Habitat Use by Meso-Predators in a Corridor Environment Author(s): S. Nicole Frey and Michael R. Conover Reviewed work(s): Source: The Journal of Wildlife Management, Vol. 70, No. 4 (Aug., 2006), pp. 1111-1118 Published by: Allen Press Stable URL: http://www.jstor.org/stable/3803478 . Accessed: 18/04/2012 18:10 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Allen Press is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Wildlife Management. http://www.jstor.org ResearchArticle Habitat Use by Meso-Predators in a Corridor Environment S. NICOLEFREY,1'2 Jack H. BerrymanInstitute, Department of Forestry,Range and WildlifeSciences, UtahState University, Logan,UT 84322-5230, USA MICHAELR. CONOVER,Jack H. BerrymanInstitute, Department of Forestry,Range and WildlifeSciences, UtahState University, Logan,UT 84322-5230, USA Abstract Red foxes (Vulpesvulpes), raccoons (Procyonlotor), and striped skunks(Mephitis mephitis) are found throughoutthe UnitedStates, wherever there is suitable denning habitatand food resources. Densities of these predators have increased throughoutthe IntermountainWest as a consequence of humanalterations in habitat. Withinthe Bear RiverMigratory Bird Refuge (hereafter,refuge), in northernUtah, USA, upland nesting habitatfor ducks is limitedto the levee banks and roadsides. Red foxes, raccoons, and striped skunks, whichprey on uplandnesting birds,are also abundanton the refuge. We studied red foxes, raccoons, and striped skunks'use of levees and the edges associated withthem withina wetlandenvironment. Red fox, raccoon, and stripedskunk locations were negativelycorrelated with distance to the nearest dike (-0. 78, -0.69, and -0.45, respectively).Animals incorporated more roads and/or levees into theirhome ranges than expected by chance (X= 2.6; Z < 0.001); incorporationof levees was greaterduring the dispersalseason thanthe rearingseason (P = 0. 03). Skunkhome ranges (averagesize, 3.0 km2)were oriented along roads and levees (P = 0.03), whereas raccoon (averagesize, 3.6 km2) and fox home ranges (averagesize, 3.5 km2) were not (P = 0.93, P = 0. 13, respectively).Fox home ranges in the refuge were more oblong in shape than reported elsewhere (P = 0.03). However,home-range shapes of raccoons and striped skunks were similarto previous studies (P = 0.84, P = 0.97, respectively).The use of roads and levees within the refuge increases the possible travel distance and penetration of predators into wetland environments. This contributesto increased depredationof waterfowlnests and to decreased recruitment.Managers of similarareas might decrease depredation of waterfowlby disruptingthe linearpattem of corridors,thereby decreasing the congestion of animal roads and levees. This would, then, decrease the encounter rates of predatorsand prey. (JOURNALOF WILDLIFEMANAGEMENT 70(4):1111-1118; 2006) Key words Corridors,habitat use, linearhabitat, predators, raccoon, red fox, striped skunk, waterfowl. Historically, in the Intermountain West of the United States, Halpin and Bissonette (1988) noted that foxes used roads and suitable denning and foraging habitat for red foxes and raccoons trails to travel through habitat when there was snow cover. was limited. Much of this region was characterized by dry, arable Similarly, raccoons usually display directed foraging, moving along land, dominated by sagebrush and grasses (Foote 1989, Wagner edges and corridors to access a hunting area (Urban 1970, 1995). However, human settlement of the land in the Inter- Hoffman and Gottschang 1977, Ough 1979). The use of roads mountain West, especially irrigated agriculture, increased the may be more pronounced in flooded marshes because predators distribution of water throughout the dry landscape. Subsequently, may be able to move much faster, with less energy expenditure, by on levees rather than marshes. populations of red foxes and raccoons increased in Utah, USA, traveling wading through of waterfowl and birds use areas although neither species was native to the area (Durrant 1952, Many species game upland Zeveloff 1988, Garrettson et al. 1996). adjacent to wetlands for nesting (Greenwood and Sovada 1996). For wetlands such as the Bear River Bird Federal and state wildlife management agencies in Utah, USA, Migratory Refuge, which was created a of levees, habitat is often developed several waterfowl management areas during the early by system upland restricted to the levees and the roads built on of them. These 1900s, principally around river deltas flowing into the Great Salt top areas also concentrate alternative for mammalian Lake (GSL). Often, the wetland refuges were created by may prey such as small mammals and invertebrates. Thus, developing levees to impound river water coming into the GSL. predators, increased depredation of nesting birds or eggs at times may be Originally created as oases for migratory birds, these wetlands an opportunistic response to a resource found while searching for have also become a haven for meso-predators, which prey upon other prey in the same area (Cowardin et al. 1983). When nesting migratory and nesting birds, their nests, and their young. areas consist entirely of linear strips of habitat along dirt roads and Agricultural field edges, footpaths, roads, right-of-ways, and levee banks, there is an increased chance of hens similar into a habitat serve as corridors for predators locating openings may and their nests while the area. access into an environment moving through predators, increasing (Askins 1994, Few studies on mammalian corridor use have focused on small- Urdang 1995). Furthermore, such corridors may serve to attract to medium-sized predators. Previous studies of predator-prey and funnel into an area, predators thereby increasing prey exposure interactions along corridors suggest that the predator use of and risk (Kuehl and Clark 2002). Ease of travel small provided by human trails and roads increases the depredation rate of prey roads or increases travel can hunt paths predator speed; thus, they (Trewhella and Harris 1990, James and Stuart-Smith 2000). Our more in less time. ground objective was to determine how red foxes, raccoons, and striped 1 skunks use levee roads, and the edges associated with them, within E-mail: [email protected] 2 a wetland environment. We that if red Present address: Jack H. Berryman Institute, USU Extension, hypothesized foxes, Biology Department, Southern Utah University, Cedar City, UT raccoons, and striped skunks were attracted to levees and dirt 84720, USA roads, their home range might reflect a linear shape. Additionally, Frey and Conover * Predators in a CorridorEnvironment 1111 their home reflect the to ranges might propensity incorporate 200 - roads into space-use patterns. If predators are using similar 180 --Fox vegetation types as upland nesting waterfowl, as well as increasing Raccoon 160 -- their use of habitat via roads and levees, then there might be an --Skunk -- increased potential for predators to impact waterfowl recruitment. 140 Random 120 - Area Study S100 -- The Bear River Migratory Bird Refuge was created in 1928 from 80 the delta of the Bear River, near the northeastern end of the GSL, 60 Utah, USA. The with more than 65,000 ha of wetlands, • refuge, S40 was created to increase and for feeding breeding grounds 20 migratory birds. We conducted our study in the delta section of the which contained ha of wetland habitat. refuge, >26,000 100 200 300 400 500 600 700 800 900 1000 Historically, this area supported the highest densities of nesting Distance from levy (m) waterfowl before the GSL flood. This section of the refuge was created by a system of levees that control the flow of the Bear 1. Number of locations of red foxes, raccoons, and skunks River into the GSL (Williams and Marshall 1938; 1). The Figure striped Fig. locatedwithin 1,000 m fromthe nearestlevee or road,Bear River Migratory topography was relatively flat, falling approximately 0.1 m/km to BirdRefuge, Utah, USA, 2000-2002. the south, with most elevation at 1,280 m. The area experienced moderate spring and fall seasons, with dry hot summers and short, with a numbered tag. We only fitted raccoons and foxes weighing cold winters. Summer temperatures often exceed 38'C, whereas >5 kg and skunks weighing >1.5 kg with a radiocollar (Advanced winters sometimes fell below -23?C. The average annual Telemetry Systems, Isanti, Minnesota) to minimize the collaring precipitation ranged from 29 cm in the eastern side of the refuge of subadults (Major and Sherbourne 1987, Gehrt and Fritzell to 31 cm in the western portion (A. Trout, U.S. Fish and Wildlife 1998). Upon recovery from the tranquilizer, the animals were Service, unpublished report). released on-site. We conducted trapping periodically to maintain a Before the delta of the was the 1983, refuge predominant base level of 10 radiocollared animals per species. area for most of the duck within the nesting species nesting refuge, We radiotracked animals throughout the day by dividing the day and other avian there and many species foraged (Williams into 3 time periods: