For most mammals, piloerection is a common method of modifying heat exchange. It is caused by the contraction of the musculi arrectores pilorum or MAP, which are bodies of smooth muscle that extend from the fibrils of the dermis into connective tissue investment of the hair follicle.

How does piloerection keep you warm?

Piloerection (goosebumps).

In response to increased sympathetic nerve discharge, the arrector pili muscles at the base of tiny hairs in the skin contract and cause the hairs to become upright, trapping air and thus increasing the insulating layer of air around the body and minimizing heat loss.

What is piloerection in animals?

Piloerection is the raised hairs on the shoulders, along the back and (sometimes) the tail. This is most commonly seen on dogs or cats, but it has been observed in other animals such as birds, rats and many more. This hair-raising reaction is involuntary and a result of the nervous system.