Author Institution:  National Park Service, Pictured Rocks Science CenterAuthor Institution:  School of Forest Resources & Environmental Sciences, Michigan Technological UniversityWe compared the efficacy of Victor® Tin Cat® and Sherman live traps for capturing small mammals in northern hardwood and red pine (Pinus resinosa) stands in the north-central Upper Peninsula of Michigan during 2001. Overall mean capture rates (total captures/100 adjusted trap nights) by habitat were greater (P <0.030) for Sherman traps than for Tin Cat traps. Capture rates remained lower for Tin Cat traps in northern hardwood (P = 0.004) but not red pine (P = 0.936) habitat after adjusting for species (sciurids) unable to enter them. Greater species diversity values were obtained using Sherman traps in both habitats. We conclude that in sampling arrays tested, Victor Tin Cat traps were less effective than Sherman traps for estimating small mammal abundance and diversity

Belant, Jerrold L.

Windels, Steve K.

The Ohio Journal of Science

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16 VOL.  107COMPARING SMALL MAMMAL LIVE TRAPSEfficacy of a Multiple-Capture Live Trap for Small Mammals1JERROLD L. BELANT AND STEVE K. WINDELS2, National Park Service, Pictured Rocks Science Center, N8391 Sand Point Road, Munising,MI 49862; School of Forest Resources and Environmental Science, Michigan Technological University, 1400 Townsend Drive, Houghton,MI 49931ABSTRACT.  We compared the efficacy of Victor® Tin Cat® and Sherman live traps for capturing small mammals in northernhardwood and red pine (Pinus resinosa) stands in the north-central Upper Peninsula of Michigan during 2001. Overallmean capture rates (total captures/100 adjusted trap nights) by habitat were greater (P <0.030) for Sherman traps than for TinCat traps. Capture rates remained lower for Tin Cat traps in northern hardwood (P = 0.004) but not red pine (P = 0.936)habitat after adjusting for species (sciurids) unable to enter them. Greater species diversity values were obtained using Shermantraps in both habitats. We conclude that in sampling arrays tested, Victor Tin Cat traps were less effective than Sherman trapsfor estimating small mammal abundance and diversity.OHIO J SCI 107 (2):16-18, 20071Manuscript received 15 May 2005 and in revised form 29 October 2006(#05-22).2Present address: National Park Service, Voyageurs National Park, 3131Highway 53 South, International Falls, MN 56649INTRODUCTIONLive traps are commonly used to estimate small mammalabundance and diversity (for example, Von Trebra and others1998; Carey and Wilson 2001). Differential trapping successamong types and sizes of small mammal live traps has beendemonstrated (Slade and others 1993; O’Farrell and others 1994).Consequently, interpretation of results for a particular trap typecan only be made with some knowledge of the trap’s perform-ance relative to other trap types.Multiple-capture live traps have been used in several recentstudies of small mammal ecology and distribution, with the com-mercial Victor Tin Cat trap (Woodstream Corp., Lititz, PA) usedmost commonly (for example, Bowman and others 2001a,b,c).One proposed benefit of using these traps is a reduction in thenumber of traps necessary to sample an area due to their multiple-capture capability. Tin Cat traps reset after each capture andcan hold several small mammals simultaneously. The websitefor the manufacturer of the Tin Cat trap (www.woodstream.com)states these traps can hold up to 30 mice. Studies by Bowmanand others (2001a,b,c) used arrays of five Tin Cats in a crosspattern spaced 35 m apart, which presumably sampled the samearea as 25 Sherman traps set in a 5 x 5 grid with 10 m spacing, or acircle of about 50 m radius (J. Bowman, Ontario Ministry ofNatural Resources, personal communication).Another potential benefit of Tin Cat traps is the increasedlikelihood of multiple captures due to the presence of a smallmammal in the trap. An animal in the trap may help otherindividuals overcome a neophobic response. Residual odors ofconspecifics in traps has enhanced capture efficacy for severalsmall mammals species (Rowe 1970; Drickamer 1984; Tobin andothers 1994).Despite its increasing use in ecological studies, the efficacy ofthe Victor Tin Cat has not been thoroughly tested against themore commonly used Sherman live trap (H. B. Sherman TrapsInc., Tallahassee, FL). Our objective was to compare small mam-mal capture rates and species composition between Victor TinCat and Sherman live traps in previously used trap arrays todetermine the effectiveness of Tin Cat traps in estimatingabundance and diversity of small mammals.MATERIALS AND METHODSThe study was conducted in the north-central Upper Pen-insula of Michigan, on lands administered by Pictured RocksNational Lakeshore and Hiawatha National Forest. Trappingwas conducted in two habitats: northern hardwoods with a dom-inant overstory of sugar maple (Acer saccharum) and Americanbeech (Fagus grandifolia), and a red pine (Pinus resinosa)plantation.We used collapsible Sherman live traps (Model LFG) de-signed for single captures (Fig. 1). Sherman traps were 8.0 x8.8 x 23.4 cm with one tapered 6.5 to 7.0 x 8.0 cm entrance.Victor® Tin Cat® live traps (Model 308) were 26.7 x 15.9 x 4.8 cmwith a clear plastic lid and two 2.8 x 3.5-cm entrances. TinCat traps were designed for multiple captures.The experimental design in each habitat was a randomizedsplit-block with 6 replicates. Each block consisted of 25 Shermantraps and 5 Tin Cat traps. We placed Sherman traps in a 5 x 5 gridwith 17.5-m spacing for an effective trapping area of about7,650 m2. We placed a Tin Cat trap in the center of each splitand remaining traps 35 m from center in the cardinal directions;this array was designed to sample a 50-m radius around the centertrap (effective trapping area of 7,850 m2; Bowman and others2001a,b,c). Blocks and splits within blocks were separated by >25m; blocks were >25 m from habitat edge. All traps were placed in“most likely runway” positions, baited with rolled oats and peanutbutter, and rebaited as necessary. Prebaiting was not conducted.Cotton was placed in traps to provide bedding. Traps were setinitially during morning and checked 3 times each day for 4 days,resulting in 100 and 20 unadjusted trap nights/block for Shermanand Tin Cat traps, respectively. Individuals captured were identi-fied to species and released at their respective capture sites. Wefollowed animal care and use guidelines outlined by the AmericanSociety of Mammalogists (1987).To standardize trapping effort, Sherman traps that weresprung were adjusted using 0.5 time intervals (that is, trapnights; Belant 1992; Beauvais and Buskirk 1999). Tin Cat trapsallowed multiple captures and were not adjusted for unlessdisturbed or missing. We calculated mean number of captures/100 adjusted trap nights for each trap type in both habitats. Wealso calculated mean capture rates excluding sciurids (red squirrel[Tamiasciurus hudsonicus], eastern chipmunk [T. striatus], andleast chipmunk [Eutamius sciurus]), as these species were toolarge to enter Tin Cat traps.OHIO JOURNAL OF SCIENCE 17J. L. BELANT AND S. K. WINDELSFIGURE 1.  Victor® Tin Cat® (top) and Sherman (bottom) live traps used in efficacytrials, Upper Peninsula of Michigan, July 2001.Because of unequal variances, we used Wilcoxon rank sumtests (Zar 1984) to compare mean rank scores of capture ratesbetween trap types in each habitat using PROC NPAR1WAY(SAS Institute Inc. 1990). Means are reported with +1.0 standarderror; statistical significance was established at P <0.050.We used Species Richness, Shannon-Weiner, and Simpson’sindices to compare species diversity of small mammals capturedwith each trap type in each habitat (Colinvaux 1986; Kirkland1990). Species Richness (S) is a measure of the number of speciesdocumented by capture. The Shannon-Weiner index (H')measures the probability of selecting the identity of an indi-vidual taken from the sample at random using the equation:H' = -Σ pi ln piWhere pi is the proportion of the total number of indi-viduals in the ith species for i = 1 to n.; H' increases withspecies diversity. Simpson’s index (l) is the probability that anytwo individuals selected at random will be the same species anduses the equation:λ = Σ pi2for i = 1 to n. Simpson’s index is an inverse measure of diversityin that species diversity increases as λ decreases.RESULTSWe captured 253 individuals in 1,440 unadjusted trap nights,141 in northern hardwood and 112 in red pine. In the northernhardwood habitat, 139 were captured in Sherman traps and 2were captured in Tin Cat traps. We captured 112 individuals inSherman traps and 9 in Tin Cat traps in the red pine stand.Deer mice (Peromyscus maniculatus) and eastern chipmunks werethe species most commonly captured in both habitats (Fig. 2).FIGURE 2.  Small mammals captured using Sherman and Victor® Tin Cat® live trapsin northern hardwood (top) and red pine stands (bottom), north-central UpperPeninsula of Michigan, July 2001.Overall mean capture rates were greater for Sherman trapsthan for Tin Cat traps in northern hardwood (Z = 2.87, P =0.004) and red pine habitats (Z = 2.16, P = 0.030; Table 1).After adjusting for sciurid captures, capture rates remained higherfor Sherman traps in northern hardwoods (Z = 2.85 P = 0.004)but not in the red pine habitat (Z = 0.80, P = 0.936).We captured 7 species overall, 3 in northern hardwood and 7in red pine. In the northern hardwood habitat, 3 species werecaptured in Sherman traps and 1 species was captured using TinCat traps. We captured 7 species in Sherman traps and 2 speciesin Tin Cat traps in the red pine stand. Greater species diversityvalues were obtained using all 3 indices from Sherman traps in18 VOL.  107COMPARING SMALL MAMMAL LIVE TRAPSTABLE 1Small mammal capture rates (individuals/100 adjusted trap nights)using Sherman and Victor Tin Cat live traps, north-centralUpper Peninsula of Michigan, July 2001.ShermanWith sciurids Without sciurids Tin CatsHabitat x SE x SE x SENorthernhardwood 8.1 2.7 4.7 0.4 0.9 0.6Red pine 6.0 0.9 2.8 0.8 2.5 0.9both habitats (Table 2).One multiple capture (2 deer mice) was recorded for Tin Cattraps; only individual captures were recorded for Sherman traps.DISCUSSIONOverall capture rates and species diversity were lower withTin Cat than with Sherman traps. Only 4% of total individualsand one-half of non-sciurid species were captured using Tin Cattraps. Although capture rates were similar between trap types inred pine habitat, few individuals were captured in Tin Cat traps.Thus, small differences in the number of individuals or speciescaptured using Tin Cat traps could have a large effect on estimatesof abundance and species diversity. Further, the small openingsize of Tin Cat traps does not allow for capture of sciuridswhich are frequently important for assessing small mammalcommunity abundance and diversity.Olfaction is important in the social biology of small mammals(Stoddart 1974) and residual odors from small mammals in trapshave been reported to enhance trapping efficacy (Drickamer 1984;Tobin and others 1994). The potential benefit of the presenceof small mammals in Tin Cat traps as attractants to enhancecapture rates through multiple captures was not observed in thisstudy. Residual odor of small mammals captured was present inboth trap types. Therefore, visual and olfactory cues were notadvantages for using Tin Cat traps in our study.Small mammal capture rates and trap efficacy vary markedlyacross studies. Location, season, and trap type, among other factors,TABLE 2Small mammal species diversity using Species Richness (S),Shannon-Weiner (H'), and Simpson’s (λ) indices calculatedfrom captures using Sherman and Victor Tin Cat live traps,north-central Upper Peninsula of Michigan, July 2001.ShermanWith sciurids Without sciurids Tin CatHabitat S H' λ S H' λ S H' λNorthernhardwood 3 0.79 0.40 2 0.54 0.65 1 0 1.00Red pine 7 1.54 0.27 4 0.84 0.55 2 0.61 0.56influence capture rates (Wiener and Smith 1972; Williams andBraun 1983; Mengak and Guynn 1987). Indeed, multiple studiescomparing identical trap types have reached different conclusionson capture effectiveness (Sealander and James 1958; Wiener andSmith 1972). Tin Cat and Sherman live traps have reportedly hadsimilar capture rates in a previous study (J. Bowman, OntarioMinistry of Natural Resources, personal communication). In traparrays and habitats we compared, however, we do not recommendTin Cat over Sherman live traps. While three days of prebaitingprior to trapping was used previously (Bowman and others2001a,b,c), we do not believe that prebaiting in our study wouldhave changed the relative efficacy of the trap types. Althoughequipment costs and trapping effort were greater with Shermantraps, greater numbers of individuals and species captured usingSherman traps will likely result in improved estimates of smallmammal abundance and diversity.ACKNOWLEDGMENTS.  We thank J. Bowman for critical review of this manuscript. A.Kavalunas, N. Z. Lapinski, R. Posey, and K. A. Stanley assisted with fieldwork. K.Doran (Hiawatha National Forest) provided access to study sites. Funding was providedby the National Park Service Pictured Rocks Science Center, Michigan TechnologicalUniversity, and the Michigan Department of Natural Resources Natural Heritage Fund.LITERATURE CITEDAmerican Society of Mammalogists.  1987.  Guidelines for the Capture, Handling,and Care of Mammals. Lawrence (KS): Amer Soc of Mammalogists. 47 p.Beauvais GP, Buskirk SW.  1999.  Modifying estimates of sampling effort toaccount for sprung traps. Wildl Soc Bull 27:39-43.Belant JL.  1992.  Efficacy of three types of live traps for capturing weasels,Mustela spp. Can Field-Natural 106:394-7.Bowman J, Forbes G, Dilworth T.  2001a.  Landscape context and small-mammal abundance in a managed forest. For Ecol Manage 140:249-55.Bowman J, Forbes G, Dilworth T.  2001b.  The spatial component of variation insmall-mammal abundance measured at three scales. Can J Zool 79:137-44.Bowman J, Forbes G, Dilworth T.  2001c.  Spatial and temporal patterns of anirrupting population of deer mice. J Mammal 82:567-72.Carey AB, Wilson SM.  2001.  Induced spatial heterogeneity in forest canopies:responses of small mammals. J Wildl Manage 65:1014-27.Colinvaux PA.  1986.  Ecology. New York: John Wiley. 725 p.Drickamer LC.  1984.  Capture of two species of Peromyscus at live traps baitedwith male and female odors. J Mammal 65:699-702.Kirkland GL Jr.  1990.  Patterns of initial small mammal community changeafter clearcutting of temperate North American forests. Oikos 59:313-20.Mengak MT, Guynn DC Jr.  1987.  Pitfalls and snap traps for sampling smallmammals and herpetofauna. Am Midl Natural 118:284-8.O’Farrell MJ, Clark WA, Emerson FH, Jaurez SM, Kay FR, O’Farrell TM,Goodlett TY.  1994.  Use of a mesh live trap for small mammals: are resultsfrom Sherman live traps deceptive? J Mammal 75:692-9.Rowe FP.  1970.  The response of wild house mice (Mus musculus) to live-trapsmarked by their own and by a foreign mouse odour. J Zool (London)162:517-20.SAS Institute Inc.  1990.  SAS/STAT User’s Guide. Release 6.03. Cary (NC):SAS Institute Inc. 1686 p.Sealander JA, James D.  1958.  Relative efficiency of different small mammaltraps. J Mammal 39:215-23.Slade NA, Eifler MA, Gruenhagen NM, Davelos AL.  1993.  Differential effective-ness of standard and long Sherman livetraps in capturing small mammals.J Mammal 74:156-61.Stoddart DM.  1974.  The role of odor in the social biology of small mammals. In:Birch MC, editor. Pheromones. Amsterdam (Netherlands): North HollandPubl. p 297-315.Tobin ME, Sugihara RT, Engeman RM.  1994.  Effects of initial rat captures onsubsequent capture success of traps. Proceedings of the Vertebrate PestConf. 16:101-5.Von Trebra C, Lavender DP, Sullivan TP.  1998.  Relations of small mammalpopulation to even-aged shelterwood systems in sub-boreal spruce forest.J Wildl Manage 62:630-42.Wiener JG, Smith MH.  1972.  Relative efficiencies of four small mammal traps.J Mammal 53:868-73.Williams DF, Braun SE.  1983.  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Efficacy of a Multiple-Capture Live Trap for Small Mammals

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Efficacy of a Multiple-Capture Live Trap for Small Mammals

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