Gila Monsters and Beaded Lizards (escorpion)

Published in the English Version of the Spanish Herp Magazine "Reptilia" Volume 7 (June 1999)

The horrible suspicious venomous lizards of the new world. A rough translation from latin of the word Heloderma would be stud or decorative nail skin. Horridum would be frightful or horrible, and suspectum would be suspicious or distrusted. With scientific names like these, it is no wonder that the Gila Monster (Heloderma suspectum) and its southern cousin the Beaded Lizard (Heloderma horridum) have inspired superstitions, legends, fears and intrigue. It has been believed that their breath was poisoness, that a nursing mother would lose her milk if a Gila Monster crossed her path, and if stepped on sores would develope all over the unfortunate persons body. There are many stories, legends, etc., in American Indian folklore involving the Gila Monster.

The Gila Monster is found in the USA, southwestern states of Arizona, Utah, Nevada, New Mexico, and a small part of California. It ranges into Mexico south of Arizona down the Mexican West Coast until it meets and overlaps the range of the Beaded Lizard which continues south to Guatamala. There are no known intergrades where the two species overlap. Although locally scarce where human population has reduced their numbers, it is still common to see either in the more remote areas in their range. I have seen both crossing roads at night, but there is a seasonal varience in time of activity. Some recent research indicates Gila Monsters spend over 90% of their time underground.

Gila Monsters and Beaded lizards are common in captive collections. In the 1960's it was common practice to drive into Mexico, collect reptiles and amphibians for a week or so, then stop by any of several reptile dealers and buy as many Beaded lizards and Gila Monsters you wanted for about $20 US each. There were no laws at that time. You just declared your cargo at the USA-Mexican border, then took them home (I lived in the USA-California). Some of the Beaded lizards in my collection were purchased as young adults in 1970 and are still healthy and producing babies. They have a 30 year plus lifespan. Considering the large number of both Beaded lizards and Gila Monsters in captivity, there has been very little captive reproduction. In recent years these numbers are improving with the private interest in herpetoculture and the institutional emphasis on captive reproduction. There is now a North American Regional Beaded Lizard Studbook organized to list where various animals are held, and to coordinate breeding efforts. This group is also coordinating some mitochondrial DNA testing to determine which animals are from the same DNA groups. The results are not complete, but this will probably result in a revision of the subspecies of horridum.

Gila Monsters and Beaded lizards are protected in all parts of their range by law. There are legal captive bred specimens available from breeders, but permits are required to take any from the wild. Be careful who you buy from. I know of one example where several Gilas were wild collected and smuggled out of Arizona, and offered as captive hatched animals. One animal had been found on the road with a damaged eye, probably hit by a glancing blow by a passing auto. The smuggler did not charge the receiving dealer for that animal because the extent of the injury was not known and they thought the animal may die. The animal survived and later the dealer made up a story of how the animal had been stepped on while on his animal room floor, to explain the bad eye and was sold as captive hatched! There are other instances where authorities under cover will offer Gilas as wild caught, then later arrest the buyer for purchasing the animals. In one case the authorities broke the leg of the Gila so they could make a positive identification ofthat animal later when the new owner was arrested.

My personal involvement with Heloderma dates back over 30 years when I was dealing in reptiles commercially and Heloderma were one of the commodities I bought and sold. I made several trips into Mexico collecting and buying reptiles. When I heard my home state of California planned to prohibit the collecting and possession of Gila Monsters, I selected a few to use in my school lectures,notified authorities that I had them,obtained legal permission to keep them, and sold the rest before the law went into effect. In 1974 I had my first captive breeding and hatching of Gila Monsters , (I had hatched eggs from wild caught gravid females prior to that date). Then the battle with authorities to legally sell them began, but that is another entire article. Suffice to say I can now sell captive hatched Gilas and Beaded lizards. My current colony of Beaded lizards were acquired in 1987 from another who held them since 1970.

Heloderma are easy to maintain in captivity. My adults are kept in cages with a floor surface- measuring 3' by 3' with a height of 2 feet. Under each cage there are two drawers (1.5'x2.75'x5"h). There are 4" PVC pipes raised 2" above floor level that are glued into holes in the front floor area to allow the animals to go "underground" into either drawer. The 2" raised pipe keeps the upper substrate from falling into the drawer. I have water bowls large enough for the adults to soak and completely submerge without overflowing the container. Water is always available to the adults, but the cage is kept very dry. Please note that I live in a dry desert like environment, so keeping the cage dry is easy, but for those in a more humid environment you may have to remove the water for short periods to keep the background dry. There is a strip of heat tape, covered by metal 3" wide that provides a warm area in the rear of the cage. Heloderma are always digging and pushing things around the cage. It is important that any heavy cage furnishings be anchored, or the animals may dig under and have the furnishings (rocks, etc) squash the lizard. I have used many substrates in the past, (sand,carpet, newspaper) and because Heloderma are so powerful and very messy lizards, none has been completely satisfactory. You want the floor covered, but not so deep as to hide uneaten food or feces. The cage also needs to be kept dry. Recently I started using a chemical free mouse tray bedding of pellets of Aspen wood and it has worked better than anything else I have ever tried, (It works so great in my mouse room that I only have to clean once every 30 days!). It absorbs odors including amonia and has a nice "woodsy" smell. There is no direct cage lighting, just indirect sunlight coming into the room through normal double paned windows.

One of the more challenging aspects of establishing breeding groups of Heloderma is figuring out how to sex them. I have tried probing, examining the anal scale differences, and observing behavioral differences. The only animals I was sure of were the ones that laid eggs. There are subtle differences between head size and body configuration in adults. Males tend to have larger wider heads and narrower bodies than females. If you could observe a large group of adults, without captive fattened ones in the group you could pick out and identify most as male or female, but there would be a few you wouldn't be sure of. A few years back I tried the hypodermic injection of fluids into the tail to create pressure to evert the hemipenes of the males. I thought finally, here is the way to sex them! One of the females identified this way is now one of my breeder males, and I am hearing of some sort of gland or organ everting from females that is mistaken for a hemipene, so I am still in doubt. Dr Mark Seward of Colorado is pioneering a DNA sexing approach that has a lot of promise. For now, get as large a group as possible and wait for them to grow up.

Wild caught frequently and captive hatched occasionally will refuse to eat rodents regularly, or at all. Sometimes they will accept a young rat when they will refuse a mouse. One trick to entice them to feed on rodents is to dip the rodent in egg, then place it in a shallow dish. Use fertile eggs with more yellow or yolk if you can find them. Captive hatched babies will usually feed readily on new born mice, but occasionally a drop of egg yolk on the head of the pinkie, or the split brained technique is required (cut the brain encasement open and squeeze brain tissue out to the surface) for one to two feedings before they will accept normal mice. All my captive hatched Heloderma will take mice or rats from tongs. Even though there are many references to Heloderma consuming eggs in the wild, a nest of fertile partially developed eggs is not the same as infertile store bought chicken eggs. There has been a study that indicated rodent eating Heloderma will live longer than those maintained on eggs. The feces from rodent eaters is much easier to deal with also. Sometimes finding the right feeding combination is more difficult than just resorting to forcefeeding. Force feeding Heloderma is easy. So easy in fact that I force fed one female Gila from 1970 until 1989 because it was less trouble than messing with eggs then coming back later to clean the mess. Use smooth ended forceps, hold the mouse by the head, open the jaws and slide the rodent deep into the body and release. The force fed female laid eggs from 1974 thru 1989, so I doubt it bothered her much. I feed my Heloderma weekly when they are warm, unless the tails or the animals themselves become obese, when I reduce feedings to once every two weeks, and feed smaller amounts. My Beaded lizards can consume two 3/4 grown rats per meal, but I prefer to feed multiple smaller items. I I have had a Beaded lizard consume so large a meal just before laying eggs, that the meal could have forced the eggs out. I don't see how she could hold all those eggs and eat such a large meal.

In late October I stop feeding the Heloderma colonies. After a week or two with no food I shut the heat off and allow the cage to cool. I do have auxilliary heat that comes on at 60°F, but even at cooler temperatures the Heloderma usually avoid the heated area and retreat to the drawers underneath the floor of the cage. Occasionally an animal will lay on the warm area. I believe the Gilas can take a cooler winter "hibernation" temperature than the Beaded Lizards. I keep them cool until March 1. I believe this winter cooling is necessary for regular successful captive breeding of Heloderma. My colony has produced eggs regularly since 1974 except for a couple of years I kept them in my warm python and boa room. When they warm up I begin feeding and moving males from one group to another. This stimulates combat/breeding activity. I have observed copulation between long term cage mates, but the mixing and replacing of males allows me to observe copulations, which is when I collect a sperm sample and check it under a microscope at 200 power. Heloderma sperm looks more like a fat comma (Gila) with a tail, or a flat worm (Beaded), instead of like the slimmer snake sperm. Their movements are not as smooth either. This sperm check allows me to identify any non-sperm producing males, and if found, to back that mating up with another male. Neitman (1986) reports 10 copulations between April 18 and May 14 with eggs laid from May 31 thru June for Gila Monsters. Except for a clutch of 8 eggs laid July 3, my data supports his. My Beaded lizards copulate in May and June with eggs laid in July and August. My largest Beaded lizard egg clutch was 22 with 13 hatching. I have been lucky and found eggs in the community cage, but the laying female or cage mates will eat the eggs. It is difficult to be sure when a female is ready to lay eggs, but usually a puffiness around the rear legs can be observed. On one occasion I was giving a tour of my facilities to a visiting group of herpetologists, and as one viewed one of the Gila cages, he asked "do you let the female take care of her own eggs?". A very fast scramble to the cage and a safe removal of the eggs resulted. It is possible that the mothers are more likely to consume their own infertile eggs, but I don't know how to prove that theory. Gilas usually lay all their eggsin a few hours, Beaded lizards can take 24 hours to lay them all. I have had Beaded lizards lay good eggs over a period of several days. This was back in the early days and it might have been because of the lack of a suitable laying area, but others lay on the open floor of the drawers, so another unknown. If I believe a female is ready to lay eggs I will often remove her from her cage and put her in an aquarium 3/4 full of damp moss. Usually she will burrow to the bottom, lay her eggs, then come to the surface without eating them. You can check for eggs by tipping the aquarium and looking up through the glass bottom, avoiding disturbing the female by digging around her. I collect the eggs as they are laid, if I can safely do so without disturbing the female too much, but sometimes I have to wait until I feel she is through, and return her to her cage. Once I collect the eggs I place them inside a shallow open top plastic container with 1" of slightly dampened vermiculite or perolite. This tray is then "floated" inside another ventilated plastic box containing 1" of water, with a lid. These containers are then stacked inside my colubrid snake egg incubator which is set at 80°F. Gila Monsters hatch late Oct-Nov, the beaded lizards hatch the following Jan-Feb. I used to seperate the eggs into smaller containers, 2-4 eggs per container, when hatching time was near, and the lizards would hatch over a week or more of time. Recently I left a large group together and they all hatched within a couple of days. Perhaps the movement of the early hatched lizards stimulated the others to come out. This is another observation without enough data to support the hypothesis. Gilas usually weigh 27-39 grams, Beaded lizards 36-50 grams at hatching. The baby lizards are individually housed in plastic boxes in a typical rack system designed for baby snakes, heat in the rear of the cage. I use newspaper as a subtrate, and provide a water bowl not large enough to soak in. The lizards usually make a wet mess out of their cage, so water bowl is removed and the cage is allowed to dry. It is important the lizards not be kept too dry too long as babies dessicate easily.

Cleaning the cage is easy. A mouse is offered on tongs. The lizard attaches itself to the mouse. Both are lifted and placed in a bucket. I clean the cage, the the lizard eats the mouse, then I dump the lizard back into the clean cage. As soon as you place the lizard into a clean cage, expect it to deficate soon. It doesn't seem to matter how long ago it fed. Perhaps they are marking their territories? Warning: As wonderful as these lizards are, they are dangerous. Their venom is very potent. A bite at a local zoo resulted in an inconscious, near death person in less than 30 minutes. There are recorded deaths from bites, extreme pain in others. Procede with caution.

I have had the privilege to care for these remarkable animals for over 30 years, and I still can't answer all the questions about them. In fact I am sure we don't even know all the questions yet. If we look back at the advances in herpetoculture in the last 20 years,it is nothing less than fantastic, but I hope 20 years from now I can look back on our advances. I have a feeling we are now at a primitive stage of development. Best wishes for Heloderma happiness.


I would like to acknowledge herpetoculturists in general and the spirit of sharing knowledge with others, Dr. Mark Seward, for sharing general information and info on his DNA sexing, and specifically my lovely wife Marilee who not only adapted well to a life with reptiles, but who now takes care of 100's of baby snakes and the baby Heloderma. They call her Mom.

Beck, Dan 1990 Ecology and Behavior of the Gila Monster in SW Utah. In Journal of Herpetology Vol 24, No 1. pp 54-68 SSAR Publication

Gotch, A.F.1986 Reptiles- Their Latin Names Explained

Blanford Press Dorset England

Neitman, K 1986 Captive Reproduction ofthe Gila Monster "Heloderma suspectum" at the Houston Zoo In: Peterson, C.H.(Ed) Proceedings of the 10th International Herpetological Symposium PP 119-123 Private Printing

Perry, Janice (Craig Ivanyi) 1998 North American Regional Beaded Lizard Studbook, 2nd Edition Pub Arizona-Sonora Desert Museum Tucson, Arizona USA

Robert W Applegate POB 338 Campo, CA 91906 USA Phone (619) 478-5123 E Mail: ApplesnakeŽ