A single female harvest mouse can have up to seven litters in a single year. Each litter can contain as many as 12 baby mice each.
Eagles built the biggest nests of any birds.
The nests are called eyries and are made from piles of sticks and twigs. Some eyries are as large as a small car!
In the winter, a female polar bear digs a hole in the snow where she will give birth and live through the coldest months. Male polar bears on the other hand do not have homes.
They are constantly on the move looking for food.