Montana Field Guide

This house cat-sized animal is distinctly weasel-like in appearance. Has short legs, prominent ears, pointed face, and a well-furred tail constituting one-third of its total length. Stiff glossy guard hairs with dense silky under-fur. The soft, dense, yellowish-brown fur shades to dark brown on its bushy tail and legs. Pale buff to orange patch on throat and breast. Has ability to rotate hind limbs to enable descending trees headfirst. Total length: 21 to 26 inches. Weight: 1.5 to 2.75 pounds (Foresman 2012).

Recent genetic data indicate that there are two species of Marten within Montana with a zone of hybridization that still needs to be mapped to inform conservation status designations and management efforts; Pacific Marten (Martes caurina) has more of a southern distribution and American Marten (Martes americana) has more of a northern distribution in western Montana (Dawson and Cook 2012, Dawson et al. 2017).

Mink has white patch on chin. Fisher is larger, dark brown with grizzled head and back. Red Fox has white tip on tail.

Non-migratory.

Primarily a boreal animal preferring mature conifer or mixed wood forests. Severe forest disturbance can significantly reduce habitat value. Uses deadfall and snags as den sites. In Glacier National Park, most often located in mesic spruce and subalpine fir types. Stands averaged 35% canopy cover. Martens often traveled along forest cover/open area ecotones. Maternity dens in rock outcrops, tree cavities (O'Neill 1980, Burnett 1981).

Eats a variety of animal and plant materials associated with the mature forest. Is an opportunistic feeder that primarily feeds on a variety of small mammals. Meadow Voles and Red-backed Voles were staples in Glacier National Park. Also used Cricetidae, jumping mice, shrews, and ground squirrels. Use of birds, insects, and fruit variable by season. Will use snowshoe hares (O'Neill 1980).

Populations fluctuate in response to prey availability, juvenile dispersal, and mortality of adult females. Average home range for adult male = 2.9 sq km, female = 0.7 sq km, resident juveniles = 0.7 sq km (Burnett 1981).

Mates during summer with young born during April. Exhibits delayed implantation and an eight- to nine-month gestation. Average litter size is two to four. Breeds in July and August. Implantation occured February 22 and April 10. Parturition 25 to 28 days after implantation. Delayed implantation period of 8 months. Gestation of 9 months.

Prior to 1953, two extant species of Marten were recognized within North America, the American Marten (M. americana) and Pacific Marten (M. caurina). However, Wright (1953) analyzed morphometric differences between these species and concluded that these should be considered subspecies of M. americana, and a single species of marten was recognized until 2014. In 2014 the "Revised Checklist of North American Mammals North of Mexico, 2014" (Bradley et al. 2014) elevated the status of the Pacific Marten from subspecies of American Marten to species based on recent research on marten genetics (Dawson and Cook 2012). Within Montana hybridization between Pacific and American Martens has been documented (Wright 1953, Dawson and Cook 2012, Dawson et al. 2017), although the geographic region where hybridization occurs, or its impacts on fitness and other population parameters are currently unknown.