Alliances among male bottlenose dolphins and a comparative analysis of mutualism.

Alliances are a common feature of animal social behavior. Animals which live in relatively closed groups, such as a lion pride or baboon troop, commonly ally with other group members in agonistic interactions with non-members. Alliances formed by group members against members of their own group are rare in non-primates. I document alliances among males within a large social network ($>$300) of bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia. Males, in stable alliances of 2-3 individuals, cooperate to aggressively herd females. Herding is partly enforced by a low frequency, click-train vocalization called "pops." Herding is a valuable indicator of a female's reproductive state. Males preferentially herd non-pregnant females, and although births are strongly seasonal, herding occurs during all months of the year. Two alliances may cooperates as "second-order alliances" to aggressively take females being herded by other alliances. Interactions among pairs and triplets share many features with interactions among individual male primates. Alliances are a form of mutualism. A mutualism is any interaction between organisms in which both (or all) participants expect to benefit. Previous analysis of intraspecific mutualisms have focused on the mechanisms by which individuals exchange benefits (e.g. nepotism, reciprocity). I continue in this tradition by presenting two kinds of mechanisms which mediate the transfer of benefits among conspecifics: "pseudo-reciprocity" and "strategy manipulation". Both mechanisms resemble reciprocity in that benefits are exchanged in sequential interactions, but cheating is not possible in pseudo-reciprocity, and not profitable in strategy manipulation. I present a general classification of mutualism constructed from the three basic mechanisms that produce benefits in a mutualism: (1) individuals acting on their own behalf may confer benefits on others incidentally, (2) individuals may perform costly acts for others, or invest in them, in anticipation of a return, and (3) individuals may parasitize or "purloin" benefits from others. This analysis yields new generalizations about intra as well as interspecific mutualism.PhDBiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105071/1/9116155.pdfDescription of 9116155.pdf : Restricted to UM users only