Patterns of body mass senescence and selective disappearance differ among three species of free-living ungulates

Research on three free-living ungulate populations—bighorn sheep, roe deer, and Soay sheep—reveals distinct patterns of body mass senescence and selective disappearance. The study found that light individuals tended to disappear at both the youngest and oldest ages across all species. Bighorn sheep and roe deer exhibited a continuous decline in body mass that accelerated with age, while Soay sheep experienced a sharp decrease in the two years preceding death. These findings underscore the significance of mass loss in explaining demographic declines in later adulthood and highlight potential differences in senescence processes among related species with similar life histories.

Nussey, D. H., Coulson, T., Delorme, D., Clutton-Brock, T. H., Pemberton, J. M., Festa-Bianchet, M., & Gaillard, J.-M. (2011). Patterns of body mass senescence and selective disappearance differ among three species of free-living ungulates. Ecology, 92(10), 1936–1947. https://doi.org/10.1890/11-0308.1