Individual contributions to territory defence in a cooperative breeder: weighing up the benefits and costs

Abstract

While investment in territory defence is expected to be influenced by its benefits, the additional role that costs may play is rarely considered. Here, we quantify both benefits and costs of repelling prospecting males in cooperative meerkats, and demonstrate that both are required to explain the substantial variation in individual contributions to the defence observed. Males benefit more from repelling prospectors than females, as males may lose dominance and be expelled during intrusions. Accordingly, males invest the most in repelling prospectors. We also show that males experience an associated cost in the form of reduced weight gain and, as such, heavier males contribute more to chasing prospectors. Finally, we show evidence of a cost not restricted to individuals engaged in chasing: both males and females reduce their contributions to feeding dependent pups when prospectors are present, resulting in a reduction in pup weight gain in this context. Males appear to adjust their contributions to chasing in light of this cost, chasing at lower rates when their group contains dependent young. Our findings support the view that investment in cooperative behaviours can be attributed to benefits and costs, and highlight the additional importance of considering trade-offs in investment between cooperative behaviours.

Early growth, dominance acquisition and lifetime reproductive success in male and female cooperative meerkats

“…; Mares et al. ). Instead, other factors such as immediate condition while dispersing may be more important than competition with siblings for fitness prospects in males (Young et al.…”

The evolutionary interplay of intergroup conflict and altruism in humans: a review of parochial altruism theory and prospects for its extension

“…Analogously, a recent study on meerkats (Suricata suricatta) established that behaviour in defences can be explained via individual cost/benefit analyses to a good extent in this cooperative breeder [31]. Again, those individuals who were likely to suffer the greatest costs in terms of status and reproductive access should have a defence fail, in this case high-ranking reproductive males invested most in group defence.…”

Models of social evolution: can we do better to predict ‘who helps whom to achieve what’?

“…The answer is a qualified yes, in the sense that such models are consistent with helper behaviour that involves resources (usually food) given directly to offspring, which the modeller then chooses to quantify as an increase in their parent's fecundity [104]. Feeding the young also ranks among the most common types of help given in animal societies-though such a statement has to be qualified by a reminder that the diversity of tasks performed is immense, with just a few examples being the 'babysitting' of young meerkats [105]; colony defence in social insects [106,107] with the extreme example of self-sacrificing Forelius pusillus ants sealing off the nest entrance from outside (a suicidal activity as the workers completing the job will die overnight, [108]); participation in territorial boundary disputes [85,109]; and honeybee swarms searching collectively for new nest locations [110]. All of these activities enhance the performance of the colony or group one way or another, but only some of them are directly interpretable as increases in a dominant breeders' fecundity.…”