Otters of Colorado
June 17, 2014
EAGLE COUNTY — The North American river otter (Lontra canadensis) is the only otter that lives inland on the continent north of Mexico. There is also a marine otter, often called a sea otter (Enhydra lutris). It is native to the coasts of the northern and eastern North Pacific Ocean.
River otters are members of the weasel family. They are very playful to watch, but perhaps are not as playful as many imagine. They tend to bound around and will slide down muddy or snowy slopes. Their favorite food is fish, but they also consume amphibians, crayfish and turtles. They may kill and eat birds, mammals, young beavers and muskrats. Just about any animal that lives in the water is food for otters.
Otters do not hibernate. They are active all year long. Their tracks in the snow are often created by a combination of bounding and sliding. They are well adapted for the water. Long bodies, strong tails and webbed feet allow them to move through the water with ease. They can hold their breath for up to eight minutes underwater.
OTTERS HUNTED FOR THEIR PELTS
The pelt of otters, which is gray and white or brown and black, is thick and waterproof. That caused their demise in many parts of North America. The French fur trade in the 1700s and 1800s eliminated hundreds of thousands of otters, many going to Russia. When felt hats became more popular than fur hats the market for otter and other furs began to decline.
The river otter life span in the wild is eight to nine years They are larger than some people expect with a body length 20 to 32 inches and a tail at 11 to 20 inches. They can weigh from 10 to 30 pounds. Their ears are small and they have a broad muzzle. This makes them distinct from beaver and muskrat when they are swimming. They mate in late winter, and there is a delayed implantation. Two to six pups are born early spring to mid-summer.
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Otters are often found where there are beaver and beaver lodges. They often use the old lodges and bank burrows as dens. A beaver dam in an area creates pools where fish can be found an increases the chance of observing an otter. An otter den typically has a number of tunnels and openings
Fossil records of river otters go back 365,000 to 1.4 million years in Colorado. Historically they have lived throughout the United States.
The population declined in Colorado in the late 1800s and early 1900s. Forty years ago the population may have been zero. Today, some estimates put the number at over 100,000 in North America. The current number of otters in Colorado is somewhat unknown. This is because the river otter is among the hardest mammals to census. Surveys rarely see river otters, but scat, dens and tracks provide a lot of evidence of their presence in Colorado.
OTTERS RETURN TO COLORADO
They were listed on the Colorado state endangered species list in 1975 following an early 1970 survey to determine if there were any populations of otters in Colorado. At that time, none were found. In 1976, a plan was proposed to restore river otters to the Colorado River in Rocky Mountain National Park. Because the site was protected by the National Park Service it was ideal for an introduction. Forty-one otters were obtained from Minnesota, Wisconsin, Oregon and Washington and released into the Colorado between 1978 and 1984. Radio transmitters were placed in a number of these otters and through the telemetry obtained, scientists were able to monitor the movements of the animals. Otters were also introduce into the Gunnison, the Piedra, and the Dolores rivers.
I was working as a National Park supervisory ranger naturalist in Rocky Mountain National Park when the otter were release into the upper Colorado River. I observed them a number of times. When I observed and photographed the otter shown in this story I wondered if they were the descendants of those otter I observed in the late '70s and early '80s.
Because of their population and habitat, the chances of seeing an otter in the wild are not good. Rafters and fisherman probably have the best chance of enjoying a sighting. Habitat destruction and degraded water quality due to pollution on Colorado's rivers is a threat.
Rick Spitzer is the author of Colorado Mountain Passes, published by Westcliffe Publishers and available at the Bookworm, Amazon, and many stores across the state. The book provides photos and text about the history, lore, wildlife, and scenery around the passes of Colorado.