A lot of conflicting information has been published regarding the incubation of Gila eggs and many breeders have had difficulties bringing eggs to full term. It is important to consider three factors that affect the environment of the developing Gilas. These factors are temperature, moisture and oxygen tension.

Suggested temperatures for incubating Gila eggs range from 79-85 F. It has been suggested that incubating them over 85 degrees F can result in failures.

I incubate the eggs at 77-80 F—never over 80 F.

Most breeders use vermiculite as an incubating medium, although other substrates have been used. Suggested water-vermiculite ratios range from 1:1 to 1:4 (by weight). I am of the opinion that excessively wet incubation medium is harmful to Gila eggs and is responsible for many failures.

Although Gila eggs should not be exposed to excessive contact moisture, they do need to be exposed to adequate humidity.

In the past, eggs were set up in a relatively dry mix of vermiculite. I would carefully weigh the water and vermiculite to create a ratio of 1:4. The eggs were half buried in the vermiculite with the embryo on the top. Setting up the eggs with the embryo on top allowed me to more easily monitor the growth of the developing Gilas.

With my previous incubation setup, maintaining the proper moisture required the addition of water to the vermiculite many times during the incubation period. I was careful to add water of the same temperature as the incubator to prevent thermal shock to the developing embryos (this was done by keeping a water bottle in the incubator at all times). The humidity in the incubation chamber as well as the amount of ventilation to the incubator and the individual egg containers would affect the rate of water loss. The egg containers were periodically weighed to determine water loss and water was added to compensate. I weighed each container weekly until I got a sense of how much water was lost how frequently. I was careful to not place water directly on the eggs as this has been suggested to contribute to egg death. Eggs exposed to inadequate amounts of moisture will begin to dent. I would occasionally remove the eggs from the incubation medium and remix the substrate to maintain an even distribution of the moisture.

This technique was successful at hatching Gila eggs, but also had it’s problems. It was difficult to maintain stable conditions for the developing eggs. The frequent tinkering required to maintain appropriate moisture levels over the entire four and a half months of incubation was no less than a real pain. For several years I have been experimenting with alternate techniques to incubate Gila monster eggs. I wanted to develop a technique that fulfilled certain criteria. The primary and most obvious goal in creating the new protocol was to create an environment ideally suited to the development of Gila eggs. Equally important, though, was to create a stable environment that needed little attention during the long period of incubation. Additionally, I wanted a technique that was easily reproducible; I wanted anyone to be able to use the technique with success equal to my own.

After many years of trying different materials and different procedures, I have come up with a technique that I believe fulfills all these requirements. I call it the Hygroscopic Incubation Technique. To learn the details about this new incubation technique, see the second edition of Dr. Mark Seward's Gila Monster Propagation. Click here for more information.