SHREWS Utah State University Logan, Utah 84322-5210
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Robert H. Schmidt Assistant Professor Department of Fisheries and Wildlife SHREWS Utah State University Logan, Utah 84322-5210 Fig. 1. A masked shrew, Sorex cinereus Identification Damage Prevention and Fumigants The shrew is a small, mouse-sized Control Methods None are registered. mammal with an elongated snout, a Trapping dense fur of uniform color, small eyes, Exclusion and five clawed toes on each foot (Fig. Mouse trap (snap trap). Rodent-proof structures also exclude 1). Its skull, compared to that of shrews. Small box trap. rodents, is long, narrow, and lacks the zygomatic arch on the lateral side Cultural Methods Pit trap. characteristic of rodents. The teeth are Mowing may decrease preferred Shooting small, sharp, and commonly dark- tipped. Pigmentation on the tips of the habitat and food. Not practical. teeth is caused by deposition of iron in Repellents Other Methods the outer enamel. This deposition may None are registered. Cats may reduce densities around increase the teeth’s resistance to wear, Toxicants structures. Owls consume large an obvious advantage for permanent numbers of shrews. Mowed grass teeth that do not continue to grow in None are registered. around structures may increase response to wear. The house shrew predation. (Suncus murinus) lacks the pigmented teeth. Shrew feces are often corkscrew- shaped, and some shrews (for PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994 Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska - Lincoln United States Department of Agriculture Animal and Plant Health Inspection Service Animal Damage Control D-87 Great Plains Agricultural Council Wildlife Committee example, the desert shrew [Notiosorex Food Habits venom in their saliva that may help crawfordi]) use regular defecation them subdue small prey. stations. Albino shrews occur occa- Shrews are in the taxonomic order Some shrews are mostly nocturnal; sionally. Shrews are similar to mice Insectivora. As the name implies, others are active throughout the day except that mice have four toes on insects make up a large portion of the and night. They frequently use the tun- their front feet, larger eyes, bicolored typical shrew diet. Food habit studies nels made by voles and moles. During fur, and lack an elongated snout. have revealed that shrews eat beetles, periods of occasional abundance, Moles also are similar to shrews, but grasshoppers, butterfly and moth lar- shrews may have a strong, although are usually larger and have enlarged vae, ichneumonid wasps, crickets, spi- temporary, negative impact on mouse front feet. Both shrews and moles are ders, snails, earthworms, slugs, or insect populations. Many predators insectivores, whereas mice are rodents. centipedes, and millipedes. Shrews kill shrews, but few actually eat them. Worldwide, over 250 species of shrews also eat small birds, mice, small Owls in particular consume large are recognized, with over 30 species snakes, and even other shrews when numbers of shrews. recognized in the United States, the US the opportunity presents itself. Seeds, Some shrews exhibit territorial behav- Territories, and Canada (Table 1). Spe- roots, and other vegetable matter are ior. Depending on the species and the cific identification of shrews may be also eaten by some species of shrews. habitat, shrews range in density from 2 difficult. Taxonomists are still refining to 70 individuals per acre (1 to 30/ the phylogenetic relationships between General Biology, hectare) in North America. populations of shrews. Consult a Reproduction, and regional reference book on mammals, Behavior or seek assistance from a qualified Damage mammalogist. Shrews are among the world’s small- Most species of shrews do not have est mammals. The pigmy shrew (Sorex significant negative impacts and are Range hoyi) is the smallest North American not abundant enough to be considered mammal. It can weigh as little as 0.1 pests (Schmidt 1984). Shrews some- Shrews are broadly distributed ounce (2 g). Because of their small size, times conflict with humans, however. throughout the world and North shrews have a proportionally high sur- The vagrant shrew (Sorex vagrans) has America. For specific range informa- face-to-volume ratio and lose body been reported to consume the seeds of tion, refer to one of the many refer- heat rapidly. Thus, to maintain a con- Douglas-fir (Pseudotsuga menziesii), ences available on mammal distribu- stant body temperature, they have a although the seeds constitute a minor tion for your region. Publications by high metabolic rate and need to con- part of the diet. The masked shrew Burt and Grossenheider (1976), Hall sume food as often as every 3 to 4 (Sorex cinereus) destroyed from 0.3% to (1981), and Junge and Hoffmann hours. Some shrews will consume 10.5% of white spruce (Picea glauca) (1981) are particularly helpful. three times their body weight in food seeds marked over a 6-year period over a 24-hour period. (Radvanyi 1970). Lodgepole pine Habitat Shrews usually do not live longer than (Pinus contorta) seeds are also eaten by 1 to 2 years, but they have 1 to 3 litters the masked shrew. Radvanyi (1966, Shrews vary widely in habitat prefer- per year with 2 to 10 young per litter. 1971) has published pictures of shrew, ences throughout North America. Specific demographic features vary mouse (Peromyscus, Microtus, and Shrews exist in practically all terres- with the species. The gestation period Clethrionomys spp.), and chipmunk trial habitats, from montane or boreal is approximately 21 days. (Eutamias spp.) damage to lodgepole regions to arid areas. The northern wa- pine seeds, and describes shrew dam- Shrews have an acute sense of touch, ter shrew (Sorex palustris) prefers age to white spruce seeds. marshy or semiaquatic areas. Regional hearing, and smell, with vision playing reference books will help identify spe- a relatively minor role. Some species of The northern water shrew (Sorex cific habitats. A word of caution is in shrews use a series of high-pitched palustris) may cause local damage by order, however. Distribution studies squeaks for echolocation, much as bats consuming eggs or small fish at hatch- based on the results of snap-trapping do. However, shrews probably use eries. The least shrew (Cryptotis parva), research have a pronounced tendency echolocation more for investigating also known as the bee shrew, some- to understate the abundance of their habitat than for searching out times enters hives and destroys the shrews. Studies using pit traps are food. Glands located on the hindquar- young brood (Jackson 1961). The more successful in assessing the pres- ters of shrews have a pungent odor northern short-tailed shrew (Blarina ence or absence of shrews in a particu- and probably function as sexual attrac- brevicauda) has been reported to dam- lar location. tants. Blarina brevicauda, and presum- age ginseng (Panax spp.) roots. Short- ably B. carolinensis and B. hylophaga tailed and masked shrews reportedly (the short-tailed shrews), have a toxic can climb trees where they can feed on D-88 Table 1. Shrews of the United States, the US Territories, and Canada (from Legal Status Banks et al. 1987, and Jones et al. 1992). Shrews are not protected by federal Scientific name Common name laws, with one exception. The south- Blarina brevicauda Northern short-tailed shrew eastern shrew (Sorex longirostris fischeri) Blarina carolinensis Southern short-tailed shrew is protected in the Great Dismal Blarina hylophaga Elliot’s short-tailed shrew Swamp in Virginia and North Carolina Cryptotis parva Least shrew by the Endangered Species Act of Notiosorex crawfordi Desert shrew 1973. Nowak and Paradiso (1983:131) Sorex alaskanus Glacier Bay water shrew list the following additional species or Sorex arcticus Arctic shrew populations of concern: Sorex preblei, Sorex arizonae Arizona shrew Sorex trigonirostri, and Sorex merriami in Sorex bairdii Baird’s shrew Oregon; Sorex trigonirostri eionis in Sorex bendirii Pacific water or Marsh shrew Florida along the Homossassee River; Sorex cinereus Cinereus or Masked shrew and Sorex palustris punctulatus in the Sorex dispar Long-tailed or Rock shrew southern Appalachians. Sorex fontinalis Maryland or Eastern shrew Some states may have special regula- Sorex fumeus Smokey shrew tions regarding the collection or killing Sorex gaspensis Gaspe shrew of nongame mammals. Consult your Sorex haydeni Hayden’s shrew local wildlife agency or Cooperative Sorex (Microsorex) hoyi Pygmy shrew Extension office for up-to-date Sorex hydrodromus Pribilof Island shrew information. Sorex jacksoni St. Lawrence Island shrew Sorex longirostris Southeastern shrew Sorex lyelli Mt. Lyell shrew Damage Prevention and Sorex merriami Merriam’s shrew Control Methods Sorex monticolus Montane or Dusky shrew Sorex nanus Dwarf shrew Exclusion Sorex ornatus Ornate shrew Rodent-proofing will also exclude Sorex pacificus Pacific shrew shrews from entering structures. Place Sorex palustris Northern water shrew hardware cloth of 1/4-inch (0.6-cm) Sorex preblei Preble’s shrew mesh over potential entrances to Sorex sonomae Fog shrew exclude shrews. The pygmy shrew Sorex tenellus Inyo shrew (Sorex hoyi) may require a smaller Sorex trowbridgii Trowbridge’s shrew mesh. Coarse steel wool placed in Sorex tundrensis Tundra shrew small openings can also exclude Sorex ugyunak Barren ground shrew shrews. Sorex vagrans Vagrant shrew Suncus murinus House shrew Cultural Methods Regular mowing around structures should decrease preferred habitat and