Nature in the City:  |
Two
river otters spent a day in the lower pond at the University of Idaho
Arboretum this winter. |
by Sarah Walker, from the March 2006 Newsletter
One day this winter, much to everyone’s surprise, three river otters showed up in the lower pond at the UI Arboretum. No one had seen an otter there before.
Arboretum Manager Paul Warnick was one of the lucky few who got to watch them all day, swimming on their backs, sliding on the banks, and feasting on bass and bluegill. “They caught three of them in 15 minutes,” he said, “they were fun to watch.” Richard Williams saw them too, during his daily walk. They stayed at the far end of the pond, gradually got closer, then “frolicked around on the surface. They were a delight to watch. There was no sign of them when I went back the next day.”
These otters were likely a mother with her young from last year.
Otters’ high metabolism keeps them on the move in search of fish, crayfish, frogs or turtles, and they will investigate the smallest of creeks and drainage ditches leading to ponds. They have been known to range 30-40 miles along a waterway in their search for food. The Arboretum pond, stocked with fish, proved a bonanza for them. A plentiful food source, and the absence of danger (there are no dogs in the Arboretum, for instance), can make otters surprisingly tolerant of people, who take great interest in them.
North American river otters are large members of the mustelid family (skunks, mink, weasels) that weigh up to 30 lbs. Like other mustelids, they can emit a stinky substance for “scent marking,” and they are fierce about protecting their young. Otters are carnivores, with large teeth.
Unlike most mustelids, otters tend to be social and play together. They are well adapted for life in the water and are strong swimmers, with webbed feet, streamlined muscular bodies, and powerful, tapered tails that measure nearly a third of their four-foot body length. Their soft dense underfur and stiff guard hairs shed water and insulate them. Their stiff whiskers help them sense prey in dim light underwater, even in the darkness beneath winter ice and snow. They can swim 5 mph or more and stay underwater for five minutes.
On land, otters can reach 15 mph by alternately “bounding” and sliding on their bellies over slippery mud or snow.
In March or April, otters have two-three pups in a “natal den” inside an old beaver lodge. The pups weigh only 4-6 oz. and their eyes won’t open for a month. At six weeks, they’ll make their first trip outside the den for swimming and hunting lessons, and spend their first year with their mother.
Playing is thought to be a way for young otters to practice hunting techniques and form social bonds. But for adult otters, finding food and caring for young come before playing. Biologist Wayne Melquist, who has studied otters in Idaho, says “in captivity, where all life requirements are provided, play behavior by all age groups is much more prevalent, perpetuating the belief that otters must spend most of their time playing and sliding down muddy stream banks.”
Otters’ silky fur is highly valued, and was once their downfall. Otters originally lived along clean waterways throughout North America, but were trapped out of many parts of their range. Today, reintroduction programs and protection efforts have restored otters to all states except New Mexico.
Around Moscow, we might see other aquatic mammals in our creeks and ponds. Mink are smaller than otters, their feet are not webbed, and their tails don’t taper. Beavers are stouter and have wide, flat, scaly tails.
Sea otters are much larger, up to 80 lbs. and 6 feet long, and live primarily at sea in floating beds of kelp. River otters inhabit coastal areas, too, and in this food-rich marine environment they can be larger than inland otters. Both river otters and sea otters might overlap when sea otters come to land to give birth to their young.
Otters are rare visitors to Moscow. By now, this winter’s threesome could be miles away, a mother with her new litter tucked into a secluded den, the yearlings on their own searching for new territory and foraging miles every day in search of a meal.
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