Runt

In a group of animals (usually a litter of animals born in multiple births), a runt is a member which is smaller or weaker than the others. Due to its small size, a runt in a litter faces obvious disadvantages, including difficulties with competing with its siblings for survival and possible rejection from its mother. Also in a domestic dog litter, most puppies would have to make room for the runt to get milk from the mother. Therefore, in the wild, a runt is less likely to survive infancy.