8 Potential recolonization and population viability of cougars in the midwest

Friday, August 7, 2009: 10:30 AM
Grand Pavillion III, Hyatt
Michelle A. LaRue , University of Minnesota, Minneapolis, MN
Clayton Nielsen , Zoology, Southern Illinois University Carbondale, Carbondale, IL
Background/Question/Methods

Cougar (Puma concolor) occurrence in the midwestern U.S. has been increasing during the past 20 years.  Since 1990, >150 cougar occurrences in the Midwest have been confirmed by wildlife officials; many cougar confirmations have been of subadult animals, the primary dispersers in cougar populations.  Increased cougar presence in the Midwest is likely being driven by subadult dispersal, which may indicate a recolonization event.  Although wildlife ecologists have acknowledged this potential phenomenon, no research has been conducted to assess timing or spatial dispersion of cougar recolonization or long-term population viability.  We addressed this gap in the literature by modeling potential habitat suitability for cougars, occupancy of potential habitat by cougars via dispersal, and cougar population viability for a 9-state portion of the Midwest.  We first constructed a habitat suitability model for the study region using geospatial data, expert-opinion surveys, and the Analytical Hierarchy Process.  We then identified large, contiguous patches of highly-suitable habitat closest to western populations (i.e., from the Black Hills) most likely to be recolonized by cougars and modeled dispersal to these areas. Using recolonization predictions and habitat-specific demographics derived from published literature, we then used RAMAS/GIS to develop at stage-structured, spatially-explicit population model to analyze population viability.  

Results/Conclusions

Approximately 8% of the 9-state region was considered highly suitable habitat for cougars (>75% suitability). Dispersal of cougars from was modeled from potential western source populations to 6 large, contiguous areas (>2500 km2) of highly suitable habitat and 14 smaller habitat areas close to source populations.  Probability of recolonization of these 20 habitat patches ranged from 10-90% and depended primarily upon patch size, distance from source populations, and dispersal rates of subadult females from source populations.  Population viability of cougars within habitat patches varied considerably based on prey density, road density, and patch size, which affected survival and natality rates.  Our research provides the first assessment of the potential for cougars to become established in the Midwest.  With such information, wildlife ecologists and decision-makers can (1) develop educational and planning tool to address potential human-cougar conflicts, (2) develop assessments of potential top-down effects of cougars on prey populations, and (3) prepare for potential competition between cougars and sympatric carnivores.