Otters
Otters are playful and intelligent mammals belonging to the family Mustelidae, with two primary species: river otters and sea otters. River otters, found in North America, can grow up to 127 centimeters long and weigh between five and fourteen kilograms. They possess dense, water-resistant fur that helps them thrive in aquatic environments, primarily feeding on fish and crustaceans. River otters are known for their curious nature and social behaviors, often playing and grooming themselves on various surfaces.
In contrast, sea otters inhabit the northern Pacific Ocean and are larger, weighing between twenty-seven and thirty-eight kilograms and reaching about 148 centimeters in length. They have a unique adaptation, relying on their dense fur for insulation rather than blubber. Sea otters are also notable for their tool use, often employing rocks to crack open shellfish while floating on their backs. Both species face threats from predators, habitat destruction, pollution, and overtrapping, highlighting the importance of conservation efforts to protect these fascinating creatures.
Otters
Otter Facts
Classification:
- Kingdom: Animalia
- Phylum: Chordata
- Class: Mammalia
- Order: Carnivora
- Family: Mustelidae
- Subfamily: Lutrinae
- Genus and species:Lontra canadensis (North American river otter),Lontra felina (marine otter),Lontra provocax (southern river otter), Lontra longicaudis (neotropical river otter);Lutra lutra (European otter),Lutra sumatrana (hairy-nosed otter),Hydrictis maculicollis (spotted-necked otter);Lutrogale perspicillata (smoothed-coated otter);Aonyx capensis (Cape clawless otter);Pteronura brasiliensis (giant otter);Amblonyx cinereus (oriental small-clawed otter);Enhyda lutris (sea otter)
- Geographical location: Every continent, except for Antarctica. Until the eighteenth century, North American river otters were found in all major water courses in the United States and Canada; presently, North American river otters are scattered in several river systems across the United States and Canada, and many river otters have been reintroduced into river systems where they once flourished. Sea otters are found along the Pacific Coast of North America. European otters are found all across Europe and in most of Asia and parts of North Africa. The spotted-necked otter and the Cape clawless otter are native to sub-Saharan Africa. The smoothed-coated otter and the hairy-nosed otter are native to Southeast Asia, although the hairy-nosed otter is exceedingly rare and was thought to be extinct during the 1990s. Neotropical otters live in Central and South America. Giant otters, southern river otters, and marine otters are found in South America, although they are considered threatened.
- Habitat: Exclusively aquatic, adaptable to many nonpolluted aquatic environments
- Gestational period: 288 to 375 days, with delayed implantation
- Life span: Ten years, with a maximum of twenty-three years
- Special anatomy: Webbed feet
Playful and proud, otters seem to have been born to have fun. At least, it appears that river otters are having fun, because of their playful antics with each other, as well as their facial and body expressions. By any measure, otters are extremely curious and intelligent mammals.
River Otters
Adult river otters reach a length of about 127 centimeters, including their tails, which are nearly one-third of that length. Adults weigh between five and fourteen kilograms. Females are slightly smaller than males.
River otters have a dense, short fur with great water resistance. Air is trapped beneath their dense furry coats and acts as insulation against the cold water, where these mostly aquatic mammals feed. Otters roll and rub themselves on sand, rocks, old logs, and even snow in their coat grooming activities. These carnivorous mammals mostly feed on fish. Crayfish also serve as diet items when abundant. Researchers have found that river otters feed directly on fish proportionally to their availability and inversely to the fish’s swimming ability.
Shelters that have been abandoned by other animals are frequently used by river otters, such as old beaver dens or riverbank excavations. On occasion, river otters use rock piles and log jams as dens. Some investigators have discovered nests along river and stream banks which river otters had constructed of aquatic vegetation.
Mating activity usually occurs in the water, although there are reports of mating on land. The breeding season is usually late winter to spring. Litter size is between one and six cubs. The newborn otters have full pelage, but their eyes are not open and they have no erupted teeth. Females wean their young at about three months of age.
Several predators, including bobcats, foxes, and alligators, have been observed hunting river otters. Humans also have made their impact on otter populations in at least three ways: habitat destruction, water pollution, and overtrapping.
Sea Otters
Sea otters are confined to the northern Pacific Ocean. Being the largest in the family Mustelidae, sea otters weigh between twenty-seven and thirty-eight kilograms and attain a length of about 148 centimeters. Unlike seals and whales, which have a fat layer (blubber) for insulation, sea otters rely on air trapped beneath their densely packed pelage. Some researchers have estimated the number of hairs in a sea otter’s coat to be 800 million.
Sea otters, just as their freshwater cousins, have delayed embryo implantation. Females usually produce one pup in a litter. The pup is unable to swim or dive until it is two to three weeks old.
Food preferences of sea otters include abalones, sea urchins, clams, and crabs. It is a common practice of sea otters to eat while floating on their backs. Furthermore, sea otters use rocks to open the shells of their diet items, making them a member of a small group of animal tool users.
Unlike other members of the Mustelidae, sea otters lack functioning anal scent glands. Also, unlike most carnivores, sea otter teeth are adapted to crushing their prey, rather than tearing.
Principal Terms
carnivore: an animal that feeds on other animals for its diet
delayed implantation: a process of delaying the implantation in the uterine wall of the fertilized egg
dorsal: the back portion of an animal
notochord: a dorsal, flexible, rodlike structure extending the length of a vertebrate’s body; serves as an axis for muscle attachment
pelage: a mammal’s fur coat
predator: an animal that preys on other animals for its food
Bibliography
Buchsbaum, Ralph, et al. The Audubon Society Encyclopedia of Animal Life. New York: Crown, 1982. Print.
Chanin, P. The Natural History of Otters. New York: Facts on File, 1985. Print.
Chapman, J. A., and G. A. Feldhamer, eds. Wild Mammals of North America. Baltimore: John Hopkins UP, 1982. Print.
Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. Mammalogy: Adaptation, Diversity, and Ecology. Boston: WCB/McGraw-Hill, 1999. Print.
Hall, E. Raymond. The Mammals of North America. 2 vols. 2nd ed. New York: Wiley, 1981. Print.
Kruuk, Hans. Otters: Ecology, Behaviour and Conservation. Oxford: Oxford UP, 2006. Print.
Yoxon, Paul, and Grace M. Yoxon. Otters of the World. Dunbeat: Whittles, 2015. Print.