Hibernation help: brown and white fat
20th October 2021
In order to survive the cold winter months when natural insect food is scarce, hedgehogs must feed and store as much energy as they can in advance. These energy stores, in the form of body fat, allow them to hit the pause button and hibernate until spring, only rousing periodically. Extra food from people can help to ensure they gain enough weight to last until spring.
Hedgehogs have two types of fat; white and brown. Each of these have different functions during hibernation.
‘White fat’ is the main storage tissue and supplies energy for general body maintenance. Essentially, it keeps the animal alive while it hibernates. During hibernation, a hedgehog will drop it’s body temperature down to around 4◦C, and only breathe a few times a minute. While this serves its function of ensuring the animal’s energy requirements remain low during winter, some fuel in the form of white fat is still required to keep the hedgehog alive. White fat also serves this purpose outside of the hibernation season, essentially storing fuel for the hedgehog to stay alive.
The function of ‘brown fat’ on the other hand is more specific to hibernation, and is used when the hedgehog needs to become active again. This type of fat allows a hedgehog to gradually boost its body back to normal temperature when needed. Brown fat is usually stored around the shoulders of a hedgehog meaning that when required, the heart is warmed first. The heart then circulates heat around the body. Brown fat is also present in the body in the spring and summer but in much smaller quantities.
Why do hedgehogs wake up from hibernation?
Hedgehogs do occasionally rouse in the winter during periods of milder weather in order to forage for food. They can also become active in response to unexpected disturbance. This however can be dangerous for them as hibernation is not sleep and requires a lot of energy to rouse from. To ensure hedgehogs retain these precious energy reserves, be careful of disturbance like loose pets or gardening during winter.
Find out more about hibernation in these FAQs.