Masters Theses

Date of Award

8-2002

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

Joseph D. Clark

Committee Members

David A. Etnier, Michael R. Pelton, Frank T. van Manen

Abstract

Black bears (Ursus americanus floridanus) once were abundant throughout Alabama (Hall 1981), but today sightings of bears are common only in the extreme southwestern portion of the state. The objectives of my study were to determine the distribution of black bears in southwestern Alabama, estimate basic demographic parameters, and evaluate their habitat needs. To determine bear distribution I established and monitored 168 bait stations within the study area from 1998 to 2000. Baits were checked for bear activity at approximately weekly intervals. In areas where bear presence was detected I trapped from 22 October--20 November 1998, 22 June--4 November 1999, and 24 May--29 October 2000, using Aldrich spring-activated foot snares. I recorded 23 captures of 17 (10F: 7M) individual bears from 53 trap sites. I radiocollared 16 (10F: 6M) individual bears and monitored movements once every 10 days in 1999 and twice every 7 days in 2000 by fixed-wing aircraft. Sizes of average home range using the 95% minimum convex polygon technique were 7.8 km2 for females (n = 10) and 67.1 km2 for males (n = 6). Home range overlap was extensive between and within sexes. I estimated second-order habitat selection (Johnson 1980) for bears in southwest Alabama using compositional analysis (Aebischer et al. 1993). I generated 2 available habitat areas for the analysis, one including the Mobile-Tensaw Delta, and the other excluding the delta. The analysis extent including the delta suggested that bears were more likely to position their home ranges in areas that contained pine, and the analysis extent excluding the delta suggested that bears were more likely to position their home ranges in areas that contained woody wetlands.

Among 16 radiocollared bears, 4 lost their collars (3 summer 2000, 1 winter 2001) and one bear died in fall 2000. Cumulative annual survival over the duration of the study was 0.957 (95% CI = 0.880-1.0). I used a population model (RISKMAN version 1.5.413; Ontario Ministry of Natural Resources, Toronto, Ontario, Canada) to estimate population growth and probability of extinction. With the given parameter estimates for the population growth simulation, and an estimated initial population of 30 individuals, the mean annual growth rate (λ) was 1.027. Additionally, I estimated extinction probability for initial populations of 20, 30, and 40 individuals. Extinction occurred in 17, 13, and 4% of the trials, respectively. This variation in extinction probability suggests that the loss or gain of only a few individuals could greatly affect the stability and perpetuity of the population. I used 19 hair samples from 17 live captured and 2 vehicle-killed bears to determine the total observed alleles and frequencies and over all measure of heterozygosity for the samples collected. Average number of alleles per locus was 2.88 (range 2-4) and average heterozygosity for the 8 loci sampled was 31.6% (range 5-58%). These numbers were low compared to similar analysis for other southeastern black bear populations; this was likely due to the low amount of genetic interchange with other bear populations and the low number of breeding individuals in the population.

The bear population in southwest Alabama is being maintained in only a few small isolated areas where breeding females occur, and thus may be one of the most threatened populations of black bears in North America. These breeding females appear to be associated with feeder streams and associated swamps and bays not subject to river flooding adjacent to pine and oak-pine upland habitats. Bears appear to be scarce in the extensive seasonally flooded habitats along the Mobile, Tensaw, Alabama, and Tombigbee rivers; this is likely due to the low number of sufficient den trees, and isolation from current populations. However, because of its extensive size (app. 100 km2) and natural isolation, these seasonally flooded wetlands may hold the greatest potential for bear habitat in the region.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS