North American River Otter

Eric Orr
Photo courtesy NC Wildlife Resources Commission

Long ago, the North American River Otter thrived almost everywhere in North America. It was one of the most widely distributed mammals in the region. Now, due to unregulated trapping, pollution, and habitat destruction, the river otter occupies a fraction of its original range.

TRAITS AND HABITS

The river otter belongs to the Mustelidae family, along with weasels, minks, and badgers. They have long, thin bodies, short legs, and short snouts. The tail of an otter is long and thick and tapers to a point. An adult normally weighs from 12 to 23 pounds and can measure three to four feet long. They have small eyes and ears that lie flat against their heads. Their webbed feet and oily waterproof fur make them well suited for an aquatic environment. Like cats, otters have whiskers to help them navigate and locate prey in dark and murky water. Though they are mostly nocturnal, otters are sometimes active early and late in the day. They are secretive animals and to see one is a rare treat.

Most everyone familiar with river otters associates them with playfulness. They can sometimes be seen amusing themselves by sliding down mud and snow banks plunging into the water below. Some biologists believe, however, that the play is restricted to the young pups, and the adults are simply taking advantage of a quick mode of transportation.

At home in the water, otters can float on their backs, tread water, and swim either forward or backward. They are fast and nimble swimmers, capable of evading most predators. When otters submerge themselves their eyes are shielded with a clear eyelid called a nictitating membrane. This special trait allows the otter to see clearly underwater, while the eyes are protected. They swim by kicking their webbed rear feet and moving their bodies in a snakelike motion. Otters can stay underwater for up to four minutes and several hundred yards. Their speed and agility helps them catch fish and other small aquatic creatures. Although they are often mistakenly blamed for depleting trout populations, the otter’s diet consists mainly of small non-game fish. They can actually enhance trout habitat by feeding on species that would otherwise compete with trout. Otters prefer to feed mostly on slow swimming fish. Daces, suckers, perch, chubs, catfish, carp, and redhorses are a major part their diet. They also eat crayfish, insects, small mammals, birds, and some plants.

HABITAT

River otters are well adapted to a number of habitats. The main requirement is water, whether it be a mountain lake, a woodland river, or a small pond. They prefer clean, slow moving water with lots of fish. Proper cover is also essential to otters. Their habitat must include some kind of shelter. This could be in the form of a hollow log or tree trunk, a rock pile, a log jam, or the den of another animal. They’ve also been known to inhabit old boathouses and duck blinds. Streams and rivers seem to be more favorable, as they tend to have more cover and less human disturbance than lakes and ponds.

LIFE CYCLE

In early spring a soon to be mama otter starts to look for a den for her babies. She leaves the creek or river habitat to find an out of the way haunt by a complacent pond. She won’t dig her own den, but relies on another animal, like a beaver, to provide her with a home to raise her offspring. Once she’s settled in she’ll give birth to several tiny pups. There are any number from one to six of them, but a normal litter size is two to four. Each baby weighs about five ounces. They are helpless at birth, much like human babies. Their eyes are closed and they’re covered with a light coat of fur. After three or four weeks they open their eyes , and they begin to play soon after. The little otter pups are introduced to water by the time they’re seven weeks old, and they may leave the den by eight to ten weeks of age. They are weaned by ten weeks. The young otters are finally capable of fending for themselves when fall rolls around, but they usually stay with their families, which sometimes include the father, until the following spring. Then, right before the next litter arrives, the otter yearlings venture out in search of their own home ranges.

Breeding season comes right after the females give birth. It usually lasts about three months. As soon as they are bred, female otters go through a process known as delayed implantation. Instead of going into gestation right away, the embryos remain dormant in the mother’s uterus for about nine months. The actual period of gestation lasts about two months.

LIVING WITH OTTERS

Although otters are relatively safe in the water, they are much more vulnerable on land. Among their predators are bobcats, coyotes, foxes, dogs, wolves, and alligators. Young otters are the most susceptible to predation. None of their predators significantly impact their numbers, though. None except for humans. Traditionally, otters were trapped by Indians for clothing and adornments. Then white settlers began trapping and exporting them in the 1500’s. By the early 1900’s, they had been eliminated from a large portion of their original range, and by the 1980’s, river otters were rare in 13 states and extinct in 11. Several reintroduction programs were initiated and populations bounced back to some extent.

The river otter population of western North Carolina had been extirpated by the 1930’s. In 1992, the NC Wildlife Resources Commission trapped 49 river otters from eastern North Carolina and released them along the French Broad, Catawba, and other major rivers. The otters spread out and established themselves in their new homes. They are reportedly doing well. After the project proved successful, 37 more otters were released in the Great Smoky Mountains National Park, some of which have moved into North Carolina. Other states have tried similar programs, and now river otters are reported to be scarce or extinct in only 15 states. But it’s important to keep in mind that regional populations, like western North Carolina, may be low or nonexistent, while the entire state of North Carolina shows a healthy number.

20,000 to 30,000 otters are trapped each year for their pelts, and it’s still legal to trap them in 38 states. In the Chattooga River watershed, otters can only be trapped in Georgia and South Carolina. According to Jay Butfiloski of South Carolina Department of Natural Resources, the otter harvest is usually low in Oconee County. From 1995 through 2002, only 17 were reported, most of which were taken in recent years. Butfiloski attributes the increase to rising pelt prices, but he feels like more otters are taken through depredation permits. (Depredation permits are issued to landowners to reduce damage caused by animals such as beavers.) Though trapping is controlled by season, there is no limit on how many animals can be taken. The DNR imposes tighter restrictions when populations are reported to be low by trappers.

Some biologists say changes in otter numbers can be linked to beaver activity. Not only does beaver trapping directly affect otter populations, but actual changes in beaver occurrence and beaver habitat has a significant impact. In some areas otters may be somewhat dependent upon habitat created by beavers.

Habitat destruction is a serious threat to otters. The major culprits are recreational development of waterways, reduction of wetlands and riparian areas for farmland and new homes, and compromised water quality from increased runoff. In mountainous areas, roads and railroads contribute to a significant number of otter deaths, as they are often built next to streams and other waterways. Pollution also destroys otter habitat. Otters are extremely intolerant of chemical contamination. When land is cleared for farming, it not only increases the sediment levels in waterways, but it also introduces pesticides and herbicides. Past studies have indicated the presence of mercury and DDT, both common in pesticides, in the tissue of otters.

Wetlands and riparian areas are seemingly losing more legal protection every day, and with it, river otters lose protection. There is no way to stop development, but it can be controlled. The best way to ensure the survival of our otters is to vote for clean water and support sustainable agriculture and development.