Female reproductive success and costs in an alpine capital breeder under contrasting environments

Abstract

In large mammals, female reproduction is highly dependent on female body condition and thus on environmental conditions. We studied female reproductive success in two contrasting populations of Alpine Ibex: one colonizing, experiencing no density-dependence, and for which environmental conditions are consequently not limiting, the other well established, experiencing density-dependence and thus living in a limiting environment. Female body condition was better in the colonizing population than in the well-established one. As a result, reproductive success was higher in the colonizing population (80% of females reproduced each year) than in the well-established one (only 45% of females reproduced each year). We did not detect any cost of reproduction on subsequent reproduction in either of the populations, suggesting that ibex females adopt an extremely conservative reproductive tactic by limiting their reproductive effort when resource availability is reduced. However, we found a higher variance of individual reproductive success in the well-established population than in the colonizing one. Such a contrast can be accounted for by the between-site differences in body condition (i.e., a poor general body condition in the well-established population versus a good general condition in the colonizing one).