The burrow serves a critical function in protecting a tortoise from the extreme heat and aridity of the summer, and providing a place to hibernate in the winter, so it is important that the burrow insulates well. Burrows can be incorporated into the existing landscaping as a focal point of the yard or they can be inconspicuous, depending upon preference. Burrows should have at least 8 inches of soil on top, and should have a soil bottom (no rock or gravel) for insulation from the cold and heat. Avoid making the burrow too roomy. In the wild, desert tortoises prefer snug burrows where they can wedge themselves into a corner near the back.
Since a burrow provides protection in both the summer and winter, it is important to consider the entrance’s orientation (the cardinal direction the burrow entrance is facing) when building it. North and northeast facing burrows tend to be cooler, and provide good refuge from the summer heat. The optimal temperature range for a burrow during the summer is 68 to 85° F. The temperature should be kept below 90° F to prevent the tortoise from overheating and suffering brain damage. During mild weather, tortoises may dig a shallow depression (pallet) in the soil, usually beneath a shrub or other low-growing vegetation for shelter from the sun. South facing burrows warm up quicker than north facing burrows, and offer a suitable shelter for winter hibernation (hibernaculum). Providing more than one burrow gives the tortoise the option to choose a burrow based on the temperature and time of year. An ideal enclosure would contain multiple burrows with different orientations for each season, but a single burrow will suffice if it is strategically placed. If only one burrow is constructed, place it in the shade of a shrub or tree.
The burrow should be high and dry and placed in an area of the yard away from any water source, including irrigation and any areas where water puddles. The burrow should be built on a flattened mound of dirt (8 inches high), which will protect the burrow from runoff. If the yard has irrigation or is flood irrigated, it is critical that the tortoise burrow stay completely dry. The tortoise should also have a dry place to bask at least 8 feet away from the water and raised up 1.5 feet above ground. A damp burrow can make a tortoise susceptible to various respiratory ailments that require costly veterinarian treatment. These ailments are often fatal to the tortoise if left untreated. It is especially important that the burrow remain dry during winter, when a hibernating tortoise can easily drown if the burrow fills with water.
Burrow construction materials should be strong enough to support the weight of the dirt insulation on the top of the burrow, and durable enough to last a long time. Wood is not an ideal material because it will not last the life of a tortoise with Arizona’s dry air and termites. If wood is used for the roof of a cinder block burrow, use at least two or three layers of three-quarter inch plywood.
The type of burrow provided for a tortoise will depend on location due to the different climate conditions found throughout the state. In Phoenix or Tucson, the burrow should be built above ground because greater rainfall increases the likelihood of flooding. Detailed instructions and photos for creating burrows in Phoenix and Tucson can be found here.
In Bullhead City, Kingman, Lake Havasu, or Yuma, burrows should be dug below ground to offer the best thermal protection from the extreme heat in these regions, and it should have an eave to keep rain from falling in. However, it should still be built in a high area of the enclosure to prevent flooding during heavy rain. Detailed instructions and photos for creating burrows in Bullhead City, Lake Havasu, Kingman, and Yuma can be found here.