River otters feed primarily on fish and are found in streams, wetlands, lakes and reservoirs and along the coast throughout the United States and Canada. They are skilled hunters and are opportunistic, also preying on shellfish, crabs, frogs, insects and birds. When hunting, river otters have the ability to stay underwater for as long as eight minutes and can close their nostrils and ears to protect them.
River otters typically settle in areas where there is abundant water and food sources, as well as vegetation and structures such as rock piles. They live in groups that usually consist of adult females and pups, but groups of individual males have also been observed.
River otters are playful and intensely curious. They have been seen in “play behavior” sliding down muddy banks or snow drifts on their bellies into the water. They have also been observed swimming in circles to create small suction whirlpools that draw fish up from the river’s bottom.
River otters mate during the months of December to April and produce litters that consist of two to three pups. Females are only in estrus for one month during the year. The females have delayed implantation and carry fertilized eggs for about seven to 10 months before the eggs implant. Pregnancy lasts for approximately 302 to 351 days.
The pups are unable to swim until they develop a dense undercoat, usually when they about 2 months old. Young otters frequently climb onto their mothers’ backs when learning to swim.