Density-dependent intraspecific aggression regulates survival in northern Yellowstone wolves (Canis lupus)
Article first published online: 21 MAY 2014
© 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society
Journal of Animal Ecology
Volume 83, Issue 6, pages 1344–1356, November 2014
How to Cite
Cubaynes, S., MacNulty, D. R., Stahler, D. R., Quimby, K. A., Smith, D. W., Coulson, T. (2014), Density-dependent intraspecific aggression regulates survival in northern Yellowstone wolves (Canis lupus). Journal of Animal Ecology, 83: 1344–1356. doi: 10.1111/1365-2656.12238
- Issue published online: 24 OCT 2014
- Article first published online: 21 MAY 2014
- Accepted manuscript online: 21 APR 2014 06:31AM EST
- Manuscript Accepted: 11 APR 2014
- Manuscript Received: 19 DEC 2013
- National Science Foundation . Grant Numbers: DEB-0613730, DEB-1245373
- Yellowstone National Park
- Yellowstone Park Foundation
- Wellcome grant
- density dependence;
- food availability;
- intraspecific competition;
- population regulation;
- vital rate
- Understanding the population dynamics of top-predators is essential to assess their impact on ecosystems and to guide their management. Key to this understanding is identifying the mechanisms regulating vital rates.
- Determining the influence of density on survival is necessary to understand the extent to which human-caused mortality is compensatory or additive. In wolves (Canis lupus), empirical evidence for density-dependent survival is lacking. Dispersal is considered the principal way in which wolves adjust their numbers to prey supply or compensate for human exploitation. However, studies to date have primarily focused on exploited wolf populations, in which density-dependent mechanisms are likely weak due to artificially low wolf densities.
- Using 13 years of data on 280 collared wolves in Yellowstone National Park, we assessed the effect of wolf density, prey abundance and population structure, as well as winter severity, on age-specific survival in two areas (prey-rich vs. prey-poor) of the national park. We further analysed cause-specific mortality and explored the factors driving intraspecific aggression in the prey-rich northern area of the park.
- Overall, survival rates decreased during the study. In northern Yellowstone, density dependence regulated adult survival through an increase in intraspecific aggression, independent of prey availability. In the interior of the park, adult survival was less variable and density-independent, despite reduced prey availability. There was no effect of prey population structure in northern Yellowstone, or of winter severity in either area. Survival was similar among yearlings and adults, but lower for adults older than 6 years.
- Our results indicate that density-dependent intraspecific aggression is a major driver of adult wolf survival in northern Yellowstone, suggesting intrinsic density-dependent mechanisms have the potential to regulate wolf populations at high ungulate densities. When low prey availability or high removal rates maintain wolves at lower densities, limited inter-pack interactions may prevent density-dependent survival, consistent with our findings in the interior of the park.