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Nature Notes: River Otters

Ed Robinson
September 28, 2013

When I first saw the creature at a distance, swimming toward me in the ocean, I thought it might be a muskrat. As it came closer, it looked large enough to be a beaver. But when the animal rolled and dove, I knew it was an otter. It was a delight to watch her for a few minutes but then she was on her way.

Since we don’t have sea otters on the East coast, you might find it strange that a river otter would be swimming in the ocean. But these beautiful animals are at home around any body of water that offers a meal. Evolved to survive in a wide range of conditions, river otters have streamlined bodies with short legs, sharp claws and webbed paws. Their fur is luxurious, especially in winter when they add a dense under layer for insulation. An adult male (properly called a “meowter”) can reach 4 feet long and nearly 30 pounds, and is quite capable of defending himself with his powerful muscles and sharp teeth.

Otters are motion machines, spending several hours each day and night foraging for food. They have a high metabolic rate so they must feed regularly, up to 15% of their body weight per day in colder conditions. Fish makes up the bulk of their diet, but they are opportunistic feeders, taking frogs, crabs, shellfish, eggs, even small birds and mammals. To locate food, otters will travel up to 25 miles in family groups that include the mother and her young of the year (the group is called a “bevy”, a “lodge” or my favorite, a “romp”). But the day will also include mock fighting and sliding down stream banks for no apparent purpose other than having fun.

During breeding season, males have been known to range as far as 150 miles to keep an eye on their territories. Like others in the Mustelidae family (including weasels, mink, badgers and wolverines), otters have two scent glands adjacent to their anus and they use the musk from these scent glands to communicate with each other. If two males encounter each other with an estrus female nearby, there may be a vicious fight to win her.

The female (known as a “queen”) takes up lodging in anticipation of giving birth. Her den is well hidden, and may be in a hollow log, in an abandoned beaver house or under a boat house or log jam. This den is called a “holt” or a “couch.” After 2 months gestation, 2-4 pups are born. The pups feed on mother’s rich milk for 2 months and then begin to swim and are introduced to solid food. They are capable of feeding themselves within a few weeks and in the autumn, the offspring separate from their mothers to find new territories.

When Europeans first pushed into the new American wilderness, otters were actively hunted and trapped for their valuable pelts. With much less demand for fur products today, otters are not listed as an endangered or threatened species in North America. Like other secretive animals, we rarely see otters and they prefer to avoid human contact. It is wonderful to think that otters live in our hometown, but if you encounter one, give him a wide berth since they can be aggressive if cornered or threatened.

Maine is blessed with a healthy population of otters and if you spend enough time along streams and quiet ponds, you may be lucky enough to see one.

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