Hibernation is part of the natural cycle of the Sonoran desert tortoise.  As the day length shortens and cooler weather begins in the fall, desert tortoises stop feeding and seek out shelters (hibernacula) to protect them from the cold winter weather.  Since the desert tortoise is unable to generate its own body heat, when the temperature around it falls, its metabolism slows.  Feeding stops during hibernation because the tortoise is no longer able to properly digest it’s food and is no longer using the same amount of energy it does during warm weather.  A tortoise may emerge from its burrow on sunny winter days to bask briefly or drink water if it is available after a winter rain, but will return quickly to it’s shelter to prevent exposure to cold night time temperatures.

Hibernation is an important part of desert tortoises’ normal physiology. Desert tortoises will often become unhealthy if they are not allowed to hibernate for several years so we strongly recommend that the pet desert tortoises are hibernated unless they have serious medical conditions.

Pet desert tortoises may hibernate either in an appropriate outdoor hibernaculum, such as a properly constructed artificial burrow, or in insulated boxes kept in a cool room of the house where the temperature stays between 50 and 65°F. It is usually best to allow desert tortoises to hibernate outside in their burrow when possible. Outdoor burrows need to be constructed in ways that insulate tortoises from the cold and also prevent them from getting wet. Make sure that there is enough substrate over the burrow to prevent moisture from seeping in and that they are constructed in ways that prevent flooding during winter rains.

A desert tortoise will start slowing down in late September and early October when the nights begin to cool into the 60s (°F) and the daylight hours decrease.  Hibernation usually starts in mid to late October when the night-time temperatures drop in the low 60s (°F) and the days no longer are hot.  Stop feeding your tortoise any supplemental produce for 3-4 weeks before hibernation so that undigested produce does not cause problems when your tortoise cools down.  Soak your tortoise in shallow water during the month prior to hibernation so that has an opportunity to drink to prior to hibernation.  The soaking will also stimulate defecation to help empty its intestines.

When hibernation outside is not an option, place your tortoise inside in an insulated box and keep him in a part of the house or garage that stays between 50 and 65°F.  If it is much warmer, your tortoise may be too active and will lose weight.  If it drops much below 40°F, your tortoise runs the risk of damage from the cold temperatures.  Check your tortoise periodically.  Soak it in room temperature water about once every 4-6 weeks since the hibernating box is much drier than a natural hibernaculum. Your tortoise will need to hibernate for a few months, typically between 2 and 4 months.  If the temperature is much above 65°F, the desert tortoise may be active and use up its energy stores too quickly.  If the temperature is much colder, the desert tortoise may develop health problems. Once the overnight temperatures are getting above 65°F and there are warm (85°F) sunny days, your tortoise can be removed from hibernation and placed back into the outside enclosure.

A desert tortoise has to be healthy to survive the rigors of hibernation. If a desert tortoise lacks sufficient body fat or is ill  going into hibernation, it may die during this time or emerge in the spring so debilitated it is unable to regain its health. Ill desert tortoises will often come out of their burrows and attempt to warm themselves, even on cold days. If you notice your tortoise is spending a lot of time out of the burrow during cold weather, or if eyes are becoming crusty, a runny nose or a thick snotty nose develops, or weight, bring it out of hibernation and schedule an exam as soon as possible.

We strongly recommend an annual pre-hibernation exam between late August and mid September to ensure that your desert tortoise is healthy and ready for hibernation.

copyright 2009
Kevin Wright DVM and Jay Johnson DVM
Arizona Exotic Animal Hospital
744 N Center Street
Mesa, AZ 85201
info@azeah.com
www.azeah.com