Development and Application of Habitat Models for Black Bears in Central and Southeast Georgia

Principal Investigator: Dr. Michael J. Conroy, Georgia Cooperative Fish and Wildlife Research Unit, D.B. Warnell School of Forest Resources, University of Georgia, Athens 30602

Graduate Research Assistant: Ms. Kiersten Cook,

ABSTRACT: We will use radiotelemetry data from black bears (Ursus americanus) captured in central Georgia to estimate home ranges and habitat use patterns, with emphasis on adult females. Data will be used to parameterize and validate models for bear habitat use. Validated models will be applied to mapped vegetation data (Georgia GAP) to develop predictions for habitat utilization under alternative scenarios of reintroduction and land use change in southeastern Georgia.

INTRODUCTION

The Ocmulgee River drain and its tributaries supports a unique population of black bears in central Georgia. This population is known to occupy large forested areas in portions of Bibb, Houston, Twiggs, Bleckley, and Pulaski Counties, an area of approximately 300 km². Currently there is a paucity of information for this important species in central Georgia. A preliminary study (Grahl 1985) into the basic ecology of the Ocmulgee drainage bear population was conducted from 1980 to 1985. This study estimated a population density of 3.1 bears per km² (66 bears) on Oaky Woods and Ocmulgee Wildlife Management Areas. This estimate is specific to a "core" area of suitable habitat, and it is likely that densities decrease significantly as distance from large unfragmented forested areas increases.

The proposed study focuses on estimating home ranges and habitat use and preference by black bears in the central Georgia population (CNP), to address two management issues. First, quantification of habitat occupancy is needed in order to assess the long-term viability of CNP. In particular, conservation may need to be directed toward maintenance of critical habitats that are in the process of undergoing rapid conversion (e.g., bottomland types). Second, information about home ranges and habitat use/ preference may be directly applicable to efforts to reestablish black bear populations elsewhere in Georgia. We propose to use data gleaned from this study in conjunction with data and models from Georgia Gap Analysis (Scott et al. 1993) to predict likely distribution patterns of bears for a prospective reintroduction to southeastern Georgia.

STUDY OBJECTIVES

• Estimate home ranges sizes of black bears in central Georgia.
• Estimate habitat use and preference by black bears in the central Georgia population
• Develop and parameterize models for predicting occupancy by bears of habitats in the lower Altamaha drainage
• Use the above habitat models to make recommendations regarding the feasibility of reintroduction of bears to unoccupied habitats in southeast Georgia.

STUDY TASKS AND TIMETABLE

• Study initiation: December 2002
• In cooperation with Georgia DNR personnel, capture and radiomark up to 20 black bears in the study area in Bibb, Houston, Twiggs, Bleckley, and Pulaski Counties. Emphasis will be placed on following adult female bears. April 2003- December 2003.
• Delineate home ranges and habitat use of radiomarked bears. May -December 2003. Where possible radiotrack females to denning sites and determine habitat attributes of these sites.
• Develop habitat models using published data and habitat information from Georgia Gap Analysis. September 2003- April 2004
• Complete thesis and write final report: December 2004

METHODS

Study area

The principal study areas for capture and marking bears will be Ocmulgee and Oaky Woods WMAs in Houston and Twigg Counties. Additional trapping may occur at Bond Swamp NWR. Monitoring will initially focus on these areas but will involve adjacent private lands as necessitated by bear movement; permission will be sought prior to entry on all private lands.

Field Methods

Bears will be captured and immobilized by DNR personnel. UGA personnel will assist with capture as needed and as class scheduling allows. The majority of female bears will be equipped with VHF radio collars having mortality signals. Up to 10 bears, principally juvenile males, will be equipped with retrievable GPS collars. Up to 20 female bears will be selected for intensive radio tracking to determine home range and habitat use patterns. The selected bears will be monitored for an initial period of 2-3 weeks to establish overall diel patterns of activity. Subsequently individuals will be followed according to a rotating schedule to assure that diel patterns of activity are adequately represented across the sample of individuals and to assure independence of observations for subsequent analysis. Depending on the spatial distribution of the marked sample we will endeavor to obtain at least 50 independent observations per individual for computation of home ranges and estimation of habitat use. Locations of VHF transmitters will be estimated via triangulation using truck or hand-held mounted antennas supplemented as necessary by aircraft. Where feasible observers will ascertain the habitat characteristics (forest cover type, topographic features) of the animal's location.

Statistical analysis and modeling

Locational data will be entered into a geographical data base using UTM grid coordinates. Locations will be superimposed over land cover information obtained from Georgia Gap Analysis for descriptive plotting and to associate point locations with land use -land cover information; direct observations of habitat attributes will be added to the database as available.

Home range size will be estimated by minimum convex polygon and kernel methods, taking into account locational error due to triangulation (Samuel and Fuller 1991). Habitat use and preference will be assessed using use-preference statistics (Johnson 1980, Manly 1996) and compositional analyses (Aebischer et al. 1993). Locational data will also be fit to habitat predictors using generalized linear models (SAS 1999). Prediction models will be applied to mapped vegetation data (Georgia GAP) to develop predictions for habitat utilization under alternative scenarios of reintroduction and land use change in southeastern Georgia.

BUDGET

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* ½-time graduate research assistantship for M.S. student

OTHER SUPPORT

• Telemetry equipment (transmitters, receivers, and antennas) purchased by DNR from main project
• DNR biologist and technician lead capture efforts
• Housing provided either at WMA or Bond Swamp NWR (contract to cover utilities from 'travel' above)
• Vehicle (1) provided by Unit; gas and maintenance funded from contract (travel).

LITERATURE CITED

Aebischer, N. J. P. A. Robertson, and R. E. Kenward. 1993. Compositional analysis of habitat use from animal radio-tracking data. Ecology. 74: 1313-1325.

Carlock, D.M., J.C. Ezell, G.D. Balkcom, W.A. Abler, P. Dupree, D.L. Forster. 1999. Black bear management plan for Georgia. Georgia Department of Natural Resources. Semi-Annual Prog. Rep., Atlanta, Georgia, USA 24pp.

Grahl, D.K., Jr. 1985. Preliminary investigation of Ocmulgee River drainage black bear population. Georgia Department of Natural Resources. Final Rep., Fed Aid Proj. W-37-R, Study B-2, Atlanta, Georgia, USA. 15pp.

Johnson, D. H. 1980. The comparison of usage and availability measurement for evaluating resources preference. Ecology. 61: 65-71.

Manly, B. F. J. 1996. Resource selection by animals : statistical design and analysis for field studies. Chapman and Hall, London, New York.

Samuel, M. D. and M. R. Fuller. 1994. Wildlife radiotelemetry. Pp. 370-418 in. T. A. Bookhout, e.d. Research and management techniques for wildlife and habitats. Fifth ed. The Wildlife Society, Bethesda, Maryland, USA.

SAS INSTITUTE, INC. 1993. SAS^® Technical Report P-243, SAS/STAT^® Software: The GENMOD Procedure, Release 6.09. Cary, North Carolina, USA..