Cold Weather Care
Desert tortoises should be kept outdoors all year in Arizona. As the weather turns cool in the fall, a tortoise will prepare to hibernate in its burrow. Its appetite and activity level will decrease.  It will have a fat reserve built up, and it should easily survive winter hibernation if it has eaten well during the warm months. A health check-up with a reptile veterinarian is recommended in the fall to make sure your tortoise is healthy enough to hibernate. 

If a tortoise does not move into its burrow by the time temperatures at night go below 50° F, or you are not sure the burrow will remain dry during winter rains, you will need to hibernate your tortoise inside.  The tortoise should be placed in a cool, dark area such as a garage. A heavy cardboard box or plastic storage container packed with shredded paper or straw generally provides adequate protection. The box should be covered with several layers of blankets or newspapers, and it should be kept up off the floor away from any holes that could lead to drafts or rodent invasion. The temperature should remain around 55° F.  Dehydration is a significant risk during hibernation, but it can generally be avoided if the humidity is maintained between 30-40 percent.  These parameters can be monitored using an inexpensive thermometer and humidity meter.  Juveniles should be offered water every 2-3 weeks, and adults need water every 4-6 weeks during hibernation. Quietly check on the tortoise weekly to ensure that no health problems are developing. Otherwise, do not expose the tortoise to light or other disturbances.

Dehydration is a significant risk during hibernation, even if your torotise hibernates outside in its burrow. Before your tortoise retreats to hibernation, you may soak it for 20 minutes; be sure to dry your tortoise completely before it heads into its burrow and it begins hibernation.  If you have more than one tortoise, soak them separately so you avoid spreading diseases.  if it is a dry winter, you should supplement waterby recreating a winter rain.  On a warm (~65° F or above) overcast day, you can turn on a sprinkler within 10 ft. of the burrow, which may prompted the tortoise to come out and drink.

It is a good idea to have your tortoise's health evaluated in September to make sure it is healthy enough to hibernate.  If it is not, or it weighs less than 20 grams, you should bring the tortoise inside and keep it in an indoor enclosure (at least 3 ft. by 3 ft.) filled with a one-quarter to one-half inch diameter gravel substrate.  Sand and fine gravel should be avoided since it may be accidentally ingested, causing fecal impaction and gastrointestinal infections.  The daytime temperature should be kept at 80-85° F with a nighttime range of 68-75° F.  The ideal temperature can be achieved with an artificial light above the enclosure and by installing a thermometer inside. Artificial lights should mimic a normal daily photoperiod, so they should be turned off at sunset to help prevent hyperthyroidism, a glandular disorder. The ideal light cycle is an 11 hour day cycle followed by a 13 hour night cycle, preferably using a mercury vapor light, which provides full spectrum lighting and heat.  The enclosure should have a shelter box, which will provide relief from the heat and prevent dehydration.  The tortoise should be fed according to the summer feeding schedule and needs fresh water at least three times a week.  Natural sunlight is beneficial to tortoises in rehabilitation as it will usually stimulate their appetite.  Tortoises can go outside on sunny days with a temperature above 70° F. They should still be given access to shade.

As spring approaches, a hibernating tortoise will become more active. Once the tortoise emerges, provide shallow puddles of lukewarm drinking water. The tortoise will gradually resume its warm weather routine of eating, basking and exercise. Tortoises maintained in southern Arizona are usually active by April, but in particularly dry years, they may not emerge until the summer rains begin in July or August.