References- Allred, M. 1981. The potential use of beaver population density in beaver resource management. Journal of the Idaho Academy of Science. 17(1): 14-24. Borrecco, J.E.; Black, H.C. 1990. Animal damage problems and control activities on National Forest System lands. In: Davis, L.R.; Marsh, R.E.; Beadle, D.E., eds. Proceedings, 14th vertebrate pest conference; 1990 March 6-8; Sacramento, CA. Davis, CA: University of California: 192-198. Bradt, G.W. 1947. Michigan beaver management. Lansing, Ml: Michigan Department of Conservation, Game Division. 56 p. Dyer, J.N.; Rowell, C.E. 1985. An investigation of techniques used to discourage rebuilding of beaver dams demolished by explosives. In: Bromley, P.T., ed. Proceedings, 2d Eastern wildlife damage conference; 1985 September 22-25; Raleigh, NC. Raleigh, NC: North Carolina State University: 97-120. Fisher, P.H. 1986. Keeping beavers from plugging culvert inlets. Engineering Field Notes. Washington, DC: U.S. Department of Agriculture, Forest Service. 18: 9-13. Fitzgerald, W.S.; Thompson, R.A. 1988. Problems associated with beaver in stream or floodway management. In: Crabb, A.C.; Marsh, R.E., eds. Proceedings, 13th vertebrate pest conference; 1988 March 1-3; Monterey, CA. Davis, CA: University of California: 190-195. Hill, E.P. 1982. Beaver (Castor canadensis). In: Chapman, J.A.; Feldhamer, G.A., eds. Wild mammals of North America: biology, management, and economics. Baltimore, MD: Johns Hopkins University Press: 256-281. Medin, D.E.; Torquemada, K.E. 1988. Beaver in western North America: an annotated bibliography, 1966 to 1986. Gen. Tech. Rep. INT-242. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 18 p. Owen, C.N.; Adams, D.L.; Wigley, T.B. 1984. Inefficacy of a deer repellent on beavers. Wildlife Society Bulletin. 12: 405-408. Provost, E.E. 1958. Studies on reproduction and population dynamics in beaver. Pullman, WA: Washington State University. 78 p. Ph.D. dissertation. Roblee, K.J. 1983. The use of corrugated plastic drainage tubing and wire mesh culverts for controlling water levels at nuisance beaver sites. In: Decker, D.J., ed. Proceedings, 1st Eastern wildlife damage control conference; 1983 September 27-30; Ithaca, NY. Ithaca, NY: Cornell University, Cooperative Extension: 56-57. Roblee, K.J. 1987. The use of T-culvert guard to protect road culverts from plugging by beavers. In: Holler, N.E., ed. Proceedings, 3d Eastern wildlife damage control conference; 1987 October 18-21; Gulf Shores, AL. Auburn, AL: Auburn University, Cooperative Extension: 25-41. Wigley, T.B., Jr. 1981. A model of beaver damage and control. State College, MS: Mississippi State University. 151 p. Ph.D. dissertation. Nutria (Myocaster copypu) Description-These semiaquatic rodents are native to South America. They resemble beavers but have long round tails. Males sometimes weigh as much as 20 pounds, but most adults weigh about 8 pounds. Their hind feet are webbed between the inner four toes. Economic significance-Nutria may cause damage to newly planted cypress seedlings and are a deterrent to natural regeneration of cypress in some flooded areas of the Southeastern United States. They also may cause minor damage to Douglas-fir plantations in western Oregon and Washington. Life history information- Preferred habitat-Wetlands and flooded areas provide ideal habitat. Through escape from fur farms and distribution by fur trappers, nutria have established substantial populations in Oregon and Washington, North Carolina to Maryland, and Alabama to Texas. Wild populations have been reported in at least 40 States. Feeding habits-Nutria commonly feed on the basal parts of soft grasses or aquatic plants. They may eat several pounds of food daily. Activity--When alarmed on land, these animals splash into water and may remain hidden in aquatic vegetation. Like muskrats, they build feeding platforms of discarded plant parts. They may dig extensive burrow systems and are primarily nocturnal animals. Reproduction-Nutria breed throughout the year; litter size averages five young, after a 130-day pregnancy. Newborns are fully furred, with their eyes open and can swim immediately. Damage problems and their management-Nutria have been damaging newly planted cypress seedlings in Louisiana since the late 1940s. By 1960, the problem was so serious that the USDA Soil Conservation Service recommended that further plantings be suspended until a control method was available. In a 1985 test, plastic seedling protectors were chewed through at the water level, the seedlings were clipped and dropped and the taproots pulled out. The taproot bark and root collars were eaten. All seedlings were destroyed within 8 weeks. Chickenwire fences pro- vided excellent protection from nutria in dry areas. Individual wire tubes for use as seedling protectors were found to be difficult to make and install. Zinc phosphide is the only Federally registered toxicant for use in nutria control and usually is used with fresh carrot bait, after prebaiting. Baiting procedures are difficult and must be carefully followed for effectiveness and safety. Forest Service personnel should consult with their wildlife biologist, Regional Office pesticide-use specialist, or APHIS-ADC personnel for the latest control recommendations before initiating control practices. In some states, nutria are protected furbearers; consult state wildlife officials before initiating controls. 119 References- Connor, W.H.; Toliver, J.R. 1987. The problem of planting Louisiana swamplands when nutria (Myocaster coypu) are present. In: Holler, N.R., ed. Proceedings, 3d Eastern wildlife damage control conference; 1987 October 18-21; Gulf Shores, AL. Auburn, AL: Auburn University, Cooperative Extension: 42-49. Evans, J. 1983. Nutria. In: Timm, R.M., ed. Prevention and control of wildlife damage. Lincoln, NE: University of Nebraska, Cooperative Extension: B-61 to B-70. Evans, J. 1987. Vexar seedling protectors did not reduce nutria damage to planted bald cypress seedlings. Tree Planters Notes. 38(3): 26-29. Willner, G.R. 1982. Nutria. In: Chapman, J.A.; Feldhamer, G.A., eds. Wild mammals of North America: biology, management, and economics. Baltimore, MD: Johns Hopkins University Press: 1059-1076. Meadow Voles Description-Meadow voles (also known as field (Microtus spp.) mice) are mostly brownish gray, with dense fur, beady eyes, small ears, and relatively short tails. The several species of meadow voles differ widely in size; the combined length of their heads and bodies ranges from 2 to 5 inches. Vole presence is indicated by 1/2-inch-wide runways through matted grass. Further evidence includes small piles of droppings and short clippings of grass along these runways. Lemmings, tree voles, and redback voles may be confused with Microtus spp. Individual species coloration is the main distinguishing factor. Economic significance-Meadow voles eat conifer seeds, newly germinated seed- lings, and bark of young trees. They can cause serious damage to conifer plantations, especially where snow occurs in winter. Meadow voles also are detrimental to many agricultural crops during periods when their populations are high. Life history information- Preferred habitat-Meadow voles occur in a variety of sites with sufficient vegetation to provide food and cover. Grassy areas provide the most desirable habitat. Feeding habits-All types of vegetation, including grass, herbaceous foliage, twigs, roots, seeds, and bark, are eaten. Activity--Meadow voles are active both day and night throughout the year. Their pre- sence is readily detected by distinct winding runways beneath the vegetation. Each vole usually maintains its own set of runways, but its territory may be occupied by several voles. Individual home territories range from a few square feet to areas as large as 0.1 acre. Damage problems and their management- Identification-Barking of small limbs and seedlings is characterized by indistinct tooth marks and a fuzzy, roughened appearance (fig. 31). Areas of dense ground vegetation have numerous distinct runways. 120 Figure 31-Vole-barked seedlings showing typical roughened stem. Determining the need for damage management-Meadow vole populations fluctu- ate dramatically, often causing damage at high-population levels, with populations dropping after damage is noticed and before control is undertaken. When considering whether to undertake damage management, be sure to verify that a problem still exists, as the population can crash in a matter of weeks. Management methods- BaitineMeadow voles usually can be controlled with 2-percent zinc phosphide- treated grain. Distribute the bait in quantities of l/2 teaspoonful directly in runways and burrows. The quantity of bait needed per acre will differ depending on vole density and distribution and on the density of cover. Six pounds of bait per acre normally is enough to control high populations in dense cover. Correct bait placement is very important, as the voles seldom venture from the protection of their runways. Baiting is most effective in late fall. Baiting may be needed for several years in problem areas. Anticoagulants are registered for use in some states. Check with your wildlife biologist or Regional Office pesticide-use specialist to determine the status of toxicants registered in your area. Habitat man$u/atio+Removing food and cover is an effective method for con- trolling damage by meadow voles, but it may have adverse effects on other wildlife. This approach to damage control is most applicable