What does Allen's Rule state regarding mammals living in cold climates?

Allen's Rule specifically addresses the physical adaptations of mammals to cold environments. It posits that mammals residing in colder climates tend to exhibit shorter faces and limbs compared to their counterparts in warmer climates. This adaptation is thought to minimize heat loss by reducing the surface area exposed to the cold.

In cold environments, shorter extremities help retain body heat, which is essential for survival in harsh temperatures. Thus, mammals that have adapted to these conditions show these characteristics as a means of thermoregulation.

While other factors, such as fur thickness and overall body size, can also play roles in how mammals survive in cold climates, Allen's Rule specifically focuses on the proportions of limbs and facial structures as they relate to temperature adaptations.