Habitat-Distribution Modeling of a Recolonizing Black Bear, Ursus americanus, Population in the Trans-Pecos Region of Texas

Abstract

Black Bears (Ursus americanus) were once widespread across Texas, but their numbers were reduced in the early 1900s. Recolonization of the Trans-Pecos region of Texas has occurred via bears migrating northward from Mexico. Recent bear sightings have increased in this area. This could be an indication that the population in Texas is beginning to recover, but the population will continue to expand only if there is suitable habitat to occupy. To help identify suitable habitat and restoration areas, we developed a predictive habitat-distribution model by using records of Black Bear sightings from 1996 to 2003 to map the species' distribution. Using Bayesian statistics, we modeled the probability of occurrence of Black Bears in the Trans-Pecos region based on sighting locations. We used GIS layers for land use/landcover, elevation, water sources, and road networks to obtain covariates in our modeling. We used a 10-fold cross-validation to test the effectiveness of using sighting data. Our results indicated a negative association with bare areas, agriculture, and grassland landcovers. In addition, southern aspect, elevation, distance to water, slope, and western aspect also influenced suitable habitat. Both the original and validation datasets correctly classified bear sightings 93.9% and 93.7% of the time, respectively. Our model can be used to target restoration efforts to enhance the ability of the Black Bear to expand in the Trans-Pecos region. It can also identify private landowners most likely to be affected by the expansion of Black Bears for education and cooperative efforts.