Genetic implications of reduced survival of male red deer Cervus elaphus under harvest
Jeffrey J. Hard, L. Scott Mills & James M. Peek
Hard, J.J., Mills, L.S. & Peek, J.M. 2006: Genetic implications of reduced survival of male red deer Cervus elaphus under harvest. - Wildl. Biol. 12: 427-441.
We use simple, multivariate evolutionary models to evaluate the short-term potential for size-selective harvest to reduce genetic variability and alter life history in cervids. These genetic effects limit sustainable levels of harvest of the animals because they determine how changes in sex ratio, generation length and traits contributing to fitness influence population growth rate and local adaptation. Our analysis of harvest-mediated adaptive evolution employs a genetic approach that parameterizes models with empirical data obtained from European red deer Cervus elaphus. The analysis indicates that harvest, if sufficiently high to reduce the breeding ratio of males to females to below about 15:100, can reduce effective population size to a level that threatens adaptive potential. The reduction in effective size is realized through decreases in both sex ratio of breeders and the age of breeding males. Predicted selective effects of harvest on body size indicates a weak potential to alter most life-history traits over 10 generations under two harvest scenarios; the patterns suggest that current modes of harvest are unlikely to produce substantial life-history changes in red deer over 10 or fewer generations unless the genetic influences on red deer traits are considerably higher than those predicted here. Nevertheless, male reproductive success is expected to decline detectably if male harvest rate is sufficiently high (> 30%). Collectively, our results imply that harvest methods should permit higher posthunt male:female ratios (18:100 or higher) and ensure that a sufficient number of larger, older males survive the breeding season. The capacity of selective harvest to alter demography and life history depends heavily on the genetic covariance structure underlying variation in these traits, information that is unknown for many red deer populations. Prudent harvest management should therefore implement and monitor approaches to hunting that aim to conserve life-history variation; meanwhile, use of less selective methods can reduce the risk to long-term adaptive potential and may permit higher sustainable harvest rates.
Key words: Cervus elaphus, effective population size, elk, fitness, harvest, quantitative genetics
Jeffrey J. Hard, Conservation Biology Division, NOAA/NMFS Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, Washington, 98112, USA - e-mail: jeff.hard@noaa.gov L. Scott Mills, Wildlife Biology Program, University of Montana, Missoula, Montana, 59812, USA - e-mail: smills@forestry.umt.edu James M. Peek, Department of Fish & Wildlife Resources, University of Idaho, Moscow, Idaho, 83844, USA - e-mail: peek@uidaho.edu
Corresponding author: Jeffrey J. Hard
Received 30 April 2005, accepted 20 October 2005
Associate Editor: Atle Mysterud