Surviving the tugged terrain and hostile weather conditions of the North American Arctic tundra, the Arctic ground squirrel is perhaps the toughest of the Sciuridae family. By disappearing into burrows covered in lichen and muskox hair for almost eight months, they are one of the few Arctic animals that actually hibernate.

During their epic winter lie-in, the squirrels’ core body temperature drops down to -3 degrees Celsius (26.6 degrees Fahrenheit) and its heart rate drops to just one beat per minute. When spring emerges and their body clock awakes, maids heed to protect their territory from rivals and find a mating partner. Females are typically fertile for just, 24 hours, and needy males won’t leave their side during this time. The size of an Arctic ground squirrel varies dramatically depending on the season. They spend the summer months frantically fattening up ahead of their winter hibernation.