Bottlenose dolphins, Tursiops cf. aduncus, in Shark Bay, Western Australia exhibit the most complex alliances known outside of humans. Advances in our understanding of these alliances have occurred ...with expansions of our study area each decade. In the 1980s, we discovered that males cooperated in stable trios and pairs (first-order alliances) to herd individual oestrous females, and that two such alliances of four to six, sometimes related, individuals (second-order alliances) cooperated against other males in contests over females. The 1990s saw the discovery of a large 14-member second-order alliance whose members exhibited labile first-order alliance formation among nonrelatives. Partner preferences as well as a relationship between first-order alliance stability and consortship rate in this ‘super-alliance’ indicated differentiated relationships. The contrast between the super-alliance and the 1980s alliances suggested two alliance tactics. An expansion of the study area in the 2000s revealed a continuum of second-order alliance sizes in an open social network and no simple relationship between second-order alliance size and alliance stability, but generalized the relationship between first-order alliance stability and consortship rate within second-order alliances. Association preferences and contests involving three second-order alliances indicated the presence of third-order alliances. Second-order alliances may persist for 20 years with stability thwarted by gradual attrition, but underlying flexibility is indicated by observations of individuals joining other alliances, including old males joining young or old second-order alliances. The dolphin research has informed us on the evolution of complex social relationships and large brain evolution in mammals and the ecology of alliance formation. Variation in odontocete brain size and the large radiation of delphinids into a range of habitats holds great promise that further effort to describe their societies will be rewarded with similar advances in our understanding of these important issues.
•We review a 30-year study on male bottlenose dolphin alliances in Shark Bay, Western Australia.•The study (Dolphin Alliance Project) describes the most complex alliance system outside of humans.•Long-term observations have contributed greatly to our understanding of these alliances.•The study provides insight into the evolution of large brains and intelligence in mammals.
Bottlenose dolphins in Shark Bay, Australia, live in a large, unbounded society with a fission-fusion grouping pattern. Potential cognitive demands include the need to develop social strategies ...involving the recognition of a large number of individuals and their relationships with others. Patterns of alliance affiliation among males may be more complex than are currently known for any non-human, with individuals participating in 2-3 levels of shifting alliances. Males mediate alliance relationships with gentle contact behaviours such as petting, but synchrony also plays an important role in affiliative interactions. In general, selection for social intelligence in the context of shifting alliances will depend on the extent to which there are strategic options and risk. Extreme brain size evolution may have occurred more than once in the toothed whales, reaching peaks in the dolphin family and the sperm whale. All three 'peaks' of large brain size evolution in mammals (odontocetes, humans and elephants) shared a common selective environment: extreme mutual dependence based on external threats from predators or conspecific groups. In this context, social competition, and consequently selection for greater cognitive abilities and large brain size, was intense.
In Shark Bay, Western Australia, male bottlenose dolphins form a complex nested alliance hierarchy. At the first level, pairs or trios of unrelated males cooperate to herd individual females. ...Multiple first-order alliances cooperate in teams (second-order alliances) in the pursuit and defence of females, and multiple teams also work together (third-order alliances). Yet it remains unknown how dolphins classify these nested alliance relationships. We use 30 years of behavioural data combined with 40 contemporary sound playback experiments to 14 allied males, recording responses with drone-mounted video and a hydrophone array. We show that males form a first-person social concept of cooperative team membership at the second-order alliance level, independently of first-order alliance history and current relationship strength across all three alliance levels. Such associative concepts develop through experience and likely played an important role in the cooperative behaviour of early humans. These results provide evidence that cooperation-based concepts are not unique to humans, occurring in other animal societies with extensive cooperation between non-kin.
Players in Axelrod and Hamilton's model of cooperation were not only in a Prisoner's Dilemma, but by definition, they were also trapped in a dyad. But animals are rarely so restricted and even the ...option to interact with third parties allows individuals to escape from the Prisoner's Dilemma into a much more interesting and varied world of cooperation, from the apparently rare ‘parcelling’ to the widespread phenomenon of market effects. Our understanding of by-product mutualism, pseudo-reciprocity and the snowdrift game is also enriched by thinking ‘beyond the dyad’. The concepts of by-product mutualism and pseudo-reciprocity force us to think again about our basic definitions of cooperative behaviour (behaviour by a single individual) and cooperation (the outcome of an interaction between two or more individuals). Reciprocity is surprisingly rare outside of humans, even among large-brained ‘intelligent’ birds and mammals. Are humans unique in having extensive cooperative interactions among non-kin and an integrated cognitive system for mediating reciprocity? Perhaps, but our best chance for finding a similar phenomenon may be in delphinids, which also live in large societies with extensive cooperative interactions among non-relatives. A system of nested male alliances in bottlenose dolphins illustrates the potential and difficulties of finding a complex system of cooperation close to our own.
Efforts to understand human social evolution rely largely on comparisons with nonhuman primates. However, a population of bottlenose dolphins in Shark Bay, Western Australia, combines a ...chimpanzee-like fission-fusion grouping pattern, mating system, and life history with the only nonhuman example of strategic multilevel male alliances. Unrelated male dolphins form three alliance levels, or “orders”, in competition over females: both within-group alliances (i.e., first- and second-order) and between-group alliances (third-order), based on cooperation between two or more second-order alliances against other groups. Both sexes navigate an open society with a continuous mosaic of overlapping home ranges. Here, we use comprehensive association and consortship data to examine fine-scale alliance relationships among 121 adult males. This analysis reveals the largest nonhuman alliance network known, with highly differentiated relationships among individuals. Each male is connected, directly or indirectly, to every other male, including direct connections with adult males outside of their three-level alliance network. We further show that the duration with which males consort females is dependent upon being well connected with third-order allies, independently of the effect of their second-order alliance connections, i.e., alliances between groups increase access to a contested resource, thereby increasing reproductive success. Models of human social evolution traditionally link intergroup alliances to other divergent human traits, such as pair bonds, but our study reveals that intergroup male alliances can arise directly from a chimpanzee-like, promiscuous mating system without one-male units, pair bonds, or male parental care.
Social and vocal complexity in bottlenose dolphins King, Stephanie L.; Connor, Richard C.; Montgomery, Stephen H.
Trends in neurosciences (Regular ed.),
December 2022, 2022-12-00, 20221201, Letnik:
45, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Bottlenose dolphins are highly social, renowned for their vocal flexibility, and possess highly enlarged brains relative to their body size. Here, we discuss some of the defining features of ...bottlenose dolphin social and vocal complexity and place this in the context of their cognitive evolution.
Synchronous displays are hallmarks of many animal societies, ranging from the pulsing flashes of fireflies, to military marching in humans. Such displays are known to facilitate mate attraction or ...signal relationship quality. Across many taxa, synchronous male displays appear to be driven by competition, while synchronous displays in humans are thought to be unique in that they serve a cooperative function. Indeed, it is well established that human synchrony promotes cooperative endeavours and increases success in joint action tasks. We examine another system in which synchrony is tightly linked to cooperative behaviour. Male bottlenose dolphins form long-lasting, multi-level, cooperative alliances in which they engage in coordinated efforts to coerce single oestrus females. Previous work has revealed the importance of motor synchrony in dolphin alliance behaviour. Here, we demonstrate that allied dolphins also engage in acoustic coordination whereby males will actively match the tempo and, in some cases, synchronize the production of their threat vocalization when coercing females. This finding demonstrates that male dolphins are capable of acoustic coordination in a cooperative context and, moreover, suggests that both motor and acoustic coordination are features of coalitionary behaviour that are not limited to humans.
The evolutionary forces that drive fitness variation in species are of considerable interest. Despite this, the relative importance and interactions of genetic and social factors involved in the ...evolution of fitness traits in wild mammalian populations are largely unknown. To date, a few studies have demonstrated that fitness might be influenced by either social factors or genes in natural populations, but none have explored how the combined effect of social and genetic parameters might interact to influence fitness. Drawing from a long-term study of wild bottlenose dolphins in the eastern gulf of Shark Bay, Western Australia, we present a unique approach to understanding these interactions. Our study shows that female calving success depends on both genetic inheritance and social bonds. Moreover, we demonstrate that interactions between social and genetic factors also influence female fitness. Therefore, our study represents a major methodological advance, and provides critical insights into the interplay of genetic and social parameters of fitness.
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