Otters can be separated into two groups on the basis of their diet. The first group, which includes river otters and giant otters, specializes in eating fish. These species have sharp teeth that are useful in catching and gripping their slippery prey. The second group, which includes the small clawed otters and sea otters, specializes in eating invertebrates such as shellfish. These otters have blunted teeth useful in breaking shells. However, otters are highly adaptive, and neither group solely eats just one type of prey.