North Carolina State Researchers are conducting a project on Bull Neck Swamp to determine homerange, movement patterns, and dispersal of bobcat (Lynx rufus) using satellite collars.
The objectives of this research are to:
1. Determine the most efficient survey technique that can be used in wetland habitats of North Carolina for estimating abundances and distributions of mammals.
2. Develop a model of habitat use by bobcats in Eastern N.C. wetlands.
3. Using GPS collars, determine seasonal use by bobcats of areas with different landcovers in a wetland.
4. Using data from bobcats at BNS, test my model and other pre-existing, landscape level models.
5. Develop a global database of bobcat tracks that will aid in non-invasive survey techniques used to estimate populations through the cooperation of Wildtrack (wildtrack.org).
Objective 1: As land managers it is important to have a thorough understanding of species diversity, species richness, population size, and habitat use of all species occupying BNS. A study was completed by Hutchens (2007) that provided detailed information on herpetofauna species richness and habitat use. Although this study provided important management information for BNS, data on mammal diversity, abundance, and habitat use is lacking.
By conducting survey techniques for mammals at BNS we can develop population abundance and distribution indices and determine the most efficient technique that may be effective in Eastern N.C. wetlands. Mammal survey techniques implemented on BNS include spotlight, scent station and camera monitoring, predator calling, hair sampling and fecal line transects.
An example of one months results for tracks located at scent stations are shown here and include black bear (Ursus americanus), bobcat (Lynx rufus), gray fox (Urocyon cinereoargenteus), American beaver (Castor canadensis), muskrat (Ondatra zibethicus), common raccoon (Procyon lotor), and virginia opossum (Didelphis virginiana). Preliminary field work conducted in the summer of 2007 estimated at least 6 individual bobcats on the track through photo identification. In March 2008, bobcats were trapped and radio-collared to monitor habitat use and movement.
Signs of coyote (Canis latrans ) are rare on the track. Objective 2: Habitat-relation models may be useful to monitor indicator species and their habitats. Habitat Suitability Index (HSI) models have been used since the early 1980's and were initially developed by the U.S. Fish and Wildlife Service based on expert opinion, empirical data, or both. The HSI for bobcat was developed in 1987 for application in the Southeastern United States (Boyle and Fendley 1987). Understanding specific habitat requirements at BNS are essential to planning land management activities on bobcat population size adn distributions.
Over 200 vegetation surveys were conducted in Summer 2008 throughout BNS. Measurements taken include; ground cover, visual obstruction, canopy cover, basal area, low shrub species and abundance, nearest tree/species and temperature. Supervised classification on high resolution aerial photography along with more extensive ground truthing will be conducted to determine habitat variation at BNS.
Objective 3: Landcover use by bobcat has been studied in a few areas of the United States but varies by region and by sampling technique used (click here for details). Currently, bobcat landcover use and selection at BNS is unknown. Based on work of Lancia et al. (1982) and King et al. (1983), variation in landcover use and techniques presented in the peer reviewed literature, and on pilot research, we hypothesize that in the fragmented landscape of BNS bobcat will select early successional and upland landcovers. In March 2008, 6 bobcats were trapped and GPS collared with the help of USDA Aphis. Preliminary results show use of much of the habitat at BNS.
Objective 5: Wildtrack is an organization that specializes in non-invasive population monitoring techniques. Wildtracks' protocol derives an algorithm by using images of 20 left hind tracks from 20 individuals (in our case 20 bobcats, below left image). Digital photographs are taken from known bobcats of prints noting the species, date, location, and track number. The images are uploaded into a software program where landmark points are placed on reference points on the footprint (below right image). Measurements are taken of distances and angles between these points. A resulting geometrical profile is analyzed using JMP software making it possible to identify individual animals. Wildtrack has successfully applied this technique to white rhino (Ceratotherium simum) and the Bengal tiger (Panthera tigris) and is in the process of building databases for black rhino (Diceros bicornis), the Iberian lynx (Lynx pardinus), polar bear (Ursus maritimus), and bobcat.
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