Least weasels have a lot of size variation across the species. The body of this species is slender and elongated, with short legs and tail. Color varies by region, along with tail length and pelage type. The Least weasel evolved when northern forests were replaced by open grassland 5–7 million years ago. These small rodents form the largest part of the least weasel’s diet, but it also kills and eats rabbits, other mammals, and occasionally birds, birds’ eggs, fish and frogs.