Guidelines for Turtle/Tortoise Hibernation
Commonly kept species that will try to hibernate: Desert tortoises (Gopherus); Russian tortoise (T. horsfieldii); Box turtles; Wood turtles (Clemmys insculpta); Spotted turtles (Clemmys guttata); Snapping turtles (illegal/protected in several states); and Red-eared sliders (Trachemys scripta elegans).
Hibernation protects cold-blooded creatures (and some warm-blooded) in cold weather or when food and water are scarce.
Dormancy also affects the reproductive cycles of chelonian species. A “cooling period” stimulates breeding activity when temperatures normalize. On this info sheet turtles and tortoises are divided into only two categories: non-tropical (species that hibernate), and tropical (do not hibernate).
Turtles and tortoises can hibernate up to a full eight months of the year, depending upon latitudinal location. The rule-of-thumb to guide you on your research should be: The farther from the equator the species occurs naturally, the more likely it is to hibernate; the closer to the equator, the less likely.
If you have recently acquired an animal, have one that is ill or recovering, or a hatchling that is under three years old, do not hibernate them; this group is highly vulnerable to dying if allowed to hibernate.
Turtles and tortoises usually instinctively stop eating on their own before hibernation, but it’s best to ensure that they do through regulation of food availability. Omnivorous species must be kept from feeding at least two weeks prior to hibernation (to avoid food fermentation in the stomach and risk of death). Fruit is especially dangerous.
Hibernating Terrestrials And Semi-Aquatics (Inside And Outside)
The two biggest hazards are freezing and drowning for hibernation outdoors, so it is best to provide containers in which the pet can spend the winters inside. A box-within-a-box that filled with wadded or shredded newspaper provides insulation and darkness. This box can be placed in a secluded room, closet, a shed or a garage. A thermometer needs to be kept on the box. This must be checked frequently, especially if there are external weather changes.
Hibernating species can generally tolerate a temperature between 39°F and 50°F (3.8°C and 10°C). Above 50°F may precipitate torpor, not a true hibernation, and your pet may use up precious fat reserves due to a raised metabolism. If that happens you’ll have to take the turtle or tortoise out of its hibernation box and allow it to gradually come increase to a warmer temperature. The animal must then be fed and maintained at non-hibernation temps. This scenario is likely if your tortoise is active in its hibernation box or if you find urination/waste. Remove your pet, hydrate it and move the box to a cooler, protected spot. Provide fresh, dry substrate and monitor to be sure hibernation is taking place.
It’s critical to weigh your pet prior to hibernation and chart the weight throughout the hibernation period. Buy a digital gram scale for weighing the smaller species. Ask your vet or herpetologist what amount of loss is considered acceptable based on your pets size. In general a tortoise or turtle should lose only 1% of its body weight per month during hibernation. Chart it the weight on a piece of paper you keep taped near to the hibernaculum/container and keep it as a guide for the following year’s hibernation. If you are unsure about the amount of weight loss, ask your vet.
Captive turtles/tortoises that are being hibernated in unnatural conditions risk dehydration due to low humidity. Nonetheless, they mustn’t be allowed to become wet and chilled. Check the skin condition regularly. If the skin is drier than normal (usual) or the animal has lost too much body mass during that period, wake it slowly and soak it in shallow (below the bridge) room-temperature water for two hours to regain its lost fluid. Dry it thoroughly (but do not warm it!) and return it to its box. Younger tortoises and turtles (hatchlings and juveniles) should have this done every three weeks regardless.
Turtles and tortoises store more body water in the fall than the summer, so hydration is critical to a successful outcome. If your hibernating turtle or tortoise voids its water stores (you find the bedding/substrate is wet), you MUST bring it out for rehydration.
If your animal is to be hibernated outdoors, make sure it has access to drinking water at all times, but don’t let it hibernate in a location where rain can drown it or get it wet enough to cause chilling. Check the hibernation spot frequently. If you see a turtle or tortoise out trying to bask on a rainy or cloudy day, it may be a sign that something’s wrong with the hibernation process. Bring the animal indoors and examine it to see if hibernation should be allowed to continue. Consult with your vet if you are unsure. Better safe than sorry!
Attention to detail makes the difference between a successful hibernation and potentially death. You will need several tools to help with your task: a gram scale, thermometer, humidity gauge, and resources such as the local tortoise club, and an exotics veterinarian.