don't relish the thought of having them starve as soon as grasshoppers are no longer available. If anyone finds a way to keep them successfully in captivity, I would like to hear about it.
- 4. Texas Horned Lizard (Phrynosoma cornutum)
5. Short-Horned Lizard (Phrynosoma hernandesi)
- I have never captured either of these two species in the wild, although I believe that in my youth I purchased some Texas Horned Lizards in a California pet store. I have, however, had considerable experience, none of it with any degree of success, in keeping other species of horned lizards. I believe that the same general observations apply to all species.
Ants are the primary food source for most, if not all, horned lizards. While captive specimens can initially be enticed to eat other food (especially mealworms), my experience is that they will soon languish, refusing food altogether, and die. Unless a year-around supply of ants can be assured (and I am not certain that just any species of ants will suffice), I do not recommend keeping these lizards in captivity.
- 6. Eastern Fence Lizard (Sceloporus undulatus)
- Only once have I captured a pair of lizards of this species, but those individuals lived happily in a school classroom for an entire year, and made most satisfactory school "pets." They are alert and attentive lizards and tame down well, accepting human proximity without panicking, and may even be enticed to accept food from fingers. Wild individuals are prone to bite, but they are small enough that it is not painful, and they usually let go quickly.
Eastern fence lizards are adroit climbers, and should be provided a pile of medium sized rocks onto which they can climb to bask, and under which they can seek shade. They are also adept at burying themselves in sand, particularly at night, and should be provided a substrate of fine-grained sand in which they can hide. They are good jumpers, and will spend considerable time hanging upside down on a screen top under their basking light. A screen top with a sliding door is highly recommended if the top of their enclosure is less than 8" or 9" [~20 cm] from the top of the highest rock.
Like all members of Genus Sceloporus, their sharp, overlapping scales provide a ready refuge for ticks, particularly the large red-orange variety. Ticks breed quickly, and a heavy infestation can weaken a lizard to such an extent that they languish and die. I have never used any of the various insecticide treatments for reptiles, but have successfully controlled (although never eliminated) tick infestations by regularly picking or scraping them off each lizard onto a smooth, hard surface where they can be crushed with fingernails.
- 7. Desert Spiny Lizard (Sceloporus magister)
- I have never collected this species in Colorado, but I have had considerable experience, and success, with the species from the deserts of California. They are probably the largest (if not longest) and heaviest-bodied lizard found in Colorado, and can have a quite painful bite, but they have proven to be among the most satisfactory lizards I have ever kept. Mine would run up to the door of their cage whenever I approached and readily took food from my fingers.
Desert spiny lizards are generally found in rocky areas and are exceedingly wary, often seeking cover when one approaches within 20 or 30 feet [6 - 9 m]. They also climb trees; in California they are commonly found in Joshua trees, often 10' [3 m] or more from the ground. If they are successfully approached, they show no fear of a noose, but will often bite at it, much to the frustration of the intrepid collector.
They are less inclined to bury themselves in sand than eastern fence lizards, but will seek refuge in a rodent burrow or a crevasse in the rocks. A large, tall habitat should be provided for these active lizards, with a coarse sand or fine gravel substrate, and a large pile of rocks to bask on or hide in under. They are good jumpers, and a secure cover should be provided.
- 8. Sagebrush Lizard (Sceloporus graciosus)
- I have never caught nor kept this lizard, nor to my knowledge have I ever seen one. However, based on experiences with other closely related species (Western and Eastern Fence
lizards), I would expect that it would prove satisfactory for captive husbandry.
- 9. Tree Lizard (Urosaurus ornatus)
- My only experiences with this intriguing lizard involve two specimens. The first I caught many years ago in a rocky canyon in Arizona, and my recollections of its time in captivity are hazy at best. The second specimen I "rescued" from a pet store in Colorado. It had been kept in a cage without a heat or light source, and was badly undernourished when I acquired it. Fortunately, this occurred during the early summer, so I was able to fatten it up quite satisfactorily on a steady diet of miller moths. It did quite well for the better part of a year, spending most of its time upside down on the screen lid of its cage (a 10 gallon aquarium), becoming tame enough not to panic when I approached its cage, but never taming as much as other species I have kept. It subsequently succumbed to a bacterial eye infection.
These are agile lizards, with incredible leaping ability (8" [20 cm] or more straight vertical from a standing start); if kept in an aquarium with a screen top, a sliding door in the screen is essential. A coarse sand or gravel substrate with large twigs or small branches (limbs at least equal to their body diameter) for them to climb on and get closer to the heat source provide a good habitat. A pile of palm-sized or larger rocks that they can climb on or under are also satisfactory.
- 10. Side-Blotched Lizard (Uta stansburiana)
- Small but lovely, alert and attentive, these brightly colored lizards are among the most satisfactory and endearing of all the creatures I have collected. I have never collected them on the western slopes of Colorado, but individuals caught as adults in California have thrived to delight, both at home and in the classroom, for about two years average.
They are easily caught, and are fond of perching on top of small rocks to bask, but never seem to seek refuge in rock crevasses, rather dashing into the cover of bushes nearby. In captivity, they prefer to bury themselves at night in fine sand, which should be provided as a substrate. A small basking rock will be much appreciated.
I have never known them to be finicky eaters, readily accepting mealworms, crickets, and a variety of "wild-caught" insect and other arthropod life, including spiders and daddy long-legs. My friend and I spent an amusing evening watching one try to eat a pill bug (a common garden isopod crustacean); every time the lizard tried to bite it, the pill bug rolled into a tight ball and stopped moving, at which point it effectively "disappeared" from the lizard's vision.
Family Scincidae
- 11. Many-lined Skink (Eumeces multivirgatus)
12. Great Plains Skink (Eumeces obsoletus)
- I have not collected, kept, nor even seen either of these two species of lizards. However, I have heard that skinks in general make very satisfactory, if somewhat shy and reclusive, pets. To the best of my knowledge, skinks do not come out to bask in the sun, being perfectly content at the lower temperature found in the litter and under the brush which they inhabit. The inference therefore is that in captivity they should not require either a heat lamp or an ultraviolet light, provided that their enclosure is kept at a suitable temperature for normal metabolic activity (most likely between 72° and 80°F [22° - 27°C]). I have found that a sand substrate covered with a thick layer of garden mulch, leaf litter, or moss provides a suitable habitat for those reptiles of similar habits that I have known.
Family Teiidae
Whiptail lizards (Genus Cnemidophorus) are said to have the largest brain to body mass ratio of any cold-blooded vertebrates. This implies that they are the most intelligent of all reptiles (and anyone who has tried to capture these elusive and devious lizards will readily agree with that assessment). They spend very little time simply lying in the sun to bask, rather thermoregulating by varying the amount of time they spend hunting in the direct sun rather than in the shade beneath bushes. At night and during the heat of midday they take refuge in burrows, abandoned rodent burrows if available, although they are fully capable of digging their own. At night they close off their burrow by shovelling loose sand into the mouth using their front
feet.
In captivity, they should be provided with a fine sand substrate, a basking rock buried so it rests firmly on the bottom of the enclosure, lest it fall on them when they try to dig under it, and a hide box with a small enough opening (1" X 1" [2.5 X 2.5 cm] or so) that they can close it off with sand at night. I use the black plastic tray from a frozen dinner entre (about 4" X 6" by 1" deep), with a 1" door cut into one end, buried in the sand at the end of the cage farthest from the heat lamp.
- 13. Six-lined Racerunner (Cnemidophorus sexlineatus)
- I'm still collecting data on this species. I caught four of these lizards in the sand hills of northeastern Colorado during July and August of 1995 (2 individuals each on 2 trips). Two from one trip spent an entire year in a school classroom; the other two lived at my home. At no time after they were caught were the two pair together, to allow the spread of contagion, yet all four died within a few weeks of each other early the next summer, with what appeared to be the same symptoms. In 1996, I only collected one new individual, which met with a similar fate at about the same time the following year.
What I find curious about this lizard is that when collecting them, all the individuals I observed were exactly the same size. Ordinarily in a typical wild population, lizards will be found of different size and ages, most species of lizards not reaching their full adult size in the first year. (See comments on the Western Whiptail, below.) This lack of size variation leads me to wonder if the normal life expectancy of this species is less than two years, and if last year's captives simply died of old age. I only regret that I was unable to afford a veterinarian's bill at the time they became ill.
The 1995 captives, for the year they survived, became incredibly tame; the pair kept at home were taking food from my fingers within their first week, and all would readily walk over my hand without fear (although they objected strenuously to being held). They tended to remain out of their hide box for only about three hours after their heat lamp was turned on, after which they retired to their burrows, carefully closing off the opening, until the next day.
Initially, these lizards ate medium crickets (~1/2" [~1 cm] long), but after a few months of captivity began refusing crickets, preferring instead a diet of mealworms and waxworms. The individual that I caught in 1996 ate three 1" grasshoppers while I was chasing it! In captivity it eagerly accepted medium crickets.
- 14. Colorado Checkered Whiptail (Cnemidophorus tesselatus) complex
- This species is parthenogenic, the population consisting almost entirely of females, which are born fertile. There are actually two species in this complex that are native to Colorado. C. tesselatus is the result of hybridizing between two other species of whiptails: C. tigris, below, and C. gularis, a bisexual species not native to Colorado. C. tesselatus has one set of chromosomes from each parent species. C. neotesselatus is the result of an additional hybridizing, between a female C. tesselatus and a male C. sexlineatus, and has three sets of chromosomes, one from each parent species.
In 1996, I acquired a single specimen of this species (I believe it is a C. neotesselatus), captured by another member of the Colorado Herp. Society. So far its behavior is similar to the six-lined racerunners described above. The individual (the only one I have seen) is considerably larger and longer-lived than the six-lined variety. It has been thriving on ½" (1 cm) crickets so far. Whether an isolated female will produce fertile eggs remains to be seen. (Simulated mating behavior between females has been reported for the species; whether this is necessary for ovulation to occur is not yet known.)
- 15. Plateau Striped Whiptail (Cnemidophorus velox)
- I have not yet encountered this species anywhere. It is another parthenogenic species, found on the western slope of Colorado and elsewhere. From all I have read, its habits and behavior are the same as the other whiptail species described.
- 16. Western Whiptail (Cnemidophorus tigris)
- This is another species I have never captured in Colorado; I have caught them in California and Arizona. It is larger than the six-lined racerunner, and I have observed lizards of various sizes in the same population, indicating a longevity in the wild of three or more years. The last time I kept one in captivity was long enough ago that I do not remember their success rate, nor did I retain my old records. I do know of others, however, who have kept them in captivity with considerable success.
References:
Hammerson, Geoffrey A., 1986. Amphibians and Reptiles in Colorado, Colorado Division of Wildlife, Denver, Colorado, USA.
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