Question: Why are some animals nocturnal, and why do they hibernate?

Joanna Cruden answered on 15 Jun 2012:

Nocturnal animals are primarily active at night rather than during daylight hours for all sorts of reasons for example in hotter places such as the tropics, it’s cooler at night. If you’re a bat, then your ancestors took to the night skies to avoid competition for resources from birds.

If you are prey (eg; mouse) it’s easier to hide from predators under cover of darkness but that means your predators (eg; owl) have to come out at night to feed, so the species evolved to become nocturnal.

Animals hibernate in places where winters are harsh and there is little food available, so they eat plenty to store up on body fat and go into a deep sleep where there heartbeat and breathing slow down and they use very little energy.