SHREWS Utah State University Logan, Utah 84322-5210

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 eggs or young birds in a nest or con- an introduced species to Guam. It has food, and may increase predation. sume suet in bird feeders. been reported as a host for the rat flea Where shrews are eating tree seeds, (Xenopsylla cheopis) which can carry the The pugnacious nature of shrews plant seedlings instead to eliminate plague bacillus (Yersinia pestis) sometimes makes them a nuisance damage. (Churchfield 1990). Compared to rat when they live in or near dwellings. (Rattus spp.) numbers, however, house Shrews occasionally fall into window Repellents shrew numbers are usually low, and wells, attack pets, attack birds or chip- risk of plague transmission is probably No repellents are registered for use munks at feeders, feed on stored minimal. The house shrew is accus- against shrews. foods, contaminate stored foods with tomed to living around humans and feces and urine, and bite humans when houses, which increases its damage Toxicants improperly handled. Potential exists potential. It is considered smelly and for the transmission of diseases and No toxicants are registered to poison noisy, making incessant, shrill, clatter- parasites, but this is poorly docu- shrews. ing sounds as it goes along (Church- mented. field 1990:149). On occasion it destroys The house shrew (Suncus murinus) is stored grain products.

D-89 Fumigants No fumigants are registered for use against shrews. It would be impracti- cal to use fumigants because of the porous nature of typical shrew burrows.

Trapping Mouse traps (snap traps), box traps, a and pit traps have been used to collect shrews. Set mouse traps in runways or along walls, with the traps set at a right angle to the runway and the trig- gers placed over the runway (Fig. 2a). Small box traps can be set parallel to and inside of runways, or parallel to walls around structures (Fig. 2b). Bait the traps with a mixture of peanut but- ter and rolled oats. A small amount of bacon grease or hamburger may in- crease the attractiveness of the bait. A pit trap consists of a gallon jar or a large can sunk into the ground under a runway until the lip of the container is level with the runway itself (Fig. 2c). b Bait is not necessary. A small amount of bacon grease smeared around the top of the container may be an effec- tive attractant, but this may also attract large scavengers. Pit traps are more effective for capturing shrews than snap traps, although the increased la- bor involved in setting a pit trap may not be justified when trying to capture only one or two animals. Monitor pit traps daily, preferably in the morning before the temperature gets hot, although Churchfield (1990) recom- mends checking traps four times in a 24-hour period. Place cotton wool in the pit trap containers to reduce the c mortality of trapped animals. This is especially important to ensure the suc- cessful release of nontarget animals. Since shrews are generally beneficial in consuming insects, live-captured ani- mals can be relocated in suitable habi- tat more than 200 yards (193 m) from the capture site. The traps and placement procedures described above are also effective for catching mice. Note the identification Fig. 2. Traps and trap placement for capturing shrews: a) mouse trap (snap trap) set perpen- characteristics given above for deter- dicular to wall, with trigger next to wall; b) box mining whether the captured animal is trap set parallel to wall; c) pit trap sunk in indeed a shrew. Sometimes birds are ground over runway (includes cotton wool). captured in traps set for shrews. If this

D-90 occurs, try placing a cover over the that if a shrew ran across a farm ani- Chambers, K. A. 1979. A country-lover’s guide traps, a cover over the bait, moving the mal that was lying down, the animal to wildlife. The Johns Hopkins Univ. Press, Baltimore, Maryland 228 pp. traps to another location, or omitting would suffer intense pain. To counter- rolled oats from the bait mixture. act this, a shrew would be walled up Churchfield, S. 1990. The natural history of shrews. in an ash tree (a ‘shrew ash’), and then Cornell Univ. Press, Ithaca, New York. 178 pp. Shooting a twig taken from the tree would be Fowle, C. D., and R. Y. Edwards. 1955. An brushed onto the suffering animal to unusual abundance of short-tailed shrews, Shooting is not practical and is not rec- Blarina brevicauda. J. Mammal. 36:36-41. relieve the pain. The ancient Egyptians ommended. It is illegal in some states Hall, E. R. 1981. The mammals of North America. and localities. believed the shrew to be the spirit of darkness. The shrew has also been Vol. 1. John Wiley and Sons, New York. 690 pp. Other Methods mentioned as a Zuni beast god, pro- Hoffmeister, D. F. 1967. An unusual concentration viding protection for stored grains of shrews. J. Mammal. 48:462-464. Owls may reduce local populations of from raids by rats and mice Jackson, H.H.T. 1961. Mammals of Wisconsin. shrews in poor habitats, but this has (Hoffmeister 1967). Univ. Wisconsin Press, Madison. 504 pp. not been documented. Domestic cats Jones, J. K., Jr., R. S. Hoffmann, D. R. Rice, C. appear to be very good predators of At least one tall tale involving shrews Jones, R. J. Baker, and M. D. Engstrom. 1992. shrews, although they seldom eat has been found to be true. The discov- Revised checklist of North American them (presumably because of the ery that some shrews possess a toxic mammals north of Mexico, 1991. Occas. Papers Mus. Texas Tech Univ. 146:1-23. shrew’s unpleasant odor). Cats may be venom confirms stories about the effective at temporarily reducing local- poisonous bite of shrews. Junge, J. A., and R. S. Hoffmann. 1981. An annotated key to the long-tailed shrews ized shrew populations living in poor The etymology of the word shrew is (genus Sorex) of the United States and cover around structures. Cat owners also interesting. The Old English form Canada, with notes on Middle American may find dead, uneaten shrews of the word was screawa, or shrew- Sorex. Univ. Kansas, Mus. Nat. Hist., Occas. brought inside the home. Rather than mouse. The Middle English form was Papers 94:1-48. reduce the shrew population outside shrewe, meaning an evil or scolding Martin, I. G. 1981. Venom of the short-tailed to prevent this, simply monitor loca- person. Thus shrew has a double shrew (Blarina brevicauda) as an insect immobilizing agent. J. Mammal. 62:189-192. tions regularly used by your cat, and meaning. It defines the small mammal dispose of dead shrews by placing a as well as an ill-tempered, scolding hu- Nowak, R. M., and J. L. Paradiso. 1983. Walker’s plastic bag over your hand, picking up mammals of the world. Vol. 1. The Johns man (usually female). Hopkins Univ. Press, Baltimore, Maryland. the dead animal, turning the bag 568 pp. inside out while holding the shrew, Shrews are in the family Soricidae. sealing the bag, and discarding it with Soricis is the genitive form of sorex, a Radvanyi, A. 1966. Destruction of radio-tagged Latin word for shrew-mouse. seeds of white spruce by small mammals the garbage. Using a plastic bag in this during summer months. For. Sci. 12:307-315. manner reduces the potential for flea, Radvanyi, A. 1970. Small mammals and tick, helminth parasite, or disease Acknowledgments regeneration of white spruce forests in transmission. western Alberta. Ecol. 51:1102-1105. I appreciate the assistance and comments of C. Radvanyi, A. 1971. Lodgepole pine seed Economics of Damage L. Shugart, S. E. Hygnstrom, and four anony- depredation by small mammals in western mous reviewers while developing this manu- Alberta. For. Sci. 17:213-217. and Control script. L. Thomas and J. Shepard provided up-to-date information on the legal status of Schmidt, R. H. 1984. Shrew damage and control: Sorex longirostris fischeri. a review. Proc. Eastern Wildl. Damage No studies concerning the economics Control Conf. 1:143-146. Figure 1 is reproduced with permission from of shrew damage and control are avail- Schwartz and Schwartz (1981). Schwartz, C. W., and E. R. Schwartz. 1981. The able. In Finland, shrews appear to play wild mammals of Missouri, rev. ed. Univ. a more important role as predators of Figure 2 was drawn by Jill Sack Johnson. Missouri Press, Columbia. 356 pp. conifer seeds than they do in North Tomasi, T. E. 1979. Echolocation by the short- America. Overall, the economics of For Additional tailed shrew Blarina brevicauda. J. Mammal. 60:751-759. damage by shrews is not considered Information great. Banks, R. C., R. W. McDiarmid, and A. L. Gardner, eds. 1987. Checklist of vertebrates Folklore and Etymology of the United States, the US Territories, and Editors Canada. US Dep. Inter, Fish Wildl. Serv., Scott E. Hygnstrom Chambers (1979) reviewed some Resour. Pub. 166. 79 pp. Robert M. Timm Gary E. Larson aspects of shrew biology and folklore: Burt, W. H., and R. P. Grossenheider. 1976. A At one time in Europe it was thought field guide to the mammals. Houghton Mifflin Co., Boston. 289 pp.

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