Northern River Otter

    Order Carnivora
    Family Mustelidae
     Lutra canadensis



Written by Stephanie Cruise

River Otter

Geographic Range


The river otter can be found in most of Canada with populations extending south into northern California and Utah. On the eastern edges of the United States, otters can be found from Maine all the way to Florida. They are also found in Newfoundland and in some parts of the Midwest, they are being reintroduced.

Physical Characteristics


An otter is dark brown on the dorsal side with a light gray ventral side. Its fur is waterproof and when wet it looks black. The otter has a long body which is broad. Its head is sort of flattened. The otter's throat is usually gray and they have very obvious long, whitish whiskers. The eyes and ears are small. The ears are not easily seen. The otter has a long thick tail which is very muscular and powerful. The tail tapers to a pointy end and has a length of 320-500 millimeters. The otter has feet which are fully webbed and measure 110-135 mm. The total body length of the otter is 900-1300 mm and they usually weigh in between 5-14 kg.

Natural History


Food Habits

The otter is a largely carnivorous mammal. It has a very diverse diet. It typically preys upon such fish as minnows, carp, suckers, darters, chubs, daces, catfich, blue-gills, and sticklebacks. However, they can catch faster fish such as trout, perch, and sunfish. Other things included in an otters diet are crayfish, clams, amphibians, and sanll animals which could include small birds, mice, etc. The otter usually forages for its prey at night. The prey are ambushed with a quick lunge or sometimes after long pursuits.

Reproduction

The mating season for otters begins in early spring. Female otters enter heat right after giving birth to a litter and mate sometime soon after. The gestation period is a very long 9-13 months due to a process of delayed implantation. There is a 9-11 month timespan of suspended development where the embryos remain dormant until about 2 months before the young otters are born. An average otter litter is between 2-3 babies but could reach 5 babies. The babies which are called kits are born totally covered with fur. However, they are blind, have no teeth and are totally helpless. The otter mother is known for being a fierce protector to its young. The young open their eyes after 5 weeks. Solid food can be eaten at the age of 9-10 weeks. Swimming is taught around 8 weeks of age and the young are totally weaned by the age of 12 weeks. Females are sexually mature by the age of 2 and will mate while males wait until the age of five. Otter will usually live to the age of 13 and can even reach the age of 20 in captivity.

Behavior

An otter can be seen at all times during the day if it is not disturbed by human presence. Otherwise they are nocturnal. The animal spends time both on land and in the water. In fact they are very well suited for aquatic life. An otter's ears and nostrils have valves to keep water out while swimming. It is also a very good swimmer. The otter can swim at speeds up to 7 miles per hour and can dive to depths of 18 meters. They can also stay under water for several minutes. On land, otters use many means to get around. Usualy they wander along slowly but they can also run. They are notorious for sliding on their bellies which they will do on ice, snow, mud or grassy vegetation. An otter uses a variety of sounds to comunicate. This includes whistling, chattering, chuckling, chirping, grunting, snorting, and growling.

Habitat

Otters usually live in wooded areas near rivers, ponds, and lakes. However,it is possible to find them far away from wter. The otter lives in a nest underground made of sticks, grass, reeds, and leaves which is connected to a pond or stream by means of an underwater entrance. These nest are usually made by other animals such as the beaver or the muskrat and the otter will come in and fix them to their liking. Other possible places for the otter to take refuge are hollow logs, beaver lodges, and among tree roots.

Economic Impacts

The otter has one main economic impact. They are often trapped for the use of their fur. Not only is their fur beautiful, but it is very thick and durable. Trapping for this reason has greatly depleted the numbers of otters in the United States and Canada.

Interesting Facts

Did you know that the otter used to be very abundant? In fact they used to populate most of Canada and the United States. However, trapping, human habitation and pollution have greatly depleted their numbers. Did you know that efforts have been made to return otters to places which they once inhabited? In New York, the New York River Otter Project, was put together to attempt to bring the otters back. Their goal was to raise $300,000 and relocate 270 otters from the Adirondacks and Catskills to New York. They have succesfully transferred 21 otters. Similar efforts have been made in the Midwest. Did you know that some otters can overcome pollution? In fact, in recent years, it has been found that some otters may be becoming tolerant to certain pollutants such as mercury and organochlorine compounds. This tolerance has caused populations to start a steady increase.

References


Duplaix, Nicole and Noel Simon. 1976.
World Guide to Mammals. Crown Publishers, Inc. ISBN: 0-517-529203.
Kurta, Allen. 1995.
Mammals of the Great Lakes Region. The University of Michigan Press. ISBN: 0-472-06497-5.
Money, Dennis J. 1996.
Welcome Back, Otter. New York State Conservationist 51(1):18-20.
Nation Audubon Society. 1996.
Field Guide to North American Mammals. Alfred A. Knopf, Inc. ISBN: 0-679-44631-1.




Any comments or suggestions? If so, please send them to Buzz Hoagland (bhoagland@wsc.mass.edu)

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