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You can see the Zoo’s North American river otters in the Otter River exhibit near Penguin Island. Otter River was built in 1994 and features a cascading waterfall, two pools and naturalistic climbing logs.
River otters are medium-sized carnivore weighing from 11-30 pounds. Like other members of the weasel family, they have a long, flexible body and short legs. Their fur is short, dense and water resistant; making them well-suited to cold weather conditions. Both males and females are brownish-black but coloration varies widely based on location. Their underside is typically a creamy color but can range from pale brown to grey. Males are slightly larger and heavier than females.
The muscular tail and broad webbed feet make the otter an excellent swimmer and diver, able to remain under water for six to eight minutes. The otter can close its nostrils and ears under water, and uses the sensitive whiskers around its snout to help locate prey.
Lifespan is 13 years in the wild, and up to 25 years in captivity.
The North American river otter lives in Alaska, Canada and throughout the United States, except the dry Southwest. They are found along streams, lake borders, estuaries, and even seaside coves. Otters live in dens they dig on the banks of waterways, building long tunnels to create underwater entrances. In California, river otters can be found in the delta region of the Sacramento and San Joaquin rivers and Northern California rivers such as the Eel, Smith, Klamath and Russian.
Despite their charming appearance, otters are aggressive hunters but also opportunistic, eating whatever is available. The river otter dines on crayfish, frogs, fish, turtles, eggs, small rodents and occasional water birds. At the Zoo, they are fed a diet of fish, meat, vegetables, and eggs.
Social structure can vary depending on the location. In some areas otters are solitary, with males forming a dominance hierarchy where highest-ranking animals occupy the favorable ranges. In other areas otters will live in small family groups that hunt, travel and den together.
Territories are not defended and may overlap. Otters use scent marking to communicate information concerning sex, receptivity, and time elapsed between visits. Adult otters have a variety of calls, including whistles, hissing yelps, deep nasal growls, and a piercing scream.
Breeding occurs once a year usually between December and April. Up to five young are born after a gestation period of about 60 days. Implantation can be delayed, however, to ensure that births occur at the most favorable time. Youngsters emerge from the den and begin to swim at two months of age and reach independence at around one year.
North American river otters are listed as least concern by the IUCN although they have become rare in many parts of their range. Otters were once hunted excessively for their highly prized fur, so much so that populations disappeared from several states. Through regulations on hunting and trapping, as well as re-introduction initiatives, otter numbers are stable throughout most of their range. This species is still threatened by habitat loss, disease, pollution, and pesticide drainage into river systems.