Small, R.J., Rusch, D.H., Cary, J.R. & Holzwart, J.C. 1997: Population dynamics of ruffed grouse Bonasa umbellus in the fragmented forests of central Wisconsin, USA. - Wildl. Biol. 3: 292.
Survival, reproduction, and dispersal of ruffed grouse Bonasa umbellus in the fragmented forests of central Wisconsin were examined during 1982-1988. Estimates of survival and reproduction indicated the population should have been declining at about 45% per year, yet population densities gradually increased from 5.8 to 7.8 drumming males per 100 ha during the 7-year study. Hunting mortality was highly site-specific, with mortality rates on public lands significantly higher (P < 0.005) than on private lands for both adults (0.73 vs 0.13) and juveniles (0.56 vs 0.09). These results indicate that the regional landscape was comprised of a mosaic of population 'sources' and 'sinks', with population stability maintained through dispersal. Radio-tracking during natal dispersal found that juvenile females moved more than twice the net distance (4.82 vs 2.14 km) at twice the rate (0.53 vs 0.26 km/day) of juvenile males, and distinct sexual differences in habitat selection occurred during autumn. Neither adults nor juveniles were more vulnerable to mortality during transient dispersal than during colonization dispersal. To investigate these regional population dynamics in more detail, a large-scale individually-based metapopulation model was developed which incorporated an active dispersal paradigm based on the observed dispersal dynamics. Then the extinction and recolonization process over 100 years was simulated within each of the 113 individual forest patches in the study landscape. Although preliminary results indicated some agreement with patch-dynamic theory, less intuitive temporal and spatial dynamics of metapopulations may also exist, further emphasizing the critical role of dispersal in metapopulation dynamics, and its complex implications for conservation and management.
Key words: Bonasa umbellus, fragmented forests, metapopulation, population dynamics, ruffed grouse, Wisconsin
Robert J. Small, Colorado Division of Wildlife, 317 West Prospect Road, Fort Collins, Colorado 80526, USA
Donald H. Rusch, National Biological Service, Wisconsin Cooperative Wildlife Research Unit, University of Wisconsin, Madison, Wisconsin 53706, USA
John R. Cary, Department of Wildlife Ecology, 226 Russell Laboratories, University of Wisconsin, Madison, Wisconsin 53706, USA
James C. Holzwart, Wisconsin Department of Natural Resources, P.O Box 343, Berlin, Wisconsin 54923, USA