Abstract
In many species, particular individuals consistently lead group travel. While benefits to followers often are relatively obvious, including access to resources, benefits to leaders are often less obvious. This is especially true for species that feed on patchy mobile resources where all group members may locate prey simultaneously and food intake likely decreases with increasing group size. Leaders in highly complex habitats, however, could provide access to foraging resources for less informed relatives, thereby gaining indirect benefits by helping kin. Recently, leadership has been documented in a population of bottlenose dolphins (Tursiops truncatus) where direct benefits to leaders appear unlikely. To test whether leaders could benefit indirectly we examined relatedness between leader-follower pairs and compared these levels to pairs who associated but did not have leader-follower relationship (neither ever led the other). We found the average relatedness value for leader-follower pairs was greater than expected based on chance. The same was not found when examining non leader-follower pairs. Additionally, relatedness for leader-follower pairs was positively correlated with association index values, but no correlation was found for this measure in non leader-follower pairs. Interestingly, haplotypes were not frequently shared between leader-follower pairs (25%). Together, these results suggest that bottlenose dolphin leaders have the opportunity to gain indirect benefits by leading relatives. These findings provide a potential mechanism for the maintenance of leadership in a highly dynamic fission-fusion population with few obvious direct benefits to leaders.
Highlights
Group travel can be directed or suggested by a subset of individuals, generally referred to as leaders [1,2,3,4,5]
We found that leaderfollower pairs were more closely related to one another than expected based on chance, and that association frequency for these pairs was correlated with relatedness
Strong associations for male alliance pairs have been linked to relatedness in the bottlenose dolphin [17], but this result is not universal [38]
Summary
Group travel can be directed or suggested by a subset of individuals, generally referred to as leaders [1,2,3,4,5]. Followers in these groups can presumably benefit from the leader(s) locating otherwise unavailable resources or from being led to available ones more efficiently. When resources are mobile and patchy, it is just as likely that followers will locate resources at a time similar to the leader, and ‘‘finders share’’ or priority access benefits may be negligible. Given the lack of obvious immediate benefits and the certain costs to leading, indirect benefits created by helping kin locate resources may provide reason for individuals in fission-fusion groups to lead others
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