The acquisition and maintenance of dominance in male and female cooperatively breeding meerkats, Suricata suricatta

Abstract

In group-living species with strong reproductive skew, acquiring a position of dominance is often essential for maximising fitness, and where the frequency of lifetime dominance acquisition is low, substantial variation in fitness among individuals can arise. However, even among dominant individuals there is still substantial variance in fitness attainment, driven by processes such as the maintenance of status, fecundity, and fertility. In this thesis, to understand better the variation in fitness among individuals, I use 26 years of long-term data to investigate the acquisition of dominance and the subsequent maintenance of status and group persistence in a population of cooperatively breeding meerkats, Suricata suricatta, located in the Southern Kalahari. In Chapters 3 and 4, I characterise the distinct routes that subordinates of both sexes pursue to acquire dominance. While there is variation in the frequency that certain dominance routes are used, I find no substantial differences between routes in the traits that determine the acquisition of dominance, the length of tenures or the reproductive success of dominants. In Chapter 5, I distinguish between the reproductive consequences of intrasexual competition from within and outside the group for dominant males. This reveals that while resident immigrant subordinate males compete with the dominant male for reproduction, they also buffer against reproductive competition from outside the group, thereby offsetting their reproductive costs. In Chapter 6, I investigate the factors that influence the maintenance of both sexes’ dominance tenures, while accounting for the distinct causes of tenure loss. I show that heavier dominants are more likely to maintain their position and that dominants of both sexes experience similar levels of within-group intrasexual competition, with increasing numbers of resident competitors increasing the risk of displacement. In addition, dominant males are uniquely vulnerable to extra-group takeovers and resident subordinate males appear to aid in the defence of the group, with higher numbers of subordinate males reducing takeover risk. Furthermore, males are also distinct from female dominants in that a substantial number abandon their dominance, a process that I find is associated with the availability of reproductive opportunities within the group. Finally in Chapter 7, I characterise the processes influencing group persistence, which is important for both the maintenance of a dominant’s tenure and ensuring the persistence of their lineage. I show that groups iii can persist for over a decade and that maintaining a large group size is essential for maximising group longevity. I also find that an endemic form of tuberculosis, Mycobacterium suricattae, plays a considerable role in the failure of groups, being associated with the failure of most long lived groups in the population.