What adaptations enable mammals to live in a polar environment?
MacPhee: One of the main ways that mammals adapt to the polar regions is through mechanisms providing insulation, such as fur, blubber, and an efficient circulatory system. For marine mammals, insulation is less of a problem than you may think. As long as they’re in water that’s not frozen at 32 degrees Fahrenheit [0 degrees Celsius], a few inches of blubber and fur patterning that is high in R-value [thermal resistance] are sufficient insulation to keep them warm. On land, the extreme temperatures require that animals have other adaptations, one of the most significant ones being hibernation. Some mammals go into a true deep sleep while others go into what is known as estivation, reducing their activity in order to save their energy. For example, female polar bears give birth while they hibernate. They dig a cave in the snow and stay there until their pups are born, providing a warm enclosure for them and reducing any need to depart from their pups into the early stages of their devel
