Wolverine and River Otter

Meet two interesting species in the weasel (Mustelidae) family, the wolverine and river otter. Back to animal directory.

wolverine

LIFE SPAN: Up to 13 years in the wild, 19 years under human managed care.

RANGE: Wolverines have low densities in Alaska with a circumpolar range in the Northern Hemisphere. 

SIZE: Males are 30-40% heavier than females and can weigh up to 40 pounds. Females are typically between 13-26 pounds.

PHYSICAL FEATURES: Wolverines are the largest terrestrial member of the weasel family, Mustelidae. They have long, thick fur that is normally dark brown to black, a light-colored stripe along each side of their body and a light patch of fur on the neck and chest. They have short legs and ears, a flat head, a thick body, semi-retractable claws.

FOOD: Wolverines eat anything they can find or kill. They are opportunistic and adapted for scavenging. They have powerful jaws and neck muscles for breaking bone and frozen flesh. They survive extended periods of time on little food and their diet changes with season and food availability. They often eat voles, hares and birds. In some rare cases, they kill larger game such as moose, Dall sheep or caribou. In winter, wolverines eat carrion of moose and caribou left from other predators. In spring, they sometimes kill young Dall sheep.

BEHAVIOR: Wolverines are usually alone outside of breeding season. They are active any time of day and cover up to 40 miles per day in search of food. They avoid confrontation with large predators and will defend food resources and territories only against other wolverines and smaller predators. They prefer high elevations in summer and low elevations in winter due to the change in food availability. 

CONSERVATION: Wolverines are protected by preserving large expanses of wilderness and preventing overharvest by humans. Key wolverine habitat is protected by state and federal programs, however humans are expanding their recreational activities into more remote areas and this may cause issues for this secretive species, especially near denning sites.

North american river otter

LIFE SPAN: Up to 10 in the wild, mid-20’s under human managed care.

RANGE: River otters are found throughout Alaska except in the Aleutian Islands, off-shore islands of the Bering Sea and areas adjacent to the Arctic coast east of Point Lay. As their name indicates, they are North American river otters and they also range down through Canada and the Lower 48 states (north of Mexico).

SIZE: Males are much larger than females, at least 25% larger.  Adults weigh 15-35 pounds and are 40-60 inches long.

PHYSICAL FEATURES: River otters have long bodies with short feet. Their hind feet are webbed and they have a long, thick tail that is well-muscled to aid in swimming. 

FOOD: Rivers otters (sometimes called land otters) hunt on land, as well as in fresh and salt water. They eat a variety of foods that include snails, mussels, clams, sea urchins, insects, crabs, shrimp, octopus, frogs and a variety of fish. 

BEHAVIOR: Otters have “delayed implantation”, a period of arrested embryonic growth. If food is scarce or body condition poor, the fertilized egg will be expelled from the female's body.  This accounts for variations in their length of gestation (up to 6 months variation). Otters in Alaska breed in May and their young are born between January and June. Observers of river otters, whether in the wild or as visitors in a zoo, will notice their playful nature. River otters of all ages engage in play with each other, with objects and with their environment (sliding down muddy hills or snow). They are often seen wrestling and sleeping in a pile with each other at the zoo.

CONSERVATION: River otters have stable populations across their range in Alaska. Their only real predators are humans. River otters sometimes become trapped in fishing nets or crab pots. The loss of riparian (water's edge) forest habitat is a main threat to this species, as is water pollution. Contaminants in water impact their aquatic prey base and cause toxins to accumulate in their bodies since they are at the top of their food chain.