SUNY ESF
Short-tailed Shrew

(Blarina brevicauda Say)

From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp

Order: Insectivora
Family: Soricidae

Range and Habitat

The range of this abundant and widespread species includes the southern half of eastern Canada, and the eastern half of the U.S. Mixed and deciduous hardwood forest with thick, damp leaf mold harbor the greatest numbers of short-tailed shrews in the Adirondacks, but all terrestrial communities, e.g., coniferous forest, drier parts of swamps and bogs, marshes, and grassy openings, to an elevation of at least 1311 m (4300 ft) may have this small mammal as a resident.

As a general appearance indicates, the short-tailed shrew is more fossorial than other shrews, tunneling extensively, and to depths of 50 cm (20 in). Within the interwoven maze of tunnels that permeate the home range, it gathers and shreds leaves and other plants materials to build resting and breeding nests 15-20 cm, (6 – 8 in) in diameter. These nests may be 30.5 cm (12 in) beneath the surface of the soil or under a rock or log.

Food and Feeding Behavior: The neurotoxic saliva of the short-tailed shrew is a unique adaptation among North American mammals. Its poisonous bite is a result of secretions of the submaxillary glands which contain enough toxin to kill approximately 200 mice. Saliva flows into wounds via the channel formed from the union of the lower pair of incisors. While the function of the toxin is not clearly known, it probably serves to immobilize small animals and stun larger ones.

A major part of the diet of the short-tailed shrew consists of small invertebrates, especially earthworms and large insects, that a shrew catches and immediately severs with its sharp teeth, and then swallows. However, the diet also include vertebrates much larger than itself such as mice, young hares and rabbits, nestling birds, salamanders, and snakes. Plant foods, e.g., beechnuts and other seeds, berries, and fungi, form a small but important part of the winter diet. Satiated shrews cache excess prey, particularly snails and earthworms, after biting and paralyzing them.

Activity and Movement

The cold temperatures and deep snows of an Adirondack winter do not suppress the activity of the short-tailed shrew. It tunnels through the snow and forages on the surface, usually at night, or burrows just beneath the surface, pushing up the crust to create miniature molelike ridges approximately 19 m (0.75 in) wide. Some winter activity takes place on or in the soil, under the insulating snow cover. Short-tailed shrews push their way through the leaf mold by day or move about on top of the ground at night during the warmer seasons. They use their forefeet and snout to loosen compacted soil when digging their permanent subterranean burrows that are about 4-5 cm (1.75 in) wide. Short-tailed shrews exhibit the typical pattern of shrew locomotion. They run, stop suddenly, and walk with quick jerky steps. They constantly thrust their ever- twitching snouts under leaves or twigs, and then up into the air, turning their heads from one side to the other. Any noise or sudden movement causes them to vanish by running into a burrow or by skipping beneath the soil or snow. This species emits ultrasonic sounds for echolocation, an obvious advantage for its semi-fossorial lifestyle.

Reproduction

A receptive female mates 20 or more times, during a 24-hour period. These multiple copulations, which average 4-5 minutes in duration, trigger ovulation. Females produce 1- 3 litters from late winter until early autumn. The gestation period is 21-22 days. The newborn young are pink, hairless, 22 mm (0.9 in) in length, and weigh slightly more than 1 g (0.04 oz). They develop fur by day 14, and their eyes open at day 18-20. At this time the young shrews begin to leave the nest. They are weaned and independent at 25-30 days. Females may breed when 30-60 days old; males somewhat later, but usually not until the following spring. The maximum life span of this species is three years, although few individuals live beyond 18 months.

Predators

Hawks, owls, snakes, and larger mammals prey upon short-tailed shrews. Mammalian predators may sometimes kill but then do not eat this species because of the “sour” odor produced by skin glands. Short-tailed shrews entering water, or as more likely, swept by flooding, may be eaten by fish, e.g., the stomach of a 71 cm (28 in) northern pike taken from Rich Lake, Essex Co., October 4, 1986, contained one adult short-tailed shrew.

Social Behavior

• Social System -  The short-tailed shrew is promiscuous and solitary. Individuals have home ranges of 0.1-1.8 ha (0.25-4.5 ac) which overlap. Densities of 5-25 shrews per ha (2-10 shrews per ac) are typical for this species but may reach 120-200 per ha (48-80 per ac). Local populations fluctuate appreciably from one year to the next.
• Communication -  Chemical and vocal signals play a major role in regulating social encounters. Products from the lateral skin glands of males and non-breeding females elicit avoidance or antagonistic behavior. Continuous “clicks”, e.g., given by males in courtship bouts, or by displace young, function as contact calls. Repetitive “puts” and “twitters” space individuals. The “buzz” and “chirp” accompany antagonistic encounters. A short-tailed shrew I approached on a winter night adopted a “tripedal threat” and gave a loud, sharp, ascending “twittering-chirp” audible to at least 3 mm (10 ft).

Additional References 

Blus, L.J. 1971. Reproductive and survival of short-tailed shrews (Blarina brevicauda) in capitivity. Laboratory of Animal Science, 21:884-891.

Buckner, C.H. 1964. Metabolism, food capacity, and feeding behavior in four species of shrews. Canadian Journal of Zoology, 42:259-279.

Olsen, R.W. 1969. Agonistic behavior of the short-tailed shrews, (Blarina brevicauda). Journal of Mammalogy, 50:494-500.

Tomasi, T.E. 1978. Function of venom in the short-tailed shrews, (Blarinabrevicauda). Journal of Mammalogy, 59:852-854.