Montana Field Guide

The Northern Short-tailed Shrew is realtively large and robust, with inconspicuous ears and minute eyes. The snout is pointed and somewhat proboscis-like but relatively shorter and thicker than in other shrews. The tail is relatively short (< 20% of total length), hairy, and faintly to distinctly bicolored. Dorsal pelage is slaty gray, darker in winter than summer (Jones et al. 1983, Van Zyll de Jong 1983, George et al. 1986). Large adult size and relatively short tail distinguishes this species of shrew from any other in Montana.

A relatively large and robust shrew (total length usually > 110 mm, occipito-premaxillary length usually > 21.5 mm) with a relatively short tail (20% of total length). Dental formula as in shrews of the genus Sorex, with 32 total teeth (including 5 unicuspids in each upper jaw).

The species is considered non-migratory, although information on movements is lacking for Montana.

Considered hypothetical in extreme northeastern Montana since at least 1968 (Hoffmann and Pattie 1968) until two were captured in August 2005 in Sheridan County in marshy, prairie pothole habitat about 1.35 miles (2.2 km) south of the Saskatchewan border. Farther east, within the main range of the species, Northern Short-tailed Shrews are most common in hardwood forests with deep leaf litter and in brushy sites adjacent to ponds and streams, less common in conifer forest and grassland. In Manitoba, this shrew is reported to be most common in grass-sedge marsh and willow-alder shrubs (Jones et al. 1983, Van Zyll de Jong 1983, George et al. 1986).

Food habits have not been studied in Montana. Elsewhere, the diet includes a variety of invertebrates, including insects (esp. Lepidoptera, Diptera and Coleoptera larvae), millipedes, annelids (earthworms), mollusks (snails and slugs) and terrestrial amphipods (sowbugs). Vertebrates are less important than invertebrates, but during winter may capture small mammals such as voles (Microtus spp.) and smaller shrews (Sorex spp.). Sometimes food is hoarded. Infrequently attacks much larger animals (e.g. gartersnakes). The saliva is poisonous (even to humans) and aids in capture of prey; may vocalize when feeding (Jones at al. 1983, Van Zyll de Jong 1983, George et al. 1986).

Little ecological information is available for the Northern Short-tailed Shrew in Montana. Elsewhere, the species is active throughout the year, both on the surface and in tunnel systems (its own and those of other small mammals). It is active day and night for short periods, but may be inactive up to 80% of the day, by drastically lowering its resting metabolic rate. Nests are built underground, and may be lined with vegetation or animal fur from voles. Two distinct age classes are evident in summer and autumn, representing adults born the previous year and young of the current breeding seasons. Densities can range from 1.6/ha to 121/ha, with home-ranges averaging about 2.5 ha. Winter mortality in some populatons may reach 90%. Raptorial birds and snakes appear to be the main predators of Northern Short-tailed Shrews, as they seem to be distasteful to most mammalian predators (Jones et al. 1983, Van Zyll de Jong 1983, George et al. 1986).

No information from Montana. Throughout the range, breeding may occur any month, usually during February to October but greatly reduced during summer. Gestation is 21-22 days, average litter sizes range from 4 to 10, weaning occurs by 25 days of age, adult size (but not weight) is reached by about 50 days, females are reproductively receptive when about 50 days of age, males at about the same age (65 days the earliest successful reproduction reported). Adults may live up to 33 months (Jones et al. 1983, George et al. 1986).

No management needs have been identified and no measures have been enacted to promote Northern Short-tailed Shrew conservation in Montana. Wetland drainage or alteration, and loss of riparian vegetation (e.g. aspen, birch, willow, cottonwood) in woody draws and around springs or seeps, has the potential to negatively impact local populations. Additional surveys for Northern Short-tailed Shrew can provide the basis for development of conservation protocols by determining its full distribution in Montana, the array of habitats in which it occurs, its relative abundance in different habitats, and, if properly designed, an idea of how different habitat disturbances affect this shrew at the margin of its global range.