Why do Arctic foxes have smaller ears than desert foxes?

Arctic foxes have smaller ears than desert foxes as an adaptation to their cold environment. This difference is explained by Allen's rule, a zoological principle stating that protruding body parts—such as ears, tails, and limbs—are relatively shorter in animals living in cooler climates compared to those in warmer regions.12

In cold environments, smaller ears help minimize the surface area through which body heat can be lost, aiding in thermoregulation and the conservation of warmth. Conversely, desert-dwelling foxes, such as the fennec, possess large ears that facilitate the dissipation of excess body heat into the environment, helping them maintain an optimal internal temperature in hot climates.134