Hedgehogs are instantly recognizable by their dense coat of spines, but their behavior varies greatly depending on their species and environment. Whether a hedgehog hibernates depends entirely on if the animal lives in the wild or is kept as a pet. Wild hedgehogs from temperate regions have a natural, sophisticated process for surviving winter. However, their captive counterparts, mostly originating from warmer climates, do not share this survival mechanism. Understanding this difference is important for anyone who encounters a hedgehog.
The Biology of Hibernation in Wild Hedgehogs
True hibernation is a profound physiological adjustment found in certain temperate species, such as the European hedgehog (Erinaceus europaeus). This state allows the animal to survive when food is scarce and temperatures are consistently low, typically below 10°C (50°F) for extended periods. The process is characterized by a drastic suppression of the hedgehog’s metabolism to conserve energy reserves.
A healthy, active European hedgehog maintains a body temperature around 35°C (95°F), but during hibernation, this temperature can plummet to as low as 2°C to 5°C (36°F to 41°F). This cooling is accompanied by a severe reduction in heart rate, which slows from an average of 190 beats per minute to a mere 20 beats per minute. Breathing also becomes extremely slow and shallow.
To sustain this deep sleep, wild hibernators must prepare for weeks by accumulating significant fat reserves, with fat making up about 30% of their body weight before hibernation. These reserves include white fat, which provides a constant energy supply, and brown fat, concentrated around the shoulders and chest. Brown fat is important because it is rapidly metabolized to generate heat during periodic arousals, which are necessary to prevent the body from freezing.
Species Differences and the Danger of Pet Hedgehog Torpor
The domesticated pet hedgehog is most commonly the African Pygmy Hedgehog, a hybrid primarily involving the Four-toed Hedgehog (Atelerix albiventris), which originates from the warm, central regions of Africa. Unlike their European cousins, these tropical species never evolved the specialized physiological mechanisms required for safe, sustained hibernation. The pet hedgehog’s body cannot accumulate the necessary brown fat reserves or control the slow metabolic changes needed for true hibernation.
When a captive African Pygmy Hedgehog is exposed to low ambient temperatures, typically falling below 22°C (72°F), it may attempt to enter a state known as torpor. Torpor is a short-term, involuntary response to severe environmental stress, such as cold or lack of food. This state is profoundly different from planned hibernation. This uncontrolled reduction in body temperature and metabolism is extremely dangerous for the pet species.
Because they lack the proper adaptations, a hedgehog in accidental torpor is at high risk for fatal complications, including dehydration, organ failure, and respiratory infections, such as pneumonia. Instead of entering a protective state, the animal enters a metabolic crash that can be lethal within a short period. Therefore, while the wild European hedgehog hibernates as a survival strategy, the pet African Pygmy Hedgehog attempts torpor as a life-threatening malfunction.
Recognizing and Preventing Accidental Torpor in Captive Hedgehogs
Pet owners must be vigilant to prevent the onset of accidental torpor, which is the greatest environmental threat to a captive hedgehog. The most important preventative measure is maintaining a constant, warm environment. The ambient cage temperature should ideally be kept between 24°C and 27°C (75°F and 80°F) at all times. A drop below 18°C (65°F) for any length of time can trigger a dangerous attempt at torpor.
Physical signs that a captive hedgehog is attempting torpor include a noticeably cold belly, lethargy, and a reluctance to uncurl from a tight ball. The animal may also display a wobbly or shaky gait if it tries to move, show irregular breathing, or become unresponsive to handling. Loss of appetite and thirst are also early warning signs that the hedgehog’s systems are slowing down.
If torpor is suspected, immediate action is required to slowly and gently raise the animal’s body temperature. This can be accomplished by holding the hedgehog against a person’s bare skin inside a shirt or wrapping it in a towel warmed lightly from a dryer. Warming must be gradual to prevent the animal from going into shock, so owners should never use hot water or place the hedgehog on an extremely high-heat source. Once the hedgehog’s belly feels warm and it is fully alert, offering lukewarm water and soft food can aid in recovery, though veterinary attention should follow any torpor event due to the risk of internal damage.