Montana Field Guide

Northern River Otter - Lontra canadensis

The adult northern river otter in Montana weighs around 20 pounds and measures close to 47 inches long. Its thick, powerful tail makes up nearly 20 inches of that length. Small eyes and ears, a broad, flattened head, long cylindrical form, and four webbed feet suit it for its semiaquatic life. In addition, its fur, dark brown on top, silvery or paler brown on the throat, chest, and underside, has special qualities. The long guard hairs remain pliable in very cold weather (Ulrich 1986), and the dense underfur traps air to insulate the otter in water. The otter can dive to 45 feet and stay underwater for some minutes (Zeveloff 1988). The otter is more nocturnal in summer and its eyes reflect a faint amber glow at night. Its short, muscular legs move surprisingly well on land, and is usually seen to travel in pairs (Foresman 2001). It has 36 teeth. The young are born fur-covered, but blind ( Burt and Grossenheider 1964); however, they are ready to fend for themselves at eight months of age (Zeveloff 1988).

Montana Range

Non-migratory.

High flow volume water, densely vegetated and undercut banks preferable, nonturbid water and presence of sloughs and side channels to serve as brood rearing habitat are also important in winter. Open-water stream channels used. (Zackheim 1982).

Mainly fish. Order of importance varies--sunfish, suckers, sculpin, trout, invertebrates, & frogs versus suckers, sculpines, whitefish, trout, & invertebrates. Food availability (determined by prey number & characteristics) determines level of use (Zackheim 1982, Greer 1955).

Otters frequently inadvertantly caught in beaver sets. Per- haps higher human-caused mortality than reported. Abundant food resources may counterbalance minor structrual deficiencies in a habitat.

Probably breeds every 2-3 years. Breeding dates not known for MT. Probably early Spring. Altricial young weaned in 91 days (Toweill and Tabor 1982).