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The North American River Otter
By Toby Trigger

Posted: November 2, 2014

One of Montana’s most fascinating semi-aquatic mammals – What do you know about the River Otter?

Have you ever been canoeing and had three or more long sleek critters swimming close and dodging under your boat?  Or maybe you were fishing along your favorite stretch of river and saw a group of playful animals sliding into the water ahead of you or loudly chewing on a freshly caught fish.  Most likely what you saw was a river otter.

Red Rock Lakes NWR 101010 017

River Otters followed the authors boat for a mile on Red Rocks National Wildlife Refuge near Lima, Montana.

River otters average about 35 inches in length and can weigh up to 30 pounds.  Their fur is very dense and appears almost black when wet.  Very adept at swimming under water otters have muscles that will close off their ears and nose while submerged.


Otters were trapped by fur trappers who aided biologists in the successful reintroduction of the species in many states over the past two decades including Montana.  Today, otter trapping opportunities are expanding across western Montana and into the Missouri River drainages.

biologists with river Otters

Biologists and trappers successfully worked together to capture and release river otters across much of the United states. (photo credit:


River otters eat mainly fish, frogs, clams and crayfish and will eat muskrats as well.  Otters travel continuously following streams, rivers and around lakes.

otter eating fish

River otters rely on healthy river and stream systems for survival. Photo Credit (

Otters will often make “toilets” where large volumes of fish-scales and scat or found in a pile around root systems or rocks.  When the otters return on their travel routes they will use these same toilets over  and again.

otter toilet

Otter toilets like this can be found all around western Montana thanks to trappers and the MTFWP’s excellent otter conservation management. (photo credit:

Have you ever had an otter encounter or found a toilet?  Let us Know!


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