This is a period of torpor that lasts for a whole season. During torpor, an animal reduces its body temperature. It also decreases its bodily activities. This is a good way for an animal to save energy that it might otherwise use keeping warm and finding food. Torpor can be a short as a single night. But when it goes on for a long time — such as an entire winter — scientists call it hibernation.
In a sentence
The deadly white nose syndrome hits bats while they hibernate — when their low body temperatures make it easier for the fungus that causes the disease to spread.