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Day 153: It happens! Gila monster hatching success!

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So, almost after all hope was lost on Day 153 the first Gila monster egg pipped from its leathery shell! Egg 02 at first cut a small slit and then a few more and over the next two days began to emerge from the egg. At first the baby Gila stuck its nose out, then it’s head, then half its body, and finally the entire body. It appears that hatching is a labor-intensive process as there are long pauses between progressive stages and also seems to be a good way of ensuring all the contents of the egg are consumed before leaving the egg. Over the ensuing days this process was (and currently is for two more lizards) repeated over and over, with Gilas emerging from their shell about two or so full days from pip to full emergence. Once the contents are completely devoured the neonate Gila monster leaves its shell and begins to wander the egg box. I witnessed one Gila that was out actually eating the egg yolk of another just coming out of its shell! Greedy bastard.

Once fully emerged and climbing around, the little monsters are pulled from the egg box, photographed, weighed, and set up solo in an 18 quart Sterelite box with paper towels as bedding and small water dish. The paper towel bedding serves as a clean substrate while the umbilical wound heals and the first few meals are eaten and passed through to make sure everything is going well. I will attempt the first feeding next week after the yolk has been fully digested and look forward to raising the babies from there!

I will be posting updates on the neonates growth, as well as some thoughts and insights on my first season captive breeding Gila monsters. Some reviews of the equipment I used is also likely in order as these items played an important role in my success. Whew, what an amazing season! The process has been fun, though frustrating and worrisome at times, and I look forward to greater success next year with these amazing reptiles!

Day 152: A watched egg never hatches

A Gila monster near hatch datePatience. Patience is what those in the know say. Sure, I am checking the incubator at least ten times a day for any action and patience is not my virtue, but I am old enough to know when to listen. A couple a the eggs dented in over two weeks ago, the two others are starting to dimple (not dent) and in all honesty I would be surprised if any of them hatch at this point. If they do not hatch my biggest concern is figuring out where my failure was. Is it the incubator? No, the Grumbach’s are renowned for their reliability. Is it the S.I.M. egg container? No, these have been used successfully with Gila monsters before. My temperature, though low, should not be the issue and my humidity is spot on, so it shouldn’t be that. We just started having cold fronts move through and temps have fallen so that may have a slight play into it (I have ordered a space heater to remedy this issue). At this point my guess is that since the fan in the Grumbach is unplugged that there may not be enough airflow which may be an issue, or the fact that the Pangea Hatch medium has started to grow mold adds to this theory. I do open the incubator to allow fresh air to enter but it may not be enough. Whatever the case, I will hold on hope until the last egg turns yellow and starts to sweat. If they all die I will carefully review my protocols and notes and seek the advise of successful breeders to plan for a better year next season!

On another note, I have stopped feeding my adults and am turning off the lights and under-cage heating in preparation of hibernation, which will begin after Thanksgiving. I have an old refrigerator that is hooked up to a Ranco thermostat for the cool down. Would be great if I could cool them in their cages but we do not see steady enough low temps here in northern Florida to ensure the Gila will reach and stay at 53°F for the three months of brumation.

Gila monster egg death. Goodnight sweet prince..

About a week or so ago, I noticed that Egg 10 was not looking so good. As only six eggs remained viable it is a hard hit when one is lost. I had kept it in the egg box in hopes it would turn around but after waiting a few days the egg started to sweat and smell so I candled it to see what was happening inside. No veins were present and there was a lot of clear yellow mass which was present in all the other eggs that died, so I knew it was no longer viable. Still hoping, I left it in the egg box for a few more days but it continued to deteriorate and smell so tonight it was removed.

After removing the egg I was morbidly curious to see what was going on, and how far the embryo had developed. Sadly, a fully-formed Gila monster was inside. It was much smaller than the typical hatchling but appeared normal overall. Why did this embryo die after being alive for so long? Has it been dead for a long time? It’s hard for me to say at this point with my limited knowledge, but I really hope that the other five eggs are healthy and hatch. Regardless of how this season turns out I am going to thoroughly review my notes and protocols and see where improvements can be made and where things may have gone wrong. At this point, my feeling is that the females were not prepared last year for this season. Maybe it was improper temperatures or not enough food but this year I know all my adults are in proper order and ready for next year. I’m not giving up on this season yet and still have hope that the five remaining eggs will sprout baby monsters in the next few weeks!

Harmony Kingdom goes Gila monster in Tip the Scales

I started collecting Harmony Kingdom boxes in the mid-90’s after discovering them at a collectibles shop in the mall. They were mostly animal and my first box was, of course, a reptile (chameleons). For those that don’t know, Harmony Kingdom is a collectible series of themed boxes and figurines crafted by artisans in the United Kingdom. What caught my eye was the attention to detail and thoughtfulness put into the designs, with a nice dose of cheeky British humor. Though my collecting has slowed down over the years, I was very into it for some time and in an almost obligatory move mailed the company requesting a Gila monster box. Not saying that my letter reached the highest echelons of Harmony Kingdom or that it was even read, but in late 2009 the company released two versions of our favorite venomous lizard (you’re welcome).

Tip the Scales was carved by Master Carver Peter Calvesbert, hand-painted by local artisans in the Cotswold region of England, and comes in two versions. V1 is a normal colored Gila monster limited to 300 pieces, while Tip the Scales V2 is more of a bone-colored Gila and limited to 100 pieces worldwide! Very low numbers for the typical run for Treasure Jests and quite collectible.

These boxes are a must-have for any Gila monster enthusiast. The detail on these boxes is amazing, especially considering their diminutive size. The osteoderms look real as do the proportions of the body and look of the lizard. Besides the great detail and the beauty of these boxes, there are a some cool Easter eggs for us enthusiasts. Here is what the card that comes with the boxes say: “The Gila monster is a venomous lizard native to the southwestern U.S. and northern Mexico. Not only did Peter painstakingly sculpt its reticulated pattern, but he included numerous secrets. Its Latin name, Heloderma suspectum, means studded skin. Suspectum derives from palaeontologist Edward Drinker Cope’s suspicion that the lizard may be poisonous due to its teeth grooves. Gila refers to the Gila River Basin in Arizona, where these lizards were once plentiful. Exenatide is a drug used in the treatment of diabetes and is a synthetic version of a hormone found in the saliva of the Gila monster. Open the lid of this fixed edition box figurine to find a baby hatching Gila and Peter’s initials under one of the rocks.” The tent cards (cards that come inside the boxes and to be set up for retail display) can be downloaded from the Harmony Kingdom website here: V1  V2

The boxes pop up on eBay from time to time, and I have even seen one languishing in a store that needed rescue! So, have some fun and look for one or both of these amazing Harmony Kingdom Gila monster boxes, you will not be disappointed!!

New Gila Monster book from Dr. Hans-Joachim Schwandt

Fans of the fantastic website Heloderma.net already know how knowledgeable and passionate Dr. Schwandt is about Gila monsters, and in September 2019 he released his long-awaited book on our favorite subject. Being the Gila geek I am, my order was placed the day pre-orders were announced and was certainly not disappointed when it arrived. The book covers a wide range of topics in detail and covers some information not previously seen in other books. Certainly a must-have for your collection of Heloderma reading, the book can be purchased from the author on his website or here.

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.

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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. 
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The sweating of the egg on the left is a sure sign of bad things to come.
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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!!