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!

Joy’s pain: a Gila monster’s road to recovery


When I purchased the six Gila monsters, No. 6 (now known as Joy) was the only one that looked a little off; she was skinnier than the rest and her fat reserves in her tail were depleted. I thought it may have been from overwintering but that was not to be the case as it quickly became apparent she was sick. She excreted a red mass of bloody stool, was listless, did not eat and was losing weight. The health of the animal is always paramount and Joy’s breeding prospects are secondary to her well-being (which is a shame as she is the nicest looking Gila of the bunch). I spoke with some knowledgeable friends and read through some of my old reptile veterinary books to see if I could get some guidance but ultimately decided that a trip to the vet was the best bet.

The bloody stool Joy excreted shortly after coming into my possession.

Thankfully I live near the University of Florida that has a vet school and accompanying Small Animal Hospital that is willing to see venomous reptiles. I had been there previously to have two Gilas sexed by ultrasound so I knew immediately where to go in this situation. The doctor that worked with us was the same one that helped with the ultrasound and she was very knowledgeable about reptile diseases. There was the a full course of options including ultrasounds and surgery but I opted for the basics with the idea we would move forward with testing as necessary until she improved. The end result of the initial visit was that I had some medicine to give at home; Flagyl every other day for two weeks and intramuscular shots of Amikacin for a month. If this didn’t work we would move on to the second round of testing and medications.

Giving the medicine wasn’t too tough, but you must always take care when handling Gila monsters. At first Joy sadly did not put up much of a fight when I force fed her the dose of Flagly and gave her the Amikacin shot, but within a week she was improving and after the second week she started to eat again! As of today, she has gained over 30 grams of weight and is eating well. I am nervous the sickness may come back so am trying to keep her stress level to a minimum and for certain breeding is off for this year.

The moral of this story is don’t wait too long to seek help in ensuring the health of your pets, and have a vet set up before a crisis occurs. Reptiles are stoic animals and normally do not show weakness until is is too late. If you think your Gila is sick, keep a close eye on their behavior and track the weight (hopefully you have done this since day one, or at least took an initial weight to see where things go). Check with a vet if things aren’t trending well or if the animal refuses food for a few feedings and is losing weight. Always err on the side of caution and your little friend will thank you for many years to come!

Update 2: The deed is done.

After consummating the pairing, the Gilas take a sweet rest together.

Since switching the females to new males a few days ago it’s been more of the same; a lot of chasing but no observed copulation. That is, until last night last night when I woke up around 4:30am to get a drink of water and found one of the pairs in a love tussle. It is a nice hope that the deed is being done in the wee hours of the night where it is dark and secretive. No one has ever, to my knowledge, seen Gila copulate in the wild as the act is normally performed in a shelter out of sight of prying eyes or opportunistic predators. My terrariums are fairly spartan with only a piece of wood, water bowl, and aspen shavings as I like to see the animals (Gilas will hide most of the time if given the opportunity) as well as monitor their health. Perhaps in future years I can provide a hiding area during breeding season but if this set up works I’ll likely stick with it. Maybe I should set up some CCTV cameras on the cages to see what happens when? Now that I have officially observed copulation my confidence level that I will at least get eggs has risen dramatically. Now, whether or not the eggs will be fertile or viable to full term is a whole different story!

An interesting find

Photo by R. Repp

Thought I would share this article about a construction crew that unearthed a Gila monster nest in Tucson, Arizona, which shed some much needed light on when Gilas hatch in the wild. This discovery launched a scientific paper which is also linked for your reading pleasure.

Update 1: Gila monster breeding, thus far.


After keeping Gila monsters for over twenty years and having a lifelong fascination with these amazing reptiles, my first earnest attempt at breeding them has been quite fun. Don’t know how successful at this point, but it’s the journey and not the destination in my case (though seeing baby monsters pip out of the egg would be a dream come true for me).

When studying up on breeding all these years there were so many questions I had. Can you tell a male from female by head shape or appearance? Why do you need a group or colony to breed? What does male combat look like versus male to female interactions? Is it better to keep them singly or in a group when attempting to breed? So far, I have learned a better understanding of these questions and will make an attempt at answering them to the best of my knowledge at this point.

To establish a base point, and long before this breeding season, I have collected as many books on Heloderma as I could (not to mention art, toys, and other chachkies). In relation to breeding, a few books have been the guiding light to my program. First and foremost is Dr. Mark Seward’s Gila Monster Propagation. Despite being one hell of a nice guy that has answered my random emails and questions for over 20 years, his book remains to be the most thorough and introspective writing on the subject. The focus on applying the natural process of wild Gilas to captive breeding is the obvious key to success, and the one I am closely following now. Amazingly, a PDF version of the book is free on Mark Seward’s website here. Of course I’m a dork and have the first and second edition in print:) The other book I am using is a European text, called Beaded Lizards & Gila Monsters Captive Care & Husbandry by Bernd Eidenmüller and Manfred Reisinger. This is another great book that offers insight and some different perspectives into breeding and maintaining Heloderma. I’ve never heard of a Grumbach incubator before reading this book, and liked what I read about the stability of the incubator so I picked up a used one off eBay (Compact S84), tested, modified, and tested again to get the temperature and humidity right. Fingers crossed I get viable eggs to go in this wonderful machine! The other book I am utilizing right now is the venerable Biology of Gila Monsters and Beaded Lizards by Daniel Beck. There is not a specific focus on captive breeding but it does provide invaluable reference to the natural biology and behavior of Gila monsters that can be applied to breeding and has given me a lot of thought on what has occurred so far.

After acquiring the group of adult Gilas, and having the two existing adult Gilas properly cooled to a chilly 53F in a modified wine cooler from Thanksgiving to March 1st, I was good to go. Unfortunately one of my females had some blood in her stool and was ultimately brought to a vet and has been receiving medicine (this experience will be another post soon), she is out of breeding for the year to ensure she is healthy. Always, the well-being of the animal must be first priority! I jumped the gun and started putting my Gila together about the middle of March (April 1st is the recommendation from M. Seward, or 4-6 weeks out of hibernation) to see who was who. I had a good guess on how the sexing game would play out as the head shape on the animals I have were apparent side by side. Two were questionable, but my guesses were accurate. I started by rotating the new Gilas with my 21-year-old, known sexed by ultrasound male and recording the interactions. I started with the Gila that was voted most likely to be a girl with my male. Then paired the most likely male to my male, again recording the interaction. One of those interactions was posted here, and I will put up a female to male video up soon.

Boys will be boys….

Female on the left, male on the right. Can you tell the difference?

The interactions between the sexes is stark to say the least. Males, when faced with another male, reacted almost immediately and the ritualized male combat started. I can see where, when faced with no path of escape, the fighting can escalate to a vicious brawl and continue to the exclusion of breeding. It is intense! After safely removing the “losing” male, or the one that leaves the cage, the remaining male roams around huffing and puffing ensuring the competition has left. Interestingly, both males, the winner and the loser in their respective cages, start raising the tails and marking their territory with their cloaca. At one point, the winner had his hemipenis everted and he rubbed it about his cage. I then introduced a female into the cage. The interaction between males and females in my group could best be described as gentle, even romantic (in lizard terms) as both sexes start licking the air madly, picking up on the scent of the opposite sex. They then approached each other and continued tasting the air and each other with their tongues. It is a much slower pace than the instant male to male interaction, and eventually the male starts to chase the female around the cage in an attempt to copulate.

The pair has settled in nicely. Again, can you tell which is which?

No Means No!

Even in the animal kingdom, no means no. In my case, the females that have been introduced into male cages have been, to my observations, not ready or unwilling to copulate. Did I introduce them to early? Have I somehow missed the short window that the female produces mature follicles? Time will tell at this point as I have not witnessed copulation in my group. The females, when, um, mounted by the males either run away and hiss or bite the male and then run away. But, after the initial night’s excitement the Gilas seem to pair up and are close to each other when resting or lounging around the terrarium. The Gilas are more active at night, and perhaps this is when copulation is taking place but as of right now I cannot know for sure. I did break out my old night vision monocular the other night to observe the pairs but saw more of the same; the females running from the males when approached. I kept the pairs together for a week and have rotated the females to different male’s cages in hopes there will be some compatibility between the pairs.

Q & A

So, I asked a few questions above that I will attempt to provide answers for based on my interpretation of what has happened with my Gilas. Please keep in mind that this is still new to me and I am answering on observations made in my group of Gilas. If different revelations or findings occur, these answers will be updated.

Q – Can you tell a male from female by head shape or appearance?

A – Yes and no. When I had only two Gilas and no idea of their sex there was no known commodity for each and no basis for comparison. If you buy or own a single Gila and do not have a friend with a colony or some known sexed animals I do not think an accurate determination could be made. When I bought the colony, it still wasn’t apparent who was who, but after a few days and taking measurements I made an uneducated guess based on this factor. By sheer luck I turned out to be right but still had to put them together to be 100% sure. Check the photo above and see if you can tell the difference. Not too easy, huh? I plan on doing other comparisons of the sexes on a future post.

Q – Why do you need a group or colony to breed?

A – While I cannot definitively answer this, it appears that the social structure of Gila monsters lends itself well to groups than single pairs. I am sure offspring can be had from just one pair, but I do not know how successful breeding would be overall. I do not think if I had just one pair at this point my chances would be that good. All successful Gila breeders I have spoken with recommend group breeding.

Q- What does male combat look like versus male to female interactions?

A – Male combat is a contest where the fighters engage each other head on, and aggressively. Male to female is overall a more gentle approach. Check out my YouTube channel to see the different interactions between my lizards.

Q – Is it better to keep them singly or in a group when attempting to breed?

A – From a maintenance standpoint, I believe keeping Gilas separately is the best way to go. If the one Gila that is sick was contagious, she may have spread it to the colony and my breeding hopes would have been dashed for the year and some of the Gilas may have died. Not to mention the vet bills increasing exponentially! Also, if a lizard has an issue or isn’t eating it is easier to tell when housed singly. For my breeding program I like to see how each Heloderma suspectum reacts to one another.

I will keep updating this blog as time goes, and feel free to email me with any questions or comments especially if you have successfully bred Gila monsters and can give some guidance.

Thanks for stopping by Goatsby’s Place!


Male combat in captive Gila monsters

Breeding season is upon me, and it couldn’t be more exciting! As this is my first time working with a group of Gila monsters, I was unsure of what male-to-male combat looked like versus male-to-female interactions. In books they look similar but from what I have seen so far it is a very different interaction. Now, I must say that my intention was not to stimulate breeding but to confirm the sexes of the lizards in my colony. I have read that male combat can be vicious in captivity as there is no escape for the subordinate male and can certainly see how it can escalate to this level after seeing my males briefly duke it out. I find it interesting that males do not waste time getting into combat when introduced to one another, while males and females take some time to find each other and the ensuing interaction is much more gentle (though, I have seen the females bite the males on several occasions so far). This is the first step in breeding, and has been very interesting to see these reptiles interact.

Below are a few videos shot on my Leica X Vario to help others see what male combat looks like in captivity. Please note that I was around the whole time during this interaction to ensure things did not get out of control. There was some biting in the beginning but it turned into a wresting match.