POPULATION DEMOGRAPHICS AND GENETIC STRUCTURE OF BLACK BEARS IN COASTAL LOUISIANA

The range and abundance of the Louisiana black bear (Ursus americanus luteolus) were greatly diminished during the 20th century. This subspecies was reduced to 3 small, isolated subpopulations in Louisiana as bottomland hardwood habitat was converted to agriculture. These bears were listed as threatened by the U.S. Fish and Wildlife Service in 1992 and a recovery plan was published in 1995. Recovery requires estimates of population parameters to evaluate current population status and future viability. I conducted a mark-recapture study from 2010 to 2012 to estimate demographic parameters of the coastal population of Louisiana black bears. Because inbreeding is a concern for small, isolated populations, I analyzed 23 microsatellite loci to investigate genetic structure and migration rates within the coastal population and between the coastal and other regional populations. Using non-invasive methods, I collected 3,698 hair samples during 3 summers and used DNA to identify 190 individuals. I analyzed encounter histories using Robust Design, a combination of open and closed mark-recapture models, with the full closed captures with heterogeneity model in Program MARK. I estimated density using spatially explicit capture-recapture. I used Akaike’s Information Criterion (AIC) to rank models and averaged across years according to AIC weight. The model-averaged abundance estimate for females was 77 (95% CI = 66–89) and for males was 61 (95% CI = 53–69). Population growth rate was negative from 2010 to 2011, positive from 2011 to 2012, and averaged 1.08. Apparent survival ranged from 0.83 to 0.89 depending on sex and year. Population density was 0.35 bears/km² (95% CI = 0.30–0.41). Principal Coordinate Analysis and assignment tests revealed 2 genetic clusters within the population. Migration rates were male biased and higher than expected based on genetic structure. The population appears to be recovering from past fragmentation but evidence for a bottleneck was inconclusive. I conclude that genetic isolation and inbreeding within the coastal population pose less danger than isolation and demographic threats. My results will ultimately be used as part of a population viability analysis to estimate the sustainability of the Louisiana black bear population.