Mammals of Pennsylvania and New Jersey



Otter (River)

Background Information

The river otter is a water mammal belonging to the weasel family. As a result of trapping, hunting, and water pollution, the river otter was almost wiped out in Pennsylvania by 1900. Its fur was a very popular product.

By 1952, otters became protected by state law. By 1996, river otters were being released into Pine Creek (north central Pennsylvania), Loyalsock Creek (Sullivan and Lycoming counties), Youghiogheny River in Ohiopyle State Park, and Tionesta Creek in Allegheny National Forest. They are an endangered animal and are still protected by state law.

Physical Features

A full grown otter is a furry mammal weighing between 10 to 20 pounds. They are 30 to 40 inches (about 3 feet) in length. This does not include their tail which is about one foot long. Females are a little smaller.

Life Cycle

River otters mature at age 2. They mate between January and May. Two or three babies, called pups, are born about 2 months later. The pups are blind, toothless, and tiny, weighing about 5 ounces. An otter lives 10 to 20 years.


River otters make dens on the edges of lakes, rivers, creeks, or streams. Dens can be made under tree roots or rock piles. They can set up homes where beavers, woodchucks, and muskrats no longer live. Dens usually have an underwater entrance and a living area above the water level. They need clean water that supports fish and other marine (water) life.


Most of their food supply is made up of crayfish, minnows, and suckers (a type of fish). They are considered to be carnivores.


  © Dr. Randall Pellow, 2005