West Texas, especially the Trans-Pecos region, mainly consists of desert shrubs and grasslands with patches of higher elevation (1,500 – 2,000 m) mountain ranges. Black bears (Ursus americanus) were extirpated from this area by the 1940s because of predator control and over hunting. In the 1980s, black bears returned to west Texas in a natural recolonization movement from Mexico, where they had survived. The black bear populations of the Trans-Pecos region and northern Mexico fit a mainland-island metapopulation model. Based on previously published research on this recolonization event, I identified several likely habitat recolonization sites and corridor routes for use in predicting possible black bear dispersal throughout the area. Then, using these corridor and recolonization scenarios, I produced a black bear metapopulation model for the Trans-Pecos region.
The possible habitat recolonization site map was created by combining 2 habitat suitability index (HSI) maps and using these HSI maps to define 'core' and 'useable' black bear habitat within the Trans-Pecos region. Using these locations, along with dispersal probabilities and black bear demographic parameters, I created a corridor dispersal map of the area using the program Circuitscape.
The metapopulation model was created using STELLA modeling software. Each recolonization location in the Trans-Pecos region (Big Bend National Park, Black Gap Wildlife Management Area, and the Davis Mountains) has its own black bear subpopulation. The metapopulation model is a stochastic compartment model based on a yearly time step (Δt = 1 yr). This model was tested for the effects of: carrying capacity per site, immigration rates from Mexico, rates of dispersal from Black Gap Wildlife Management Area to the Davis Mountains, and the recovery time for the area after complete extirpation from the Trans-Pecos. This information will help local biologists conserve and manage these returning black bears in the Trans-Pecos region.
|Advisor:||Harveson, Patricia Moody|
|Commitee:||Harveson, Louis A., Warnock, Bonnie J.|
|School:||Sul Ross State University|
|Department:||Agricultural and Natural Resource Sciences|
|School Location:||United States -- Texas|
|Source:||MAI 53/05M(E), Masters Abstracts International|
|Subjects:||Wildlife Conservation, Wildlife Management, Ecology|
|Keywords:||Big Bend National Park, Black Gap Wildlife Management Area, Black bear dispersal and recolonization, Davis Mountains, Metapopulation, Mexico, Texas, Trans-Pecos, Ursus americanus|
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