Complex sentence: Normally when colder conditions arrive, animals go into a state of suspended animation called hibernation, when they go into a state of inactivity for long periods of time, which they do not come out of until more suitable conditions for them to survive in arrive.
Split into simpler sentences: Normally when colder conditions arrive animals would go into a state of suspended animation called hibernation. This is when an animal goes into a state of inactivity for long periods of time, which they do not come out of until more suitable conditions for them to survive in arrive.