Bobcat Survey of Portage County

Introduction

While the presence of the bobcat is well documented in the northern third of Wisconsin through harvest data and snow tracking records, their distribution south of State Highway 64 is unknown (Rolley et al., 2001).  In order to properly manage a species, it is imperative to understand their distribution.  Portage County (Fig. 1) is located at the southern edge of the bobcats known distribution in the state of Wisconsin, and therefore is an ideal location to initiate a study that will further the examine the presence of bobcat in Wisconsin.

Figure 1. Map of Wisconsin depicting the bobcat management zone (created by Leslie Adams)

The presence of a species can be documented through various methods including questionnaires, sighting reports, and presence of sign.  The presence of sign is often the preferred method as it minimizes the ambiguity that may be associated with questionnaires and sighting reports.  Bobcat sign can include scats, tracks, scratches or hair.  Hair can be used to identify species by analyzing hair length, banding patterns, and cuticle patterns. We designed a study that used non-invasive hair snares in an attempt to collect bobcat hair to document their presence in Portage County.
 

Methods and Study Area

To identify potential bobcat habitat in Portage County,  we created maps of land cover and wetland habitat types.  Land cover data was derived  from Landsat TM satellite imagery (WISCLAND), wetland data was derived from Wisconsin Wetland Inventory (WWI), and maps were created in ArcMap 9.1 (Environmental Systems Research Institute, Redlands, California, USA).

Bobcats select for lowland deciduous and coniferous wetlands (Lovallo and Anderson 1996).  Areas identified with potential bobcat habitat included land managed by the Wisconsin Department of Natural Resources (WDNR) including the Mead Wildlife Area, Dewey Marsh Wildlife Area, Little Wolf River Fishery Area, Bradley Creek Fishery Area, Flume Creek,  and Richard J. Hemp Fishery Area (Poncho Creek). Wildlife managers from the WDNR were contacted to obtain permission to erect snares and were solicited for suggestions on the placement of snares within WDNR lands.  We identified private lands along the Plover River, Lost Creek, and the Wisconsin River with suitable bobcat habitat; permission was obtained from landowners to erect snares on their land.  A map was created for each private property that delineated lowland and coniferous wetland habitat types (Fig. 2).

Snare were constructed by first cutting landscape edging into 1 m pieces (Fig. 3).  10cm x 10cm cloth swatches were stapled to one end of the edging (Fig. 4). Glue, heated in an oven at 425 degrees and then kept on a hot plate, was spread on the end of the snare, opposite to the cloth (Fig. 5).

Figure 3. Austin and Kyle cutting the edging (photo by Larissa Condon)

Figure 5. Left: Joe Welch removing the glue from the oven. Right: Kyle, Austin and Joe spreading glue on the snares (photo by Larissa Condon).

We constructed visual attractants by fastening 15-20cm strips of mylar fire blankets (Fig. 6) to coat hangers.

Figure 7. Leslie fastens a snare to a tree on private property (photo by Mitchell Jones)

We erected 65 hair snares in late February and early March of 2007. Snares were fastened with standard nails or screws on trees that had their lower branches removed (Fig. 7).  Felids prefer to scent-rub in the cranial body areas (Reiger 1979), therefore snares were erected with the glue 0.5m above the ground to facilitate this behavior.   We baited hair snares by spreading 0.3 oz of an olfactory attractant, Powder River Cat Call, on the cloth swatches located on the inside of the snare (Fig. 8). We hung the mylar attractants on a tree branch within 2 m of the snare to visually attract bobcat.  We checked and removed hair snares between 2 and 3 weeks after deployment (Figs. 9).

Figure 8. Baiting the snare with a scent lure (photo by Mitchell Jones).

Figure 9. Larrisa checks hair snares on private property (photo by Mitchell Jones)

Hairs were removed with tweezers and stored in sealed envelopes.  Hairs were identified as bobcat based on physical characteristics and microscopic analysis of internal structures (Moore et al. 1974).  Hairs were measured and banding patterns examined. To analyze the hair cuticle, we created an imprint by pressing the hair into semi-dry clear nail polish that was painted on a microscope slide.

 

Figure 11. Map of hair snares in Portage Co., Wisconsin (created by Leslie Adams).

Results

We collected hair samples from several snares, however only one snare, located in northeastern Portage county, yielded hairs that were positively identified as bobcat hair (Fig. 11).  Non-bobcat hairs found on other snares were not identified to species. 

Discussion

The capture rate for non-invasive hair snares is dependent on several factors: the type of snare (glue vs. wire), placement of the snare at the landscape and local level,  and the efficacy of the scent and visual lures.  One hypothesis explaining our low capture rate is the type of glue used.  It has been found in other studies that glue that has been spread onto the snare in a clumpy fashion has been more successful at capturing hairs than glue that was spread on very smoothly (Joe Welch, personal communication).  Also, although we were able to select potential bobcat habitat on the landscape scale with the aid of geographic information systems (GIS), we were limited by experience in the placement of snares at the local scale.  In addition, while Powder River Cat Call was found to elicit a significantly higher rate of bunting (rubbing) in cougars (Joe Welch, personal communication), its effectiveness with bobcats has not been measured.  

We hypothesize that bobcats are distributed throughout Portage County to an extant that was not reflected in the capture rate of hairs.  While one of the snares that was located on private property did not capture any hair, the landowners recorded the sounds of a bobcat from their back porch during one evening of the survey (Eric Anderson, personal communication).

Literature Cited

Fuller, T. K., W. E. Berg, and D. W. Kuehn. 1985. Bobcat home range size and daytime  cover-type use in north-central Minnesota.  Journal of Mammalogy 66:568-571.

Lovallo, M. J., and E. M. Anderson. 1996. Bobcat (Lynx rufus) home range size and habitat use in northwest Wisconsin. American Midland Naturalist 135:241-252.

Moore, T. D., E. S. Liter, and C. E. Dugnolle. 1974. Identification of the dorsal guard hairs of some mammals of Wyoming. Wyoming Department of Game and Fish, Cheyenne, USA

Reiger, I. 1979. Scent rubbing in carnivores.  Carnivores 2:17-25.

Rolley, R. E., B. E. Kohn, and J. F. Olson. 2001. Evolution of Wisconsin's bobcat harvest management program. Pages 61-66 in A.Woolf, C. K. Nielsen, and R. D Bluett, editors. Proceedings of a symposium on current bobcat research and implications for management. The Wildlife Society 2000 Conference, Nashville, Tennessee, USA.