Cooperative partner choice in multi-level male dolphin alliances

Abstract

Investigations into cooperative partner choice should consider both potential and realised partners, allowing for the comparison of traits across all those available. Male bottlenose dolphins form persisting multi-level alliances. Second-order alliances of 4–14 males are the core social unit, within which 2–3 males form first-order alliances to sequester females during consortships. We compared social bond strength, relatedness and age similarity of potential and realised partners of individual males in two age periods: (i) adolescence, when second-order alliances are formed from all available associates, and (ii) adulthood, when first-order allies are selected from within second-order alliances. Social bond strength during adolescence predicted second-order alliance membership in adulthood. Moreover, males preferred same-aged or older males as second-order allies. Within second-order alliances, non-mating season social bond strength predicted first-order partner preferences during mating season consortships. Relatedness did not influence partner choice on either alliance level. There is thus a striking resemblance between male dolphins, chimpanzees and humans, where closely bonded non-relatives engage in higher-level, polyadic cooperative acts. To that end, our study extends the scope of taxa in which social bonds rather than kinship explain cooperation, providing the first evidence that such traits might have evolved independently in marine and terrestrial realms.

Mating and Reproductive Success in Free-Ranging Stump-Tailed Macaques: Effectiveness of Male–Male Coalition Formation as a Reproductive Strategy

“…Coalition formation, defined as cooperation in an aggressive or competitive context, where one animal intervenes in an ongoing conflict between two parties to support one side (Harcourt and de Waal, 1992), is one of the notable alternative tactics in males to improve their dominance-based status, which improves their mating success (Noë and Sluijter, 1990). Coalition formation in males has been reported in various mammalian taxa, e.g., cetaceans (Diaz-Aguirre et al, 2018;Gerber et al, 2021) and carnivores (Packer et al, 1991;Caro and Collins, 2010), although it has most extensively been studied in primates (van Schaik et al, 2006). Nonetheless, at present, we lack a comprehensive understanding of the proximate mechanisms underlying such cooperative coalition behaviors, i.e., who helps whom (Rodrigues and Kokko, 2016).…”

The partial merger of two dolphin societies

“…Greater participation by male WSR dolphins suggests that mating opportunities may play a role in mixed group formation, as in bonobos [ 68 ]. Spotted dolphins’ fission–fusion grouping also renders male defence of females impossible except possibly for short periods, as occurs in some bottlenose dolphins [ 53 ], whose non-kin, strategic alliances are largely developed among similar age peers that associated as juveniles [ 70 , 71 ]. The formation of male–male bonds among previously unfamiliar spotted dolphins suggests a similar strategic flexibility.…”

Social Rank or Social Bonds: Which one Facilitates Coalition Formation in Male Tibetan Macaques?

“…The results revealed that the partner choice in coalitions is related to social relationships and rank. Males choose the coalition that works best for them according to different situations [ 36 , 37 , 38 ]. In semi-free-ranging Barbary macaques, males are more likely to support maternal relatives than non-relatives, and kinship plays an important role in coalition decision-making [ 39 ].…”