What is a Dewlap and why do rabbits have them

A dewlap is a pouch of fat beneath the jaw of a doe (female rabbit), especially if they were not spayed early. The appearance can be anywhere from a small bump under the rabbit's chin, to a large pillow around its neck. Dewlaps are more prominent in large breeds and lop-eared rabbits.

The dewlap tends to appear when a doe has reached the age of reproduction. The dewlap provides a place where she can pull out her own fur and use it to line her nest and keep the babies warm.  Some bucks (male rabbits) also have small dewlaps, but the trait is not common.