Local otters make recent tracking trip a family affair

Posted: Friday, January 01, 2010

Just before Christmas, I returned from a sojourn in Chile. I left on one of the longest days of their year and returned to one of Juneau's shortest days. To help myself get back into winter mode and shake off the staleness of airplanes and airports, I went animal tracking in the fresh snow.

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Photo By Bob Armstrong
Photo By Bob Armstrong

Critters had been very active in the area between the Moraine Ecology trail and Mendenhall Lake. Snowshoe hare tracks were very common; lots of prey for a wolf, but our resident black wolf reportedly has not been seen for at least a couple months. A weasel had leaped across a rivulet and spent some time in front of somebody's small burrow. Mice or voles (hard to say which) had moved back and forth in the bushes along the trail, sometimes walking, sometimes running and occasionally making long jumps. One squirrel had ventured from the alders to the spruces. But bird tracks were conspicuously absent.

Cold temperatures had produced secure ice cover on the ponds, which made our passage far easier than it had been earlier in the season. This area contains extensive swamps, whose variable water depths had made walking a chore. We used the ice to gain access to corners of the swamps and ponds previously unexplored.

And we weren't the only ones using the ice. River otters recently had made a well-trampled path from one beaver pond, across the swamps, over some moraines and into a jungle of lace alder branches, unfortunately too thick for us to penetrate. This trail could have been made by a family group or a female and her pups.

There was no open water in the beaver ponds, except for some shallow, muddy seeps that allowed no access to deeper water for hunting fish. These otters kept moving, apparently, making short side excursions, but mainly trekking from one place to another. Otters may travel several miles in search of food, especially in winter when ice closes off many ponds. It would have been fun to follow their trail - in both directions - to learn the whence and whither of their travels. I later learned that a family of otters was seen on the Mendenhall River that same day.

Otters are often closely associated with beavers. They frequently use old beaver lodges and burrows for dens. Beaver ponds commonly harbor fish, which are a main component of otter diets. The dependence of otters on beavers, especially in winter, is so close that Canadian researchers have even suggested that the northern geographic limit of river otters may be set by the northern limit of beavers and trees.

Otters mate in spring, but development is delayed because the embryo is not implanted in the uterus until several months later. The young, usually two or three but occasionally more, are born the following late winter or spring and stay in the den for about two months. After they emerge, they have to learn to swim and dive and to find and catch prey. Developing all the needed skills takes some time, and they usually stay with their mother for about a year.

Officially, these are river otters, but locals sometimes call them land otters, perhaps to distinguish them from sea otters. Nevertheless, river otters are often seen in ocean waters near the shore, diving for food, or humping over the rocks near the tideline. Years ago, I used a float-house in a bay on Chichagof Island. A family of otters regularly used the floats under my bunkroom as a dining hall. Otters are noisy eaters; their grunts and snarls and the crunching up of prey provided good entertainment.

• Mary F. Willson is a retired professor of ecology.

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