Most Mediterranean tortoise species hibernate, along with Horsfield’s (Russian) tortoises and North American desert tortoises. Tropical and subtropical species, including Sulcatas, Leopard tortoises, Red-foots, and Yellow-foots, do not hibernate and can become seriously ill if exposed to hibernation temperatures. Knowing which group your tortoise falls into is one of the most important parts of keeping it healthy through winter.
Species That Hibernate
The tortoises that naturally hibernate come from climates with cold winters, where food disappears for months at a time. These species have evolved the metabolic machinery to slow their bodies down and survive on stored energy. The main groups are:
- Hermann’s tortoise (both Eastern and Western subspecies)
- Spur-thighed tortoise (Greek tortoise, northern populations)
- Marginated tortoise
- Horsfield’s tortoise (Russian tortoise)
- North American desert tortoise (Gopherus agassizii)
For these species, hibernation isn’t optional. It plays a role in regulating hormones, maintaining long-term health, and supporting normal breeding cycles. Keepers who skip hibernation for healthy individuals of these species often see behavioral and reproductive problems over time.
Species That Should Never Hibernate
Tropical tortoises come from regions where temperatures stay warm year-round. They have no biological adaptation for cold dormancy, and forcing hibernation on them risks organ failure, respiratory infection, and death. According to Royal Veterinary College guidelines, the following species should never be hibernated:
- Leopard tortoise
- African spurred tortoise (Sulcata)
- Red-footed tortoise
- Yellow-footed tortoise
- Egyptian tortoise
- Southern Turkish spur-thighed tortoise
- Libyan and Tunisian tortoise variants
These species need to be “overwintered” indoors with heat and UV lighting that mimics their natural habitat. If you own a Sulcata or Leopard tortoise, your job during winter is to keep temperatures up, not let them drop.
What Happens Inside a Hibernating Tortoise
Tortoise hibernation is technically called brumation, because reptiles don’t enter the same deep unconscious sleep that mammals do. A brumating tortoise remains faintly aware of its surroundings and may shift position occasionally, but its body slows to a near standstill.
Metabolic rate drops dramatically as body temperature falls. For every 10°C decrease in temperature, a reptile’s metabolism typically drops by two to three times. Below 10°C, this effect becomes even more extreme. Heart rate can slow to one beat every two to three minutes, and in some cases as few as one beat every five to ten minutes. Blood pressure drops to a fraction of normal levels. The tortoise’s cells coordinate a shutdown of both energy production and energy consumption, keeping everything in balance so the animal doesn’t burn through its reserves or accumulate dangerous waste products.
Despite this profound slowdown, the tortoise does still produce small amounts of lactic acid and other metabolic byproducts. After three to five months of dormancy, lactate levels in the blood can climb significantly. This is one reason hibernation can’t go on indefinitely, and why duration matters.
How Russian Tortoises Hibernate in the Wild
Horsfield’s tortoises offer a useful window into what natural hibernation looks like. In the wild and in outdoor captive settings, these tortoises dig long tunnels to prepare for winter. Measured burrows have reached 52 cm in length. At the end of the tunnel, the tortoise excavates a small chamber, turns around, and positions itself at a slight upward angle with its head facing up.
Hibernation typically runs from late autumn through early March. Emergence happens gradually over about two weeks, with the earliest risers appearing around early March and the last ones surfacing by mid-March. This staggered waking is normal and reflects individual variation in metabolism and burrow temperature.
Safe Temperature Range
The ideal hibernation temperature for tortoises is around 5°C (41°F), with a safe range of 2 to 10°C (roughly 36 to 50°F). Temperatures above 10°C are problematic because the tortoise’s metabolism stays high enough to burn through fat reserves too quickly, but the animal isn’t alert enough to eat. Temperatures below freezing risk ice crystal formation in tissues, which can be fatal.
If you’re hibernating a tortoise in a fridge, garage, or outbuilding, a reliable thermometer with a minimum/maximum reading is essential. Insulating the hibernation box helps buffer short-term temperature swings but won’t prevent freezing if ambient temperatures drop below zero for any sustained period.
Checking if Your Tortoise Is Fit to Hibernate
Not every individual of a hibernating species should actually hibernate in a given year. Any tortoise that is underweight, sick, or recovering from illness should be overwintered indoors with supplemental heat instead.
The standard tool for assessing fitness is the Jackson Ratio, which compares body weight to shell length. The formula is: weight in grams, multiplied by 100, divided by the straight carapace length in centimeters cubed. If the result falls below the safe range for that species, the tortoise is too light to hibernate safely. If it’s above the range, the tortoise may be overweight, which can also cause complications. The Jackson Ratio is designed for Testudo species (Hermann’s, Greek, and Marginated tortoises) under two kilograms. It doesn’t work well for Horsfield’s tortoises, which have different body proportions.
Preparing for Hibernation
The wind-down period before hibernation is just as important as the hibernation itself. In early October, most tortoises naturally begin eating less. This is the right time to stop offering food: one to two weeks before hibernation for smaller tortoises, and about three weeks for larger ones. During this fasting period, keep temperatures warm (around 24 to 27°C) so the tortoise can fully digest any remaining food in its gut. Undigested food left in the intestines will ferment during hibernation and can cause dangerous infections.
Soaking your tortoise in warm water (around 21 to 24°C) at least three times a week during this period encourages drinking and helps ensure the animal enters hibernation well hydrated. Hydration is critical because tortoises continue to lose small amounts of water through their skin and breathing during brumation, and they can’t drink to replace it.
Waking Up After Hibernation
When a tortoise emerges from hibernation, rehydration is the first priority. Place the tortoise in a shallow warm water bath, with the water level reaching between the bottom of the shell and the chin. Let it soak for about 30 minutes. Tortoises drink through their mouth or nose and can also absorb water through their cloaca. They often urinate during soaking as their body flushes out concentrated waste built up over winter. If the water becomes fouled, replace it with fresh water and continue the soak.
Most tortoises begin eating within a few days of waking, though some take up to a week. Offer easy-to-digest leafy greens and continue daily soaks until the tortoise is eating and drinking normally. A tortoise that refuses food for more than a week after waking, or that appears lethargic with sunken eyes or a runny nose, needs veterinary attention promptly.