Habitat Use by Meso-Predators in a Corridor Environment Author(S): S

Home , Striped Skunk

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

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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: 1) 0800-dusk, 2) dusk to midnight (in winter, Marshall The annual waterfowl 1938). average production during this time period was usually from 1800 to 2400 hours), and 3) 1953-1964 was and coots 41,000 ducklings, 2,000 goslings, 8,000 midnight to dawn (this period was usually from 2400 to 0600 (A. F. Halloran, United States Fish and Wildlife Service, hours, extending to 0700 at the longest part of winter). During In 1983, the GSL flooded, the unpublished report). covering each daylight radiotracking session, we visually located animals. refuge with salt water for more than 7 years and destroying most Upon locating the animal, we recorded its position using a of the dikes along with all vegetation (Foote 1989). handheld Global Positioning System (GPS) unit (Magellan During the time that the refuge was under water, red foxes and Tracker, Thales Navigation, Inc.). During each nocturnal radio- raccoons, which were previously rare in the area, set up residence tracking session, we estimated animals' locations using triangu- around the refuge. As a consequence of the flood and the arrivalof lation (Mech 1983). these new as few as 100 were predators, ducklings per year To the we drove the levees to find a the 2000 season at the as triangulate study animals, produced during nesting refuge, a we a for the with historical levels of more than 79,000 in 1964 (A. F. frequency. Upon hearing signal, acquired bearing compared animal. We then drove to another location to obtain a second Halloran, unpublished data). During our study, mammalian bearing. We obtained 2-3 bearings for each location; 3 predators were identified as the main predators of duck nests at bearings were We obtained within 10 the refuge. Therefore, refuge managers believed mammals to be preferred. subsequent bearings minutes of the last to minimize the error attributed to the primary impediment preventing waterfowl production from bearing, animal movement. were also >200 and <1600 from returning to historic levels. Bearings apart each other to further minimize error (Kitchen et al. 2000). There Methods were times when travel by motor vehicles affected the movements Establishing Predator Locations of the radiocollared animals; therefore, we discarded locations characterized with sudden movements We trapped and radiocollared red fox, raccoon, and striped skunk predator (Ellis 1964). We the software from December 1999 to February 2000. We trapped foxes using analyzed triangulated bearings using package neck snares, with deer stops fixed to them, and with foothold traps Locate (Pacer, Truro, Nova Scotia, Canada) to obtain an (Meia and Weber 1995). We trapped raccoons and skunks with estimated location for a particular animal. Locate established an box traps baited with commercial cat food (Endres and Smith error estimate for locations determined by 3 points. We deleted all 1993). To handle the trapped animals, we tranquilized each estimated locations with an associated error >100 m. In addition, animal using 0.1 mg/kg of an acepromazine/ketamine mixture we randomly placed test collars, which were collars unattached to (0.01 mg acepromazine and 0.09 mg ketamine; Bigler and Hoff animals, in the refuge so that estimation error for each technician 1974). We then sexed, weighed, and ear-tagged trapped animals could be established. Each technician triangulated test collars

1112 The Joumal of WildlifeManagement * 70(4) twice a year to maintain a level of integrity through minimal To determinethat, we comparedthe observednumber of roads triangulationerror. and levees within an animal'shome range on the refuge to the expectednumber of roads.Using ArcView(ESRI), we estimateda LinearAspects of Use home range area for each study animal (95% minimum convex Correlation with levees and roads.-We investigatedthe for the and season. We defined the between the number of animals found and the polygon) rearing dispersal relationship season as March 15; the season lasted distance from the nearest To avoid bias created rearing 15-July dispersal levy. any by fromJuly 15-November15 (Kitchenet al. 2000). For each home error, we the locations of red foxes, telemetry only analyzed range, we determinedthe number,length (km), and location of raccoons,and striped skunks that we found visuallyduring the roadsthat were used within a home To estimate Visual observations were exact whereas we range. expected day. locations, we 10 onto a of the and estimatedthe of locations use, randomlyplaced polygons map refuge majority nighttime using triangulation. its andwe calculatedthe of levees each We establishedvisual locations to find the roads, length overlappedby by using radiotelemetry Each a home of 3.5 location of the within the Once we polygon. polygon represented range km2, approximate animal refuge. which is the size of a fox and raccoonhome detecteda we walkedor canoedtoward the of average rangewithin radiosignal, origin the to the scaleof the of the the until we a visual of the refuge(Frey 2004), map refuge.Next, signal acquired sighting targetanimal. we conducteda the We used a handheldGPS to recordthe animal'slocation at the signed-rank,nonparametric t-test, comparing relationshipof the levees (no. of roads used, total kilometersof time that it was sighted.Often, we found animalswhile they were roads, location of home range) in the randomlycreated home sleepingor in dens. However,sometimes we spottedan animalas ranges to those of the observedhome ranges.We repeatedthis it arose from its resting spot. When this occurred,we walkedto process10 times for comparison. where the animalwas when we first sighted it, and we took the Orientation of home ranges.-We also evaluatedthe im- GPS locationfrom that spot. However,sometimes when tryingto of the locationof a roador trailwithin each home obtain a visual location,it became the portance range. apparent,through bearing Roads and trails be into the home estimates, that the animal was we may randomlyincorporated target moving, although or animals orienttheir home aroundroads. For couldn'tsee it. In those circumstances,we did not recorda visual ranges, may ranges each home we determinedthe axis, which was the location,and we did not use that datain analysisof locationto the range, largest nearestroad. longest straightline that could be drawnthrough the home range. we measuredthe created the of this axis Once we collected the locations,we examinedthe distanceof Then, angle by crossing with the nearestroad. In the event that >1 roadwas each animal'slocation to the nearestlevee of the refuge, using incorporated into a home we used the measurementfor the intersection GIS/ArcInfo (ESRI, Redlands,California). First, we calculated range, of the axiswith the roadwithin the home If home the distance from each visually sighted location to the nearest longest range. were oriented in the habitat relativeto road,regardless of the road'scondition or use. Then, we grouped ranges randomly roads, then the mean between this created axis and the road those distances into 10-m intervals,up to 1,000 m from the angle in the home shouldbe with a from nearestroad, and we calculatedthe numberof locationsin each incorporated range 450, range interval.We chose 10 m as the distanceinterval because that was 0O(parallel) to 900 (perpendicular).If home rangeswere oriented the mean betweenthe axisand the the averagewidth of a levee and its banks;thus, distancesof 0-10 along roads, angle incorporated m from a roadwould indicateanimals located on a levee.Next, we roadwould be similarto 00; home rangesarranged perpendicular to roadswould have a similarto 900. we conducteda nonparametriccorrelation test of intervaldata, using mean angle Therefore, conducted a t-test to determine PearsonCorrelation Coefficients in StatisticalAnalysis Software signed-rank nonparametric whether axes were oriented aroundroads (Version8, SAS Institute,Cary, North Carolina)to determinethe home-range randomly and trails oriented roads < or oriented relationshipbetween the number of locations found in each (j = 450), along (j 45') > intervaland the distancefrom the nearestlevee. We hypothesized awayfrom roads(Y 450). that the numberof animalsin each intervalwould decreaseas the Shape of home range.-If the study animalsfrequently used distancefrom the nearestlevee increased. roadsand areasnear them, their home rangesshould reflectthat. If there was a correlationbetween the roads and locations, it If a predatormakes extensiveuse of levees and roads, its home could have been an effect of the distributionof roads.Therefore, range should be linearlyshaped. To determinewhether animals using a random-numbergenerator, we createda subset of 500 within the refugewere using roadsextensively, we measuredthe locations to comparewith the distributionof actual locations. length-to-widthratio of each red fox, raccoon,and stripedskunk Following the same procedure for fox, raccoon, and skunk home range(95% minimumconvex polygon). A circularor square locations,we calculatedthe numberof randomlocations within home-rangeshape would have a ratio close to 1. The more linear each 10-m interval.Then, we executed a Pearson Correlation the shapeof the home range,the largerthe length-to-widthratio Coefficients test to determine this subset's relationshipwith would be. To comparethe findings of the home-rangeshape of distancefrom the nearestlevee. Finally,we comparedthe random the refuge to other regions of the world, we examinedliterature location data set with the locations of red foxes, raccoons,and concerninghome ranges, territories,and habitat use for foxes, stripedskunks in the refuge, using a Mann-Whitney U test for raccoons,and stripedskunks (Table 1). We used only articleswith nonparametricstatistics. figuresof home rangesfor analysis.For each figure,we measured Incorporation of roads into home ranges.-The numberof the length and width of the printedhome range, in millimeters. roadsincorporated into an individual'shome rangemay reflect the Then, we created a length-to-width ratio from those measure- extent to which predatorsprefer home rangesthat containroads. ments, for comparison.

Freyand Conover* Predatorsin a CorridorEnvironment 1113 Table 1. Published literatureused to establish mean length-to-widthratios for home-range shape-comparisons of red foxes, raccoons, and striped skunks. Species Reference xtratio Region Setting na Raccoon Fritzell(1978) 1.46 N.D. Rural 8 Raccoon Gehrt and Fritzell(1998) 1.66 Tex. Rural 3 Raccoon Jordan (1986) 1.36 Md. Rural 11 Raccoon Slate (1985) 2.29 N.J. Suburban 19 Red fox Adkins and Scott (1998) 2.13 Toronto, Canada Suburban 4 Red fox Coman et al. (1991) 2.00 Victoria,Australia Rural 4 Red fox Harris(1980) 1.50 Bristol,United Kingdom Urban 8 Red fox Hough (1980) 1.42 Oxford, United Kingdom Urban 4 Red fox Jones and Theberge (1982) 3.00 B.C., Canada Rural 4 Red fox Klett(1978) 2.22 La. Rural 4 Red fox MacDonaldand Newdick (1980) 2.14 Oxford,United Kingdom Urban 10 Red fox Meek and Saunders (2000) 2.47 N.S.W., Australia Suburban 5 Red fox Meia and Weber (1995) 1.63 Switzerland Rural 4 Red fox Pandolfiet al. (1997) 1.85 Italy Rural 5 Red fox Phillipsand Catling(1991) 1.87 SE Australia Rural 5 Red fox Poulle et al. (1994) 1.55 France Rural 5 Red fox Sargeant (1972) 1.56 Minn. Rural 3 Red fox Saunders et al. (2002) 1.72 N.S.W., Australia Rural 8 Red fox Schloeder (1988) 1.42 W.Va. Rural 3 Red fox Sunquist (1989) 1.80 Fla. Rural 4 Red fox Travainiet al. (1993) 1.31 Spain Rural 7 Red fox Tsukada (1997) 1.75 Japan Rural 6 Red fox White et al. (1996) 1.71 Bristol,United Kingdom Urban 5 Striped skunk Bixlerand Gittleman(2000) 3.54 Tenn. Rural 12 Striped skunk Lariviereand Messier (1998) 1.78 Sask., Canada Rural 18 a Abbreviation:n, number of home ranges.

Using past studies, we measured 98 red fox home ranges in 16 Figs. 1, 2). Randompoints were distributeddifferently than actual regions of the world in urban, suburban, and rural settings. red fox (df= 1, U= 2,945, P= 0.004), raccoon(df= 1, U= 2,793, Additionally, we measured the shapes of 41 raccoon home ranges, P = 0.06), and skunk (df = 1, U= 3,090, P= 0.001) locations. from 5 regions in North America, in rural and suburban settings. Incorporation of roads.-Within the refuge, actual home Published literature of striped skunk home ranges was scarcer; ranges incorporatedan average of 2.5 roads, whereas mean therefore, we used only 30 home ranges from 2 studies, in 2 expected home range incorporated1.3 roads. The difference regions of North America. Both were in rural settings (Table 1). betweenactual and randomlylocated home rangeswas significant Next, we conducted an ANOVA using Statistical Analysis (X2= 38.32, df= 7, P < 0.001). Red fox, raccoon,and striped skunk home Software (SAS) to compare the length-to-width ratios of home rangesincorporated a similarnumber of roadswithin their for each from our with those calculated from ranges species study home ranges(F= 0.40, df= 2, P= 0.68; Fig. 3). The studyanimals the this allowed us to determine whether the of literature; shapes incorporatedmore roadswithin home rangesduring the dispersal the home of our animals differed from those ranges study reported seasonthan in the rearingseason (F= 5.30, df= 1, P= 0.03; Fig. 3). in past studies. Results 50 Fox LinearAspects of Use • 45 Distance from levee or road.-For each species, we found 450 Raccoon most locations within m of the nearest levee. There were 40 -•M 1,000 35 -r--ISkunk 418 raccoon locations (99.5% of all locations) within 1,000 m 3 Random day .a 30 of the nearest levee. There was a inverse correlation strong 25 between the distance from the nearest levee and the number of _ 20 raccoon locations. In other words, we counted fewer animals as the E 15- distance interval increased (r = -0.69, P < 0.001; Figs. 1, 2). We found similar results for red foxes. We recorded 418 locations 10 5 (100%) for foxes within 1,000 m of the nearest levee. Fewer fox locations occurred as the distance from the levee increased (r = 10 20 30 40 50 60 70 80 90 100 -0.78, P < 0.001; Figs. 1, 2). We recorded 237 locations (100%) for skunks within 1,000 m of the nearest levee. We found fewer Distance from nearest levy (m) skunk locations as the distance from a levee increased (r = -0.45, P < 0.0001; Figs. 1, 2). Figure 2. Number of locations of red foxes, raccoons, and striped skunks In contrast, there was no correlation to the number of random located within 100 m of the nearest levee or road, Bear River MigratoryBird locations found within each distance interval (r = -0.19, P= 0.54; Refuge, Utah, USA, 2000-2002.

1114 The Joumal of WildlifeManagement * 70(4) - 4.5 II homerange 4- - 3.5- roads and levees 3 1 2.5

S1.5 0.5 0 Fox Raccoon Skunk Fox Raccoon Skunk

Rearing Dispersal

Figure3. Meannumber of roadscontained within home ranges by redfoxes, raccoons,and striped skunks on BearRiver Migratory Bird Refuge, Utah, USA, 2000-2002. 2 0 2 4 Kilometers

Red fox home rangesincorporated 3.5 km of roadsduring the dispersalseason and 3.4 km of roads during the rearingseason Figure4. Locationof foxhome ranges (95% minimum convex polygon) during (Table2, Fig. 4). Raccoonhome rangesincorporated an averageof the rearingseason in relationto the roadsand levees presenton BearRiver Bird Utah,USA, 2000-2002. 7.1 km of roadsduring the dispersalseason and 3.3 km duringthe Migratory Refuge, rearingseason (Table 2, Fig. 5). Additionally,skunks had, in their home ranges,an averageof 5.2 km of roadsduring the dispersal figuredin previousstudies (t = -0.21, df = 65, P = 0.84; t = 0.04, seasonand 3.2 km duringthe rearingseason (Table 2, Fig. 6). The df = 20, P = 0.97; respectively). of roads into the home of each length (km) incorporated ranges Discussion species was similar(F = 0.51, df = 2, P = 0.61). Study animals incorporatedmore kilometersof roads into home rangesduring Use of Levees and Roads the dispersalseason than the rearingseason (F= 6.28, df= 1, P= Red foxes, raccoons,and striped skunks concentratedtheir day 0.02). Study animals'home ranges in the refuge incorporated activitiesto the leveesof the refuge.Additionally, roads were also more kilometersof roads than home rangesthat were randomly a focus of these predators'activities, as evidencedby the presence placedin the refuge(t= 4,893, P < 0.001). Home rangeswere not of the roadsin the animals'home ranges.During periodsof high oriented along roads for foxes (Y = 33.7', S = -4, P = 0.89), water, red foxes and stripedskunks probably relied on the dense raccoons(2 = 44.5O,S = -7, P = 0.85), or skunks(2 = 23.30, S = vegetationfound along the levees for dry, shelteredresting sites. -14.5, P= 0.34). Becauseof their abilityto travelthrough shallow water and forage Shape of home ranges.-Red fox and raccoonhome ranges for aquatic invertebratesand fish (Dorney 1954, Urban 1970), on the refuge had length-to-width ratios of 2.1 and 1.8, respectively(Table 3). Home ranges of red foxes and raccoons calculatedfrom past studieshad meanlength-to-width ratio of 1.8 i 1home range and 1.7, respectively(Table 3). Skunkhome rangesin the refuge roads and levees had mean length-to-width ratios of 2.5 (Table 3). Skunk home rangesfigured in past studieshad a meanlength-to-width ratio of 2.5 (Table 3). The length-to-widthratios of red fox home ranges in the refugewere greaterthan those figuredin previousstudies (t = 2.34, df= 32, P= 0.03). However,home rangelength-to-width ratiosof raccoonsand skunksin the refugewere similarto those

Table2. Meankilometers of roadsincorporated into raccoon, red fox, striped skunkhome ranges, by season,compared with the expectedvalue, Bear River MigratoryBird Refuge, Utah, USA, 2000-2002. Factor Season n polygons R SE Raccoon Rearing 12 3.3 1.1 12 7.1 1.4 Dispersal 2 0 4 Kilometers Redfox Rearing 11 3.4 0.5 Dispersal 8 3.5 0.5 Stripedskunk Rearing 7 3.2 0.7 5 5.2 2.2 Figure5. Locationof raccoonhome ranges (95% minimum convex polygon) Dispersal the season in relationto the roadsand levees on Bear Expected - 90 2.3 0.2 during rearing present RiverMigratory Bird Refuge, Utah, USA, 2000-2002.

Freyand Conover* Predatorsin a CorridorEnvironment 1115 foraging opportunities for predators there. Additionally, wetland home range edges provided a diverse array of prey items (Greenwood et al. roads and levees 1999), which may have increased the attractiveness of this habitat for striped skunks (Phillips et al. 2003). The shallow water along the edges of the levees also provided the opportunity for raccoons to capture carp and, consequently, would be an area for scavenging by skunks and red foxes. Therefore, it is logical to determine that these predators were continuing to use the areas close to the levee banks even after they awoke. The levee banks were also the only source of upland habitat available for den sites within the refuge. During late spring-early summer, when mothers were denning and before young animals left the dens, parental red foxes, raccoons, and striped skunks would necessarily be restricted to the levee banks during the day. This may have impacted our results slightly. The effect of denning 2 0 2 4 Kilometers was limited by the fact that we collected data year-round, not just during the rearing season. Additionally, only a fraction of our study animals (females of each species and male foxes) were involved in Those animals not for Figure 6. Location of striped skunk home ranges (95% minimum convex rearing young. responsible polygon)during the rearingseason in relationto the roads and levees present rearing young would not necessarily be limited to the levee banks on Bear RiverMigratory Bird Refuge, Utah, USA, 2000-2002. during the birthing and early rearing periods. The use of these roads and trails while foraging may have raccoons were probably less dependent on the levees during the increased the distance traveled and the amount of hunting ground high-water periods. Instead, they could spend the day resting on covered by predators in a night. That increased the opportunity for matted rushes within emergent vegetation. During low-water predators to locate and depredate foraging and nesting waterfowl periods, the majority of vegetation was found along the banks and and shorebirds. Phillips et al. (2003) suggested that patches of wet meadows, possibly contributing to the linearity of day habitat that were repeatedly selected by predators are likely to be locations and home-range shapes. efficiently searched, with high levels of depredation in those Our results only took into account day locations; however, our specific areas. If foxes, raccoons, and skunks on the refuge were study animals were active in the crepuscular and nocturnal time searching the habitat along the roads and trails within their home periods. Whereas these animals are also known to have limited range on a daily basis, the result may be an increased likelihood movements during the day, it can be said that day locations that any nest located there would be found by at least one classified as resting periods for our study animals. Although we predator. could not determine how linear the home definitively ranges Home-Range Shape would be during the night, without incorporating a large error Theoretically, a circular home range or one with a length-to- bias, we could make some inferences. width ratio of 1 would be the most energetically efficient shape in Even during times of low water, such as during summer months, terms of reaching the most area with the least movement (Ables the levees contained more suitable vegetative cover for nesting 1969). This is assuming that resources were evenly distributed ducks than other sections of the refuge, and most ducks selected across the landscape and that the predator started foraging from the levees as resting sites (Williams and Marshall 1938). Frey the center of its home range each evening. We hypothesized that (1994) determined that red foxes, raccoons, and skunks striped in linear environments, such as the refuge, resources were not were attracted to areas with (found emergent vegetation predom- distributed evenly, and predators would have a linearly shaped the levee banks), via their search for inantly along presumably home range rather than circular. However, we found that length- food. Thus, waterfowl the dikes increased the nesting along to-width ratios for raccoons and striped skunks were similar to those reported elsewhere and not linear. Yet, red foxes had higher Table 3. Comparison of home range length-to-width ratios of red foxes, length-to-width ratios on the refuge than home ranges reported and skunks from studies to Bear River Bird raccoons, striped past Migratory elsewhere. This may have occurred because red foxes used the Refuge, Utah, USA, 2000-2002. refuges roads for travel more than the other 2 predator species. Data set Predator uses of levees and roads have implications for the BRMBRa Literature success of nesting birds in managed wetlands. Historically, nesting waterfowl in the refuge used vegetation cover on the banks of the n a ratio SE n R ratio SE Species levees as nesting habitat (Williams and Marshall 1938, Crabtree Raccoon 26 1.8 0.11 41 1.8 0.15 1983). However, at the time of our study, raccoons, striped Red fox 23 2.1 0.17 53 1.7 0.08 skunks, and red foxes were making extensive use of the same Striped skunk 12 2.5 0.63 30 2.5 0.4 habitat as nesting waterfowl. Few duck nests located on the a Abbreviations: BRMBR,Bear River MigratoryBird Refuge; n, number of refuge's levees could complete nest incubation without being independent home-range polygons. located by a predator. Hence, there was little duck production in

1116 The Journalof WildlifeManagement * 70(4) the refuge during the years of our study because of high rates of Acknowledgments nest predation. We thank M. Bodenchuk and G. Cook, from United States Management Implications Department of Agriculture-Animal and Plant Health Inspection We recommend that methods to create a spatial separation Service-Wildlife Services, for guidance and instruction during the between the levee habitat used by predators and the habitat used initial trapping of the study animals. The Jack H. Berryman by waterfowl would be beneficial to the management of this refuge Institute provided funding for research, the Utah Agricultural and similar habitats. to the Essentially, managers might try disrupt Experiment Station provided funding for printing, and the Bear linear nature of the refuge to reduce the ease of travel and River Migratory Bird Refuge provided in-kind support. Our congestion of activity in these areas. Additionally, we recommend technicians were indispensable, especially M. Burrell, J. Butler- that managers interested in increasing waterfowl recruitment in and A. Brown. our volunteers were corridor environments consider methods to control predator Curl, J. Curl, Finally, numbers during the waterfowl-nesting season when the use of continually available and excited during all hours of the day and the dikes by both predators and prey are greatest. night for 3 years-M. Fitzhugh, G. Fitzhugh, and D. Viator. LiteratureCited Ables, E. D. 1969. Home range studies of red foxes. Journalof Mammalogy movements of a raccoon population in a suburban residentialcommunity. 50:108-122. Journalof Mammalogy58:623-636. Adkins, C. A., and P. Stott. 1998. Home ranges, movements and habitat Hough, N. G. 1980. The ranging behavior of a maturing female red fox, associations of red foxes, Vulpes vulpes, in suburban Toronto, Ontario, Vulpes vulpes. Pages 691-696 in C. J. Amlaner and D. W. MacDonald, Canada. Journalof Zoology (London)244:335-346. editors. A handbook on biotelemetryand radiotracking.Pergamon, Oxford, Askins, R. A. 1994. Open corridorsin a heavilyforested landscape: impact on England. shrublandand forest-interiorbirds. WildlifeSociety Bulletin22:339-347. James, A. R. C., and A. K. Stuart-Smith.2000. Distributionof caribou and Coman, B. J., J. Robinson, and C. Beaumont. 1991. Home range, dispersal wolves in relationto linearcorridors. Journal of WildlifeManagement 64:154- and density of red foxes (Vulpesvulpes) in CentralVictoria. Wildlife Research 159. 18:215-223. Jones, D. M., and J. B. Theberge. 1982. Summer home range and habitat Cowardin, L. M., A. B. Sargeant, and H. F. Duebbert. 1983. Problems and utilizationof the red fox (Vulpesvulpes) in a tundrahabitat, northwest British potentials for prairieducks. The Naturalist34(4):4-11. Columbia. Canadian Journalof Zoology 60:807-812. Crabtree, R. L., L. S. Broome, and M. L. Wolfe. 1983. Effects of habitat Jordan, R. A. 1986. Raccoon use of farmlandhabitats on Remington Farms. characteristicson gadwall nest predationand nest-site selection. Journalof Thesis, West VirginiaUniversity, Morgantown, USA. WildlifeManagement 53:129-137. Kitchen, A. M., E. M. Gese, and E. R. Schauster. 2000. Long-term spatial Dorney, R. S. 1954. Ecology of marsh raccoons. Journal of Wildlife stability of coyote (Canis latrans) home ranges in southeastern Colorado. Management 2:217-225. Canadian Journalof Zoology 78:458-464. Durrant,S. D. 1952. Mammalsof Utah, taxonomy and distribution.University Klett, S. B. 1978. Home ranges, movement patterns, habitat use and of Kansas, Lawrence, USA. interspecificinteractions of red foxes and coyotes in northwest Louisiana. Ellis,R. J. 1964. Trackingraccoons by radio. Journalof WildlifeManagement Thesis, Colorado State University,Ft. Collins, USA. 28:363-368. Kuehl, A. K., and W. R. Clark. 2002. Predator activity related to landscape Endres, K. M., and W. P. Smith. 1993. Influence of age, sex, season and features in northernIowa. Journalof WildlifeManagement 66:1224-1234. availabilityon den selection by raccoons within the Central Basin of Lariviere,S., and F. Messier. 1998. Spatial organizationof a prairiestriped Tennessee. AmericanMidland Naturalist 129:116-131. skunk population during the waterfowl nesting season. Journal of Wildlife Foote, A. L. 1989. Response of nesting waterfowlto floodingin GreatSalt Lake Management 62:199-204. wetlands. Great Basin Naturalist4:614-617. MacDonald,D. W., and M. T. Newdick. 1980. The distributionand ecology of Frey, S. N. 2004. Habitat use and movements of predators on a managed foxes (Vulpesvulpes) in urban areas. Urban Ecology 2:123-135. waterfowlrefuge. Dissertation,Utah State University,Logan, USA. Major,J. T., and J. A. Sherbourne. 1987. Interspecificrelationships among Fritzell,E. K. 1978. Habitat use by prairie raccoons during the waterfowl coyotes, bobcats, and red fox in western Maine. Journal of Wildlife breeding season. Journalof WildlifeManagement 42:118-127. Management 51:606-616. Garrettson, P. R., F. C. Rohwer, J. M. Zimmer, B. J. Mense, and N. Dion. Mech, L. D. 1983. Handbookof animalradio-tracking. University of Minnesota, 1996. Effect of mammalianpredator removal on waterfowland non-game Minneapolis,USA. birds in North Dakota. Transactions of the North American Wildlifeand Meek, P. D., and G. Saunders. 2000. Home range and movement of foxes NaturalResource Conference 61:94-101. (Vulpesvulpes) in coastal New South Wales, Australia.Wildlife Research 27: Gehrt, S., and E. K. Fritzell.1998. Resource distribution,female home range 663-668. dispersion and male spatial interactions: group structure in a solitary Meia, J. S., and J. M. Weber. 1995. Home ranges and movements of red foxes carnivore.Animal Behaviour 55:1211-1227. in central Europe:stability despite environmentalchanges. CanadianJournal Greenwood, R. J., A. B. Sargeant, J. L. Piehl, D. A. Buhl, and B. A. Hanson. of Zoology 73:1960-1966. 1999. Foods and foragingof prairieskunks duringthe avian nesting season. Ough, W. D. 1979. Influence of probabilityand magnitude of reward upon WildlifeSociety Bulletin27:823-832. raccoon foraging behavior.Thesis, Universityof Nebraska, Lincoln,USA. Greenwood, R. J., and M. A. Sovada. 1996. Prairieduck populations and Pandolfi, M., P. Forconi, and L. Montecchiari.1997. Spatial behaviourof the predation management. Transactions of the North American Wildlifeand red fox (Vulpes vulpes) in a rural area of central Italy. ItalianJournal of NaturalResources Conference 61:31-42. Zoology 64:351-358. Halpin,M. A., and J. A. Bissonnette. 1988. Influenceof snow depth on prey Phillips,M., and P. C. Catling. 1991. Home range and activitypatterns of red availabilityand habitatuse by red fox. CanadianJournal of Zoology 66:587- foxes in Nadgee Nature Reserve. WildlifeResearch 18:677-686. 592. Phillips,M. L., W. R. Clark, M. A. Sovada, D. J. Horn, R. R. Rolf, and R. J. Harris,S. 1980. Home ranges and patterns of distributionof foxes (Vulpes Greenwood. 2003. Predator selection of prairielandscape features and its vulpes) in an urbanarea, as revealed by radiotracking.Pages 685-690 in C. relationto duck nest success. Journalof WildlifeManagement 67:104-114. J. Amlanerand D. W. MacDonald,editors. A handbook on biotelemetryand Poulle, M. L., M. Artois, and J. J. Roeder. 1994. Dynamics of spatial radiotracking.Pergamon, Oxford, England. relationships among members of a fox group (Vulpes vulpes). Journal of Hoffman, C. 0., and J. L. Gottschang. 1977. Numbers, distribution,and Zoology, London 233:93-106.

Frey and Conover * Predators in a CorridorEnvironment 1117 Sargeant,A. J. 1972. Red fox spatialcharacteristics in relationto waterfowl Tsukada,H. 1997. A divisionbetween foraging range and territoryrelated to predation.Journal of WildlifeManagement 36:225-236. food distributionin the redfox. Journal of Ethology15:27-37. Saunders,G., J. Mcllroy,M. Berghout, B. Kay,E. Gifford,R. Perry,and R. Van Urban,D. 1970. Raccoonpopulations, movement patterns, and predationon deVan.2002. Theeffects of inducedsterility on the territorialbehaviour and a managedwaterfowl marsh. Journal of WildlifeManagement 34:372-382. survivalof foxes.Journal of AppliedEcology 39:56-66. Urdang,L. 1995. TheAmerican century dictionary. L. Urdang,editor. Oxford Schloeder,C. A. 1988. Homeranges, habitat selection, and activity patterns of University,New York,New York, USA. gray and red foxes in West Virginia.Thesis, West VirginiaUniversity, F. H. 1995. of naturalresources in the USA. Wagner, Ecosystemmanagement Morgantown, IntermountainWest. Utah State University, Logan, USA. Slate,D. 1985. Movement,activity, and homerange patterns members among White,P. C. L.,G. Saunders,and S. Harris.1996. Spatio-temporalpatterns of of a high-densitysuburban raccoon population.Dissertation, Rutgers home use foxes in urbanenvironments. Journal of New Brunswick,New USA. range by (Vulpesvulpes) University, Jersey, Animal 65:121-125. Sunquist,M. E. 1989. Comparisonof spatialand temporal activity of redfoxes Ecology and grayfoxes in north-centralFlorida. Florida Field Naturalist 17:11-18. Williams,C. S., and W. H. Marshall.1938. Ducknesting studies, Bear River Travaini,A., J. J. Aldama,R. Laffitte,and M. Delibes.1993. Homerange and MigratoryBird Refuge, Utah. Journal of WildlifeManagement 2:29-45. activity patterns of red fox, Vulpes vulpes, breeding females. Acta Zeveloff,S. I. 1988. Mammalsof the IntermountainWest. Universityof Utah, Theriologica38:427-434. Salt LakeCity, USA. Trewhella,W. J., and S. Harris.1990. Theeffects of railwaylines on urbanfox numbersand dispersalmovements. Journal of Zoology221:321-326. AssociateEditor: Smallwood.

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