Project
Effects of stochastic intensive predation episodes on reproductive and actuarial senescence in bighorn sheep (Ovis canadensis)Stochastic intensive predation episodes by specialist individuals have been observed in several wild species, including bighorn sheep (Ovis canadensis). These episodes impact population dynamics through direct (e.g. lowered survival of lambs and females) and indirect effects. Intense predation by cougar (Puma concolor) has been found to lower mass gain in ewes and lambs and to affect negatively reproductive success in ewes born during cougar years. These episodes hit species organised in small isolated populations, such as alpine ungulates, especially hard. Their effects surpass those of density-dependent or environmental factors and can generate an Allee effect in impacted populations. They could potentially lead to extinction in some populations, thus affecting the stability of the species. In addition, several studies have shown a link between conditions during development and actuarial and reproductive senescence. Favourable environmental conditions in early life are associated with a slower senescence rate in many species. My goal is to evaluate the long term effects of stochastic intensive predation episodes on bighorn sheep population dynamics by checking if these episodes influence actuarial and reproductive senescence for individuals born in impacted years. I will use data from the longitudinal individual based study taking place in Ram Mountain, Alberta, since 1971. The Ram population had four intensive cougar predation episodes totalling nine years. I will evaluate if the reproductive and actuarial senescence rate is superior for cohorts born during cougar years compared to those born during low predation years.
