Evidence for social role in a dolphin social network

Abstract

Social animals have to take into consideration the behaviour of conspecifics when making decisions to go by their daily lives. These decisions affect their fitness and there is therefore an evolutionary pressure to try making the right choices. In many instances individuals will make their own choices and the behaviour of the group will be a democratic integration of everyone's decision. However, in some instances it can be advantageous to follow the choice of a few individuals in the group if they have more information regarding the situation that has arisen. Here I provide early evidence that decisions about shifts in activity states in a population of bottlenose dolphin follow such a decision making process. This unshared consensus is mediated by a non-vocal signal which can be communicated globally within the dolphin school. These signals are emitted by individuals that tend to have more information about the behaviour of potential competitors because of their position in the social network. I hypothesise that this decision making process emerged from the social structure of the population and the need to maintain mixed-sex schools.

Conflicts of interest and the evolution of decision sharing

“…Conradt et al in press). Next, we translate this grouplevel outcome into fitness consequences for individual group members (Conradt & Roper 2003, 2007. In this manner, we determine fitness consequences for each individual group member, depending both on its own local behaviour and on that of all other group members.…”

“…Secondly, individuals are likely to gain from moving towards their preferred spatial target and from moving towards the target preferred by other group members, and more so from the former than the latter (e.g. Conradt 1998;Ruckstuhl & Neuhaus 2000;Conradt & Roper 2003, 2007. The difference in fitness gains between moving towards a non-preferred target versus a preferred target constitutes a 'consensus cost' (Conradt & Roper 2003, 2005.…”

Maternal and Alloparental Discipline in Atlantic Spotted Dolphins (Stenalla frontalis) in the Bahamas

“…These groups of mothers may discipline their own calves, and those of their close associates. In social living animals such as dolphins, the behavior of each individual may affect the fitness of others in the group (Clutton-Brock & Parker, 1995;Lusseau, 2007). Misbehaving calves would not only affect their own survival, but that of their mother and the social unit as a whole.…”

Investigation of Group Leadership in a Fission-Fusion Species, the Bottlenose Dolphin

“…There are examples of leaders providing guidance to resource use. In another species of bottlenose dolphin (Tursiops aduncus), some dolphins provide cues for when to stop and start feeding results from knowledge of area depletion (Lusseau 2007 Whereas relatedness values based on genomic DNA were greater than expected for leader-follower pairs, the lack of shared haplotypes suggests that pairs were frequently not related maternally. Some cetaceans, e.g., Orcinus orca (Bigg et al 1987),…”