The Wilderness Classroom

Otters

River otters are the most playful animals in the Border Country. Otters are often found frolicing in the water alone or in groups. They enjoy jumping and playing in river currents. In the winter they slide on their bellies on the ice to make travel much faster. Infact, when they get up enough speed they can run and slide a distance of 27 feet!

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What do otters look like?
Otters are part of the same family of animals as weasels, badgers, and pine martens known as mustelids. They have streamlined bodies that allow them to be excellent swimmers. They weigh between 11-30 pounds with the males weighing more than the females. Most of the otters in the Border Country do not exceed 20 pounds and 4 feet in length. Otters are dark brown with paler brown bellies. They have small eyes and ears and long tails. Their ears and noses have adapted to keep water out with valves that close when they are underwater. Otters have very noticeable whiskers that are long and white. Not only are otters the most playful animals, they are also very cute!

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Where do otters live?
River otters are found in lakes, streams, rivers, and ponds in forested areas. They also spend a lot of time on land.
River otters are found all along the east coast of the US, northern parts of the Midwest, in the Pacific Northwest, and most of Canada.
They live in dens along the banks of rivers and lakes. Sometimes otters will dig their own dens or else use hollow logs, overhanging roots or other empty animal burrows. The dens have underwater and aboveground entrances. During the winter, otters can breathe in the space between the bottom of the ice and the lowering water.

Did you know that otters can dive deeper than 50 feet underwater?
Otters can dive as far down as 55 feet! They can also swim a 1/4 mile with only 1 breath and can stay underwater for 2 minutes.

What do otters like to eat?
Otters eat lots of fish but also mice and small invertebrates such as crayfish. They primarily eat slow moving fish like suckers and catfish. Otters use their whiskers to locate crayfish, turtles, and fish along the bottom of the water. Sometimes otters work together as a team and scare the fish into small alcoves in the water where they can be caught easily. Otters even eat muskrats and beavers!

What are some signs of otter activity?
In winter, otters will make holes in the snow and also snowslide trails that are about 1 foot wide. In the summer, they leave slide marks along riverbanks. They often litter the trails with crayfish droppings.
Otter tracks are about 3 inches wide. Their 5 toes spread out like a fan. Usually only the heel pad and claws can be seen in the tracks.

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When are the cubs born?
Otters have litters of between 1 and 6 cubs. Two is the most common number of cubs in a litter. The cubs are born in March or April. The mother otter will find a den suitable for her young just before they are born. The cubs nurse until they are about 4 months old. They also learn how to swim and hunt by watching their parents. When the cubs are very young the mothers send the fathers out of the den. When the cubs are half grown, the fathers are welcome back into the den to help care for the young.

Are river otters sociable with each other?
River otters are often found playing together in the water. Males are sociable most of the time except for during the breeding season. During the breeding season, they will sometimes get in fights with other males.

Next time you are near fresh water lakes or rivers keep a look out for these cute, playful animals!

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What are some of the problems that otters face?
Otters are at the top of the food chain and do not have many natural predators. In the past, humans hunted otters for their thick, warm fur. Trapping is not as common these days. The largest threats for otters today are pollution of lakes, ponds, and rivers and also humans moving in on their territory. When humans use pesticides on their crops, the rain washes these chemicals into the water and poisons the fish. The otters eat the fish and the poison can make it difficult for them to breed.

Sources
Banks, M. 1988. Discovering Otters. The Bookwright Press. New York.
Stensaas, M. 1993. Canoe Country Wildlife: A field guide to the North Woods and Boundary Waters. Pfeifer- Hamilton, Duluth, MN.
Whitaker, J.O. 1998. National Audobon Field Guide to North American Mammals. Alfred A. Knopf, Inc.