Heloderma Bibliography

A few Heloderma books from my collection.

The Yahoo! Heloderma group created and maintained by Mark Miller is being taken down. So, I thought it would be a shame to let Mark’s work fade into oblivion and have posted his well-curated Heloderma Bibliography here for posterity. One of these days I will update this list with some of the newer books that have come out since it was compiled.

CREATED by Mark Miller / UPDATED circa 1998 by Mark Miller

Allen, Morrow J. 1933. Report on a collection of Amphibians and reptiles from Sonora, Mexico, with the description of a  new lizard. Occas. Papers Mus. Zool. Univ. Michigan, no. 259, pp.1-15

Arnberger, L. P. 1948. Gila monster swallows quail eggs whole. Herpetologica, vol. 4, pp. 209-210

Beddard, Frank E. 1906. On the vascular system of Heloderma, with notes on that of the monitors and crocodiles. Proc. Zool. Soc. London 1906:601-625, 8 fig.

Bloyd, Gary R. 1970. The gila monster (Heloderma suspectum). Bull. Florissant Herpetol. Soc. (8):1-2.

Bogert, Charles M., and Rafael Martin del Campo. 1952. Geoclines and ontoclines in lizards of the genus Heloderma. Annu. Meet. Amer. Soc. Ichthyol. Herpetol. 32nd., Austin, Texas.

Bogert, Charles M., and Rafael Martin del Campo. 1956. The Gila Monster and its allies: the relationships, habits, and behavior of the lizards of the Family Helodermatidae. Bull. Amer. Mus. Natur. Hist. 109:1-238, 35 fig., 20 pl., 5 tab., 2 Maps.

Boulenger, Georges Albert. 1891. The anatomy of Heloderma. Nature (London) 44:444.

Boulenger, Georges Albert. 1891. Notes on the osteology of Heloderma horridum and H. suspectum, with remarks on the systematics position of the Helodermatidae and on the Vertebrae of the Lacertilia. Proc. Zool. Soc. London 1891:109-118.

Boulenger, Georges Albert. 1918. Les lezards Helodermatides de l’Eocene Superieur de la France. Comp. Rend. Acad. Sci. (Paris) D 166:889-893.

Cheek, L.W. Watch Out! The Little Monsters Bite. Arizona Highways 1990 Vol. 88 (8): 42-46

Cooper, Robert H. 1969. Melanoma in Heloderma suspectum Cope. Proc. Indiana Acad. Sci. 78:466-467.

Cuesta Terron, Carlos. 1934. El escorpion. Heloderma horridum  Wiegmann. 2a Ed. revisada por Rafel Martin del Campo. pp. 1-14. Folletos Divulgacion Client., Inst. Biol., Univ. Nac. Mexico.

Curtis, L. 1949. Notes on the eggs of Heloderma horridum. Herpetologica 5(6):148.

Dolensek, E.P., Cook, R.A. Clinical Challenge [Radiographs of enteritis due to Salmonella infection in a Gila monster (Heloderma s. suspectum)]. J Zoo Animal Medicine 1987. 18 (4): 168-170

Durham, Floyd E. 1951. Observations on a captive Gila Monster. Amer. Midland Nat., vol. 45, pp. 460-470, 1 table.

Edwards, H. T., and D. B. Dill. 1935. Properties of reptilian blood. II. The gila monster (Heloderma suspectum Cope). J. Cell Comp. Physiol. 6(1):21-35, 5 fig., 5 tab.

Funk, Richard S. 1966. Notes about Heloderma suspectum along the western extremity of its range. Herpetologica 22(4):254-258.

Grasse, Pierre-P. 1970. Les glandes venimeuses et le venin des sauriens helodermatides, p. 676-680, fig. 454, In, Pierre-P. Grasse, Traite de zoologie, anatomie, systematique, biologie, vol. 14. Reptiles, Fasc 2, Caracteres generaux et anatomie. Masson et Cie Ed., Paris.

Haddon, E.P. 1954. Little monster. Outdoor Life, vol. 114, pp. 46-49, 15 illus.

Hensley, M. Max 1949. Mammal diet of Heloderma. Herpetologica, vol. 5, p.152

Kauffeld, Carl F. 1943. Field notes on some Arizona reptiles and amphibians. Amer. Midland Nat., vol. 29, pp.342-359, 4 illus.

King, F. Willis 1932. Herpetological records and notes from the vicinity of Tucson, Arizona, July/August 1930. Copeia, pp.175-177.

Komori, K; Nikai, T; Sugihara, H. Purification and characterization of a lethal toxin from the venom of Heloderma horridum horridum.  1988. Biochem. and Biophysical Research Communications. Vol 154 (2): 613-619

Koster, William J. 1951. The distribution of the Gila monster in  New Mexico. Herpetologica, vol. 7, pp.97-101, map.

Matthey, Robert. 1931. Chromosomes de sauriens: Helodermatidae, Varanidae, Xantusiisae, Anniellidae, Anguidae. Bull. Soc. Vaudoise Sci. Natur. 57:269.

Mebs, Dietrich. 1968. Some studies on the biochemistry of the venom gland of Heloderma horridum. Toxicon 5(3):225-226, 1 fig.

Mebs, Dietrich. 1969. Isolation and properties of kallikrein from the venom of the gila monster (Heloderma suspectum). Hoppe-Seyler’s Z. Physiol. Chem. 350:821-826, 3 fig., 2 tab. (Germ., Engl. summ.).

Mebs, Dietrich. 1969. Purification and properties of a kinin liberating enzyme from the venom of Heloderma suspectum. Naunyn-Schmiedebergs Arch. Pharmakol. Exp. Pathol. 264(3):280. (Germ.).

Mebs, Dietrich. 1970. Biochemistry of Heloderma venom. Int. Symp. Anim. Plant Toxins 2nd Progr.:64-65. (abstr.).

Mebs, Dietrich. 1970. Biochemistry of Heloderma venom. Toxicon 8(2):142-143 (abstr.).

Mebs, Dietrich. 1970. Biochemistry of kinin-releasing enzymes in the venom of the viper Bitis gabonica and of the lizard Heloderma suspectum, pp. 107-116, 6 fig., 2 tab., In, F. Sicuteri, M. Rocha e Silva and Nathan Back (Eds.), Bradykinin and related kinins: cardiovascular, biochemical and neural actions. Plenum Press, New York.

Mebs, Dietrich. 1970. Untersuchungen ueber die wirksamkeit einiger schlangengift-seren gegenueber Heloderma-gift. Salamandra 6(3-4):135-136 (Engl. summ.).

Mebs, Dietrich, and H. W. Raudonat. 1967. Biochemie des giftes der krustenechsen Heloderma suspectum und Heloderma horridum. Naturwissenschaften 54(18):494.

Mebs, Dietrich, and H. W. Raudonat. 1968. Biochemical investigations on Heloderma venom. Mem. Inst. Butantan 33(3):907-911, 4 fig.

Michl, H. 1972. (Review of) Untersuchungen ueber die wirksamkeit einiger schlangengift-seren gegenueber Heloderma-gift, by Dietrich Mebs, 1970. Toxicon 10(2):189.

Mulch, Ernie 1952. Why protect Gila monsters? Arizona Wildlife- Sportsman, vol. 23, no. 9, pp. 30-31, 71, 1pl.

Patterson, Robert A., and In Soon Lee. 1969. Effects of Heloderma suspectum venom on blood coagulation. Toxicon 7(4):321-324, 4 tab.

Pregill, G.K.;Gauthier, J.A.;Greene, H.W. 1986 The Evolution of Helodermatid Squamates with Description of a New Taxon and an Overview of Varanoidea (Trans. San Diego Soc. Nat. Hist 21 (11): 167-292

Shaw, Charles E. 1968. Reproduction of the gila monster (Heloderma suspectum) at the San Diego Zoo. Zool. Garten 35(1-2):1-6, 3 fig.

Shufeldt, R. W. 1890. Contributions to the study of Heloderma suspectum. Proc. Zool. Soc. London 1890:148-244, 3 pl.

Stahnke, Herbert L. 1950. the food of the Gila monster.  Herpetologica, vol.6, pp.103-106.

Strel’nikov, L.D. 1944. Snachenie solnechnoi radiatsii v  ekologii vysokgornyh reptilii. [Importance of solar radiation in the ecology of high mountain reptiles.] Zool Zhur., Moscow, vol. 23, pp. 250-257.

Taub, Aaron M. 1963. On the longevity and fecundity of Heloderma horridum horridum. Herpetologica 19:149.

Trutnau, Ludwig. 1968. Gefangenschafts-beobachtungen an krustenechsen (Heloderma suspectum Cope). Aquarien Terrarien Z. 21(4):120-125, 10 fig.

Trutnau, Ludwig. 1970. Ein beitrag zur behandlung erkrankter krustenechsen (Heloderma horridum und Heloderma suspectum). Aquarien Terrarien Z. 23(8):251-253, photos.

Trutnau, Ludwig. 1970. Die skorpion-krustenechse Heloderma horridum (Wiegmann). Aquarien Terrarien Z. 17(7):228-231, 5 fig.

Tu, Anthony T., and David S. Murdock. 1967. Protein nature and some enzymatic properties of the lizard Heloderma suspectum suspectum (Gila monster) venom. Comp. Biochem. Physiol. 22(2):389-396, 6 fig., 1 tab.

Tu, Anthony T., and David S. Murdock. 1967. Protein nature of Gila monster (Heloderma suspectum suspectum) venom. Int. Congr. Biochem. 7th., Tokyo (abstr.).

Van Denburgh, John. 1922. Helodermatidae in Reptiles of Western North America… Vol. 1: 470-476, plt 44-47. SF Acad. Sciences

Vandermeeers, Andre; et al. Chemical, immunological and biological properties of peptides like vasoactive-intestional-peptide and peptide-histidine-isoleucinamide extracted from the venom of two  lizards (Heloderma horridum and Heloderma suspectum) Eur. J. Biochem. 164, 321-327 (1987).

Vorhies, Charles T. 1917. Heloderma suspectum, automobile tourists and animal distribution. Science, vol. 68, pp. 182-183

Wagner, Ernie; Smith, R.;Slavens, F. 1976. Breeding the Gila monster in captivity. International Zoo Yearbook, Vol. 16

Willey, D.A. 1906 Gila monsters. Sci. American, vol. 95, p. 192

Day 132: So close, but so far!

R0000020We are 132 days past oviposition and the remaining six eggs appear to be hanging in there. One of the eggs has dented in, which I am hoping means that it will hatch in the next few weeks and does not mean the embryo has died. The other eggs remain rigid and appear to be well, fingers crossed they come to term! The Grumbach has been great in maintaining the temperature and humidity stable throughout incubation, but I have noticed that the egg boxes have increased in temperature by 1°F higher than the incubator over the last few weeks. Condensation has also started to build up (mostly on the sides) so I’ve been keeping an eye on that to ensure none falls on the eggs potentially suffocating the embryo inside. Since the eggs were incubated at the lower end of the range it can be expected that the eggs will hatch (if they do) toward the later end of the spectrum, potentially 150+ days. Man, I can’t wait…

On the other side of the house my adult Gilas are getting ready for next year. Weekly feedings of 2-3 mice (2 for the males, 3 for the females) has brought all of the Gilas to a healthy state; good fat reserves in the tails and a constant, though not concerning, weight gain. As most of my group was purchased earlier in 2019 and after the hibernation cycle, I do not have data on what the pre-hibernation weights were last year but I think they are ahead as their weights are above pre-breeding numbers from this season. I hope to have more fertile eggs that make it to term in the upcoming season as they entire group will have been with me for the whole cycle.

Winter cooling is going to start in late November and this year a larger refrigerator / cooler is going to be purchased in order to facilitate all adults. I’ve noticed an increase in activity and feeding response in the adults over the past week, almost being as active as breeding season. I do not know if this has to do with growing follicles and testes, a reduced photoperiod, or slight drop in temperature (or maybe all) but it does seem that the Gilas are getting ready for a long winter’s nap!

That’s all for now, hopefully the next post is of the Gilas hatching!!

Day 102: How long do Gila monster eggs incubate?

Mark Seward says 124 – 150 days. I am at Day 102 and it’s hard to be patient. Six eggs remain in the incubator and I have not touched them in some time for fear of creating a problem that didn’t exist. The Grumbach has done an admirable job of keeping both temperature and humidity very stable, and the S.I.M. Containers are keeping the eggs off the moist substrate while maintaining 100% relative humidity so as long as the eggs are good there’s a fair chance in the next 48 days baby monsters will grace my home! As the time nears I need to watch out for excessive condensation in the egg containers, though there is none now, as this can cause egg death.

In other news, all the Gilas in my breeding group are at a good weight and ready for the winter cooling. An interesting observation that I have made over the past few months is that it has taken a lot longer for the females to get back up to weight despite being fed more (three mice per week instead of two). The females have also remained generally more active than the males, which probably attributes to their slower weight gain. I hope to get another female before winter cooling, but am looking for the right Gila to add to the group. This year I plan on modifying an old refrigerator to hibernate the Gilas in as I do not think it gets cool enough for long enough to reach and sustain the appropriate temperatures. Will post pics here of this year’s set up so stay tuned. But, hopefully a few Gila babies first…

Update 5: Waiting is the hardest part

L1195359Not much has happened since the last update; one good egg died leaving me eight healthy growing eggs in the Grumbach incubator. A universal agreement on Gila monster eggs is to leave them the F* alone during the long incubation time. I have a hard time doing this but have been a good bean and done so by only check through the incubator’s clear door and light to make sure none are dying. The Grumbach is holding temps and humidity as it should; Temperature ranges from 77.5˚F to 79.5˚F and humidity in the incubator stays at a steady ±90% RH (relative humidity) with the Squamata Concepts S.I.M. egg boxes at 100% RH. I have three SensorPush sensors (one in each egg box, one in the incubator) connected to a SensorPush Gateway to monitor temperature and humidity. And the Gilas? All are eating and back to normal, with the females gaining weight nicely. I still find it interesting how the feeding habits changed so much during the breeding season and look forward to more data next year from this interring period of time.

The egg on the right was good with a solid blood ring and growing nicely with nice veins before it suddenly died. Not sure what happened as the others in the clutch continue to grow. 
The sweating of the egg on the left is a sure sign of bad things to come.
These eggs look good and smell like fresh, moist soil. The SensorPush sensor is placed in each egg box to track temperature and humidity.

I wanted to post a few photos of good eggs and bad / dead eggs (see above) and discuss a few observations. When an egg goes bad, there is no mistaking it; they begin to sweat, discolor, and smell awfully. The good eggs remain turgid and whitish in color, with increasing veining (last I checked a few weeks ago) when candled. I do not plan to open the incubator door again unless something is going wrong or an egg dies, so hopefully they are growing and not just looking good….

My next post will be one on the tools being used in my program for Gila monster breeding and incubation.

Thanks for stopping by!!

Update 4: Eggstravaganza!!

Gila 03 “Belle” dropping her second egg.

It’s been all quite on the update front as, well, there has not been much to report. Until now, that is! On Friday June 7, Gila 03 dropped one egg over the night and I came upon it at 6am when getting up for work. I candled the egg but did not see a blood ring (something that viable eggs have) but put the egg into an egg box just in case. For those that have not heard of this stuff yet, candling is using a flashlight to light up the egg to see what is going on inside. The blood ring is the blastoderm that will one day become a baby. No blood ring, no baby. Gila 03 did not drop her eggs in succession and the next one came Friday night around 10pm. This egg also did not look viable, but was more solid than the first. The third egg from 03 came Saturday afternoon and had a clear, but small (dime-sized) blood ring. I think 03 has more eggs in her, but she hasn’t dropped yet. Now when will little 05 drop her eggs….


Candling a freshly-laid Gila monster egg. The blood ring is readily visible upon inspection.

That answer came Sunday morning when I got up around 7am and two eggs were in the nest box. Two, beautiful healthy eggs! Now, 05 is on the smaller side (757 grams pre-breeding season) so I did not expect many eggs from her but over the course of the next eight hours she would go on to lay a total of six viable eggs! Poor girl, she looks exhausted.

Gila 05 “Heather” dropped her first two eggs over the night.
Heather on egg #4! Look at the size of that thing!!

Now is the hardest part, incubation. I hope everything is set up right in the Grumbach S84 as I’ve had the humidity (90%RH) and temperature (79°F) dialed in for a month now. I opted to go for a lower temperature as outside temps have hit over 100°F in May so I expect the Summer to be pretty hot and I do not want the eggs exposed to high temperatures.

I’ll post some more thoughts and data that have been collected in the meanwhile, but fingers crossed the eggs make it to term and we have baby monsters in the Fall!

Update 3: Sitting, watching, waiting.

So, I made a third update some weeks ago but found out I never posted it, so here it goes…

UPDATE 3 – May 3, 2019

The females had been separated from the males for about two weeks now as I observed both females being copulated with and, according to other successful breeders, mating is wrapped in in a two week period. Though both weight and girth were increasing on both females, I felt extremely paranoid that breeding was not over and pulled them out prematurely (no pun intended). After searching through Internet forums and FB posts, it did appear that I may have separated the sexes too early. A few successful breeders commented on some of my posts how they usually separate mid-May, or when the female appears to be gravid.

Gravid or ovulating? This is the beginning of May.

So, I figure better safe than sorry and put the pairs back together. What also came out of this was the insight that Gilas become pairs, meaning that success can be enhanced by putting two “known” pairs together and that they will successfully breed together in the future without male combat or by cycling through male cages. I cannot comment on this but it does seem that certain Gilas do pair together and prefer one another. In my example, Gila 01 and 05 successfully mated and remained close together whenever introduced to each other. Conversely, Gila 01 and 03 were not close to each other though they did successfully mate. The same with Gila 04 and 05, though 04 did not mate with 05 and they were always on opposite sides of the terrarium. Gilas 06 and 09, both males, stay home without dates this year. Gila 06 remains quarantined while 09 was not preferred by either females despite his most earnest effort.

03 and 04 get reaquainted

After re-introducing Gila 03 and 04, Male 04 wasted no time in getting to it. Unlike earlier in the season where the males chased the females and copulation took place later, this interaction was direct and immediate. Though I suspect that 03 was already gravid I think it was good for him to actually copulate this season; he began eating again after he sowed his wild oats. His activity level also calmed a bit after having his girlfriend back in his territory. I observed copulation with this pair four more times while 01 and 05 did not hook up again though they remained close together.

I will separate the pairs on May 11 as I am pretty sure the females are gravid, but want to be sure. It is fascinating to me how the Gilas know one from another and have different choices in mates. In the wild it is reported that Gilas visit the same dens to breed year after year. Not sure of the same lizard if there each time, but think it means they are familiar with the area and hope to find an old flame that they previously has a successful connection with.

The Grumbach S84 Incubator for Reptile Egg Incubation

Grumbach S84 Compact Incubator

I discovered Grumbach incubators from the book Beaded Lizards & Gila Monsters Captive Care & Husbandry which states that “Grumbach incubators are especially well suited for hatching Heloderma eggs”. After some Google searching and browsing through reptile forums I quickly found that the problem with Grumbach, a German manufacturer, is that these machines are not commonly used in the US (especially for reptile egg incubation) and finding information about their incubators and how they are used is scant. The sole distributor here in the States, Lyon USA, seems to have disappeared. The Grumbach website does have English instructions for their incubators so, armed with what little knowledge was available it was off to eBay. As luck would have it I found an older analog Grumbach S84 Compact model for a fair price and picked it up. After downloading the manual from the Grumbach website I sent the next few weeks attempting to get the incubator to where I needed it to be; 82*F with a 90% humidity. But no matter what I tried the coolest stable temperature I could get down to was 89*F. Way too hot for Gila monster eggs! The S84 was made for hatching birds, so I contacted Grumbach directly to see if this unit could be used for reptiles (they have several reptile specific incubators, but again getting one here in the US is a very expensive proposition). They did get back to me and said that the S84 could be used for this, but they did not give me guidance on how to get the temperature to where I needed it. Frustrated, I sold the Grumbach since it was apparent the incubator would not work for my purposes and I did not want to modify or damage this fully functional unit. The hunt for another incubator began.

Then, again on eBay, another S84 popped up but this one was being sold for parts and not working for a deep discount. I figured this unit would be a better fit as I could modify it to fit my needs without having to worry about losing too much money if it didn’t work out. The owner reported that they only tested the incubator on 110v (the Grumbach’s are 220v) so they weren’t sure what worked and what didn’t. This model was digital so, to me, it was worth the risk. The unit arrived and once properly hooked up to my Todd Systems 115v to 220v step-up transformer I was able to get most of the components up and running properly. The exception being the fan. The Heidolph fan was dead and upon contacting Lyon USA found out that Grumbach no longer supplies a replacement and the entire unit (fan, heater, assembly) had to be purchased at a cost of $800! It appears that Heidolph produced these fans specially for Grumbach as I couldn’t find a replacement anywhere. Buying a new unit obviously wipes out any cost savings of purchasing this unit so I started researching other options and found an Ebmpapst 4850 ZW 220v fan, which some Grumbach’s use, to fill the position and it works well! This unit pushes a lower cfm (cubic feet per minute) than most of the others I looked at which is an important factor as we do not need a hurricane to dry the eggs out or draw out the moisture, only for moving the air to provide a consistent temperature.

I want to take a moment to mention again that Grumbach incubators are 220v. Here in the US, our outlets are 110v and a step-up transformer is necessary to properly operate the unit. When I started researching transformers, it quickly became apparent that this was an area to not skimp on. The abundance of lower cost and quality units which are readily available on Amazon and eBay make it seem like they are all the same, but that is far from the case. Perhaps for intermittent use these cheap units would be fine but my incubator will be running continuously for 5-6 months! I read horror stories of how these cheaper units run hot and can catch on fire after a few hours of use, and that you need to double their wattage (if your unit uses 500w, you need a minimum of 1000w or greater transformer) to ensure proper power is supplied. After all these years and planning, the last thing I want is for a cheap component to ruin my eggs, or even worse burn my house down! So, more research ensued and I found a few high-quality transformers; the one I bought from Todd Systems and there was another company ACUPWR, that made equally good equipment.

Step-up transformer 120v – 220v
Old Heidolph fan that has died.

I set up the incubator well in advance of oviposition to make sure the eggs go straight into a stable environment. I don’t know why, but this second Grumbach was able to achieve the conditions required for incubating Gila monster eggs and it didn’t take long to get everything dialed in. I placed a SensorPush digital thermometer / hygrometer to track my temperature and humidity, as well as some Squamata Concepts S.I.M. egg containers in the incubator and think I am all set. All I need now is the eggs!

All set and ready for some eggs!

I cannot yet comment on how good the Grumbach S84 incubator will be for Gila monster eggs, but feel it should be adequate as it is well insulated and maintains a very steady temperature and humidity while the fan provides a consistent temperature throughout the unit. I must say that it is cool how the digital display can be seen in the dark across the room for obsessive checking:) I’m sure other incubators and DIY units can do the same job, but Grumbach is world renowned and I am fascinated by German engineering (thanks, Leica!). I’ll revise this post after the first year and report how well it does and if I’ll be sticking with it for upcoming hatches.

Update: June 12, 2020

Now that the first successful year of breeding Gila monsters is behind me and the second season is well under way, I wanted to update this post with some additional thoughts on the Grumbach S84 incubator.

The first year, I did not find a good solution for circulating the air and ended up not having a fan at all. Only 5 of 13 eggs hatched (though 4 were bad out of the gate) and I wondered if there may have been a lack of fresh oxygen to sufficiently allow the eggs to grow. This was an area I wanted to improve in 2020 and have found a good solution. I found that 220v fans increased the temperature in the incubator by 8* – 10*F which put the temperature too high for my comfort. Last year, the incubator averaged 78.2*F without the fan, which would put the temps in the mid 80’s and on a hot summer day could wind up in the upper 80’s – certain disaster! Keeping in mind heat from the tank that maintains the humidity also adds a temperature increase, I started off with a 12v computer fan plugged into a 120v converter. Temperature only increased a degree or two, so things were looking promising. I wanted to try a native 120v fan with low wattage and RPM’s to keep the temp low, and found the AC Infinity 8038 axial muffin fan on Amazon which can be purchased with a separate speed controller. My interest was piqued as this fan, of all the AC Infinity 120v fans, only used 4 watts of power and moved 23 cubic feet per minute so it fit the parameters that should work for this application. With a quick order and Prime delivery the fan and controller were at my house in short order and installed for testing. After a few weeks of adjustment between fan speed and humidity control I was able to dial in a steady temperature of 81*F and 90% relative humidity, perfect! Temperature and humidity were constantly monitored (and checked) with my SensorPush system; one sensor in the incubator and one in the egg box. Time will tell if the fan holds up to the high humidity, but the fan seems very well made and I love the external speed controller. With eggs in the incubator now, I am hopeful this new set up will help increase my success in 2020!

I still love this incubator and agree it is an excellent choice for incubating Heloderma eggs. Parts are scarce and expensive, but things are working good for now. One of these days I need to pick up another Grumbach S84 just in case this one fails or I get more pairs of Gila monsters to breed!

Just when you think you know someone…


Gila monster 06, formerly known as Joy, was thought to be a female and was the one that was sick. Now that Joy is better, I wanted to finally determine confirm her sex (though based on head size I guessed female). My intention was not to breed, only to watch the reaction and once I put Joy in the cage with a known male (one from the group she came from) Joy went right into battle mode and started wrestling with the other male. There went that theory. The girl formerly known as Joy is now a boy named Floyd. No more gender dysphoria. You be you, Floyd.

Battle Royale: Thunder vs. Floyd

Why do Gila monsters play dead?

My first encounter with this behavior was many years ago when my best friend saw the Gila monster in its cage upside down and unmoving. He called in a panic and said that my pink lizard (his reference of Gila monsters to this day) was dead. Of course when the cage was opened the lizard sprang to life and was quite aggressive upon examination. Now that I have a group of Gilas, I see this behavior often. Above are a few examples of what this looks like.

I wonder why Gila monsters do this. Is it to thermoregulate different parts of the body? Does it aid in digestion? Maybe its like having restless leg syndrome and they just can’t get comfortable! This behavior is bizarre, but I must say that Gila monsters are quite interesting and they do some funny things I have not seen other reptiles do. I think a book on captive behavior alone would be a fun read!