Richard C. Connor

Fission-Fusion Dynamics: New Research Frameworks

Renewed interest in fission‐fusion dynamics is due to the recognition that such dynamics may create unique challenges for social interaction and distinctive selective pressures acting on underlying communicative and cognitive abilities. New frameworks for integrating current knowledge on fission‐fusion dynamics emerge from a fundamental rethinking of the term “fission‐fusion” away from its current general use as a label for a particular modal type of social system (i.e., “fission‐fusion societies”). Specifically, because the degree of spatial and temporal cohesion of group members varies both within and across taxa, any social system can be described in terms of the extent to which it expresses fission‐fusion dynamics. This perspective has implications for socioecology, communication, cognitive demands, and human social evolution.

Cognitive dysfunction in psychiatric disorders: characteristics, causes and the quest for improved therapy

Studies of psychiatric disorders have traditionally focused on emotional symptoms such as depression, anxiety and hallucinations. However, poorly controlled cognitive deficits are equally prominent and severely compromise quality of life, including social and professional integration. Consequently, intensive efforts are being made to characterize the cellular and cerebral circuits underpinning cognitive function, define the nature and causes of cognitive impairment in psychiatric disorders and identify more effective treatments. Successful development will depend on rigorous validation in animal models as well as in patients, including measures of real-world cognitive functioning. This article critically discusses these issues, highlighting the challenges and opportunities for improving cognition in individuals suffering from psychiatric disorders.

Cetacean societies : field studies of dolphins and whales

Long-lived, slow to reproduce, and often hidden beneath the waters surface, whales and dolphins (cetaceans) have remained elusive subjects for scientific study even though they have fascinated humans for centuries. Until recently, much of what we knew about cetaceans came from commercial sources such as whalers and trainers for dolphin acts. Innovative research methods and persistent efforts, however, have begun to penetrate the depths to reveal tantalizing glimpses of the lives of these mammals in their natural habitats. This book presents a comprehensive synthesis and review of these studies. Groups of chapters focus on the history of cetacean behavioural research and methodology; state-of-the-art reviews of information on four of the most-studied species: bottlenose dolphins, killer whales, sperm whales and humpback whales; and summaries of major topics, including group living, male and female reproductive strategies, communication, and conservation drawn from comparative research on a wide range of species. Written by cetacean scientists, this volume should be of benefit to students of cetology and researchers in other areas of behavioral and conservation ecology, as well as anyone with a serious interest in the world of whales and dolphins.

Social evolution in toothed whales

Two contrasting results emerge from comparisons of the social systems of several odontocetes with terrestrial mammals. Researchers have identified remarkable convergence in prominent features of the social systems of odontocetes such as the sperm whale and bottlenose dolphin with a few well-known terrestrial mammals such as the elephant and chimpanzee. In contrast, studies on killer whales and Bairds beaked whale reveal novel social solutions to aquatic living. The combination of convergent and novel features in odontocete social systems promise a more general understanding of the ecological determinants of social systems in both terrestrial and aquatic habitats, as well as the relationship between relative brain size and social evolution.

Complex social structure, alliance stability and mating access in a bottlenose dolphin 'super-alliance'.

Large brain size in mammals has been related to the number and complexity of social relationships, particularly social alliances within groups. The largest within–group male alliance known outside of humans is found in a social network (>400) of Indian Ocean bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia. Members of this dolphin ‘super–alliance’ cooperate against other alliances over access to females. Males within the super–alliance form temporary trios and occasionally pairs in order to consort with individual females. The frequent switching of alliance partners suggests that social relationships among males within the super–alliance might be relatively simple and based on an ‘equivalence rule’, thereby allowing dolphins to form large alliances without taxing their ‘social intelligence’. The equivalence model predicts that the 14 males in the super–alliance should not exhibit differences in alliance stability or partner preferences. However, data from 100 consortships do not support the equivalence hypothesis. The 14 males exhibited striking differences in alliance stability and partner preferences suggesting that the super–alliance has a complex internal structure. Further, within the super–alliance, alliance stability correlates with consortship rate, suggesting that differentiated relationships within the super–alliance are based on competition for access to females.

Superalliance of bottlenose dolphins

It is quite common to find several levels of nested male alliances in human political organization, but these are extremely rare in other species. Yet we found that male bottlenose dolphins (Tursiops sp.) at Shark Bay, Western Australia, form two levels of alliance within a social network of more than 400 individuals. Fourteen of the males formed highly labile alliances, rather than the more typical stable ones, and joined forces in a large ‘superalliance’ that competed directly with smaller teams of stable alliances.

Dolphin social intelligence: complex alliance relationships in bottlenose dolphins and a consideration of selective environments for extreme brain size evolution 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.

A division of labour with role specialization in group-hunting bottlenose dolphins (Tursiops truncatus) off Cedar Key, Florida.

Individual role specialization during group hunting is extremely rare in mammals. Observations on two groups of bottlenose dolphins (Tursiops truncatus) in Cedar Key, Florida revealed distinctive behavioural roles during group feeding. In each group, one individual was consistently the ‘driver’, herding the fishes in a circle toward the remaining ‘barrier’ dolphins. Aerial fish–capture rates differed between groups, as well as between the driver and barrier dolphins, in one group but not in the other. These differences between the two groups may reflect differences in group stability or in prey school size.

Aggression in bottlenose dolphins: Evidence for sexual coercion, male-male competition, and female tolerance through analysis of tooth-rake marks and behaviour

Aggressive behaviour is rarely observed, but may have a large impact on the social structure, relationships and interactions in animal societies. Long-term behavioural study of Indian Ocean bottlenose dolphins in Shark Bay, Australia, suggests that males are more aggressive than females, and use sexual coercion during the breeding season, but age and sex-specific patterns of aggression have not been well documented. We analyzed tooth rake marks, an indirect measure of received conspecific aggression, to determine such patterns by age, sex, and adult female reproductive state. Photographs of 224 Shark Bay bottlenose dolphins were examined for tooth rakes and each rake was categorized as new (broken skin), obvious (white rake lines that are clearly visible) or faint (faint evidence of rakes). Rake lines were also coded by each body section visible in the photograph. Cycling females (those that became pregnant within 6 mos. of the photograph date) were significantly more likely to have new tooth rakes than non-cycling females (pregnant or with a dependent calf 2 years apart) suggests that the marks are not cumulative. Overall, 83% of the population has tooth rake marks, suggesting that agonistic interactions occur for most individuals at least every two years. Analysis of gonistic interactions for 55 adult focal females (observed for 1960 h) and their 88 calves (observed for 1876 h) show that female aggression is extremely rare (occurring every 490 h), but females receive aggression more often (every 61 h), and 84% of received aggression was from juvenile and adult males. Focal adult females were never observed acting aggressively towards juveniles or adults of either sex, suggesting that female bottlenose dolphins are highly tolerant. Of the four observed instances of adult female aggression, all were directed at their dependent offspring. Male calves are significantly more aggressive than female calves, and calves had higher rates of agonistic interactions than their mothers (every 18 h), even though calves had fewer tooth rakes than all other age classes. The patterns of tooth rake presence and prevalence likely result from sexual coercion of adult females by adult males and intra-sexual male competition.

Social and genetic interactions drive fitness variation in a free-living dolphin population

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.