Gila Monster Breeding Preparation


Beyond the nutritional requirements for general husbandry, special attention needs to be paid to feeding in preparation for reproduction. Egg production requires a huge energy investment for a female Gila monster. The frequency and quantity of food offered to a female becomes critical to successfully prepare her for reproductive cycling.

If a female does not have adequate fat reserves, she cannot reproduce—it’s that simple. Since preparation for reproductive cycling in Gilas begins well before the winter cooling period, the amount of food offered the year before breeding becomes critical also.

After egg laying I feed females twice a week as much as they will eat to regain their pre-egg laying weight. I also feed them heavily once they emerge from winter cooling.

If the nutritional requirements of captive female Gilas are managed appropriately, they are capable of producing eggs on a yearly basis.


Time-lapse monitoring of winter shelter, Pinal County, Arizona.
A time-lapse camera monitors the winter shelter of a Gila monster, Pinal County, Arizona.

In many vertebrates, including reptiles, after breeding there is a "refractoriness" to light and temperature stimulation. In other words, under conditions of light or temperature that would normally stimulate the reproductive system no stimulation occurs. A period of short days or cold temperatures is required to break this refractoriness and regain sensitivity to the conditions of light or temperature that will stimulate the reproductive system. In Gila monsters, this can be accomplished by cooling them in the winter.

Most recommendations involve a three-month cooling period with temperatures of 13 to 14 C (55 to 57 F). This is typically from the first of December to the first of March. It is important to suspend feeding at least two weeks prior to cooling to allow for full digestion of their last meal prior to cooling. Hibernation is begun by slowly decreasing the temperature until the final cooling temperature is reached. Then in the spring, the temperatures are slowing brought back up.

There are numerous ways to accomplish this winter cooling period. In my colony, the temperatures in my Gila room are brought down automatically to mimic the temperatures of their shelters in the wild. A computer controller manages the temperature changes.

Water should be available during hibernation both for drinking and to increase the humidity of their hibernating environment. Provide it in a container that can’t be easily tipped over. I feel it is important to provide adequate humidity during hibernation to prevent dehydration of the animals. Dehydration is a particular risk to younger, smaller animals.