Hal Whitehead

Culture in whales and dolphins

Studies of animal culture have not normally included a consideration of cetaceans. However, with several long-term field studies now maturing, this situation should change. Animal culture is generally studied by either investigating transmission mechanisms experimentally, or observing patterns of behavioural variation in wild populations that cannot be explained by either genetic or environmental factors. Taking this second, ethnographic, approach, there is good evidence for cultural transmission in several cetacean species. However, only the bottlenose dolphin (Tursiops) has been shown experimentally to possess sophisticated social learning abilities, including vocal and motor imitation; other species have not been studied. There is observational evidence for imitation and teaching in killer whales. For cetaceans and other large, wide-ranging animals, excessive reliance on experimental data for evidence of culture is not productive; we favour the ethnographic approach. The complex and stable vocal and behavioural cultures of sympatric groups of killer whales (Orcinus orca) appear to have no parallel outside humans, and represent an independent evolution of cultural faculties. The wide movements of cetaceans, the greater variability of the marine environment over large temporal scales relative to that on land, and the stable matrilineal social groups of some species are potentially important factors in the evolution of cetacean culture. There have been suggestions of gene-culture coevolution in cetaceans, and culture may be implicated in some unusual behavioural and life-history traits of whales and dolphins. We hope to stimulate discussion and research on culture in these animals.

SOCPROG programs: analysing animal social structures

SOCPROG is a set of programs which analyses data on animal associations. Data usually come from observations of the social behaviour of individually identifiable animals. Associations among animals, sampling periods, restrictions on the data and association indices can be defined very flexibly. SOCPROG can analyse data sets including 1,000 or more individuals. Association matrices are displayed using sociograms, principal coordinates analysis, multidimensional scaling and cluster analyses. Permutation tests, Mantel and related tests and matrix correlation methods examine hypotheses about preferred associations among individuals and classes of individual. Weighted network statistics are calculated and can be tested against null hypotheses. Temporal analyses include displays of lagged association rates (rates of reassociation following an association). Models can be fitted to lagged association rates. Multiple association measures, including measures produced by other programs such as genetic or range use data, may be analysed using Mantel tests and principal components analysis. SOCPROG also performs mark-recapture population analyses and movement analyses. SOCPROG is written in the programming language MATLAB and may be downloaded free from the World Wide Web.

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.

MALE COMPETITION IN LARGE GROUPS OF WINTERING HUMPBACK WHALES

Fast moving groups containing three or more adult humpback whales are found in the winter on Silver Bank in the West Indies, and off Hawaii. Many of these groups have a definite structure: a central Nuclear Animal, with or without a calf, is surrounded by escorts who compete, sometimes violently, for proximity to the Nuclear Animal. This competition involves fluke thrashes, the blowing of bubblestreams, and physical contact, some of which appears designed to hurt an opponent: bleeding wounds are seen on the competing escorts. Escorts sometimes leave these groups and start singing, and singers sometimes stop to join large groups. The pattern of interactions strongly suggests that the escorts are males competing for access to a central female. Off Hawaii singers respond to such groups at ranges of up to approximately 7.5 km. On Silver Bank, Principal Escorts maintained a position of closest proximity to the Nuclear Animal for an average of 7.5 hours before replacement.

Interpreting short-term behavioural responses to disturbance within a longitudinal perspective

We documented immediate, behavioural responses of Indo-Pacific bottlenose dolphins (Tursiops sp.) to experimental vessel approaches in regions of high and low vessel traffic in Shark Bay, Western Australia. Experimental vessel approaches elicited significant changes in the behaviour of targeted dolphins when compared with their behaviour before and after approaches. During approaches, focal dolphin groups became more compact, had higher rates of change in membership and had more erratic speeds and directions of travel. Dolphins in the region of low vessel traffic (control site) had stronger and longer-lasting responses than did dolphins in the region of high vessel traffic (impact site). In the absence of additional information, the moderated behavioural responses of impact-site dolphins probably would be interpreted to mean that long-term vessel activity within a region of tourism had no detrimental effect on resident dolphins. However, another study showed that dolphin-watching tourism in Shark Bay has contributed to a long-term decline in dolphin abundance within the impact site (Bejder et al., in press, Conservation Biology). Those findings suggest that we documented moderated responses not because impact-site dolphins had become habituated to vessels but because those individuals that were sensitive to vessel disturbance left the region before our study began. This reinterpretation of our findings led us to question the traditional premise that short-term behavioural responses are sufficient indicators of impacts of anthropogenic disturbance on wildlife.

Analysing animal social structure

Abstract This paper presents a framework for analysing the social structure of populations in which interactions between some identified individuals can be observed. Statistics describing the nature, quality and temporal patterning of one or more interaction measures are used to define relationships between pairs of individuals or classes of individual. Multivariate techniques can then be used to display the social structure of the population. These displays indicate the social complexity of the population and can be used to classify relationships and examine patterns of relationship between classes of animal. They can also be used to define and delineate groups. This framework and these techniques should be particularly useful when analysing complex fission–fusion societies, as are found among the primates and cetaceans. 1997 The Association for the Study of Animal Behaviour

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.

Identification of Humpback Whales by Fluke Photographs

Among the large baleen whales, humpbacks are notable for the variety of different white and black patterns and slight morphological differences which can be observed between individuals (Lillie, 1915; Matthews, 1937; Pike, 1953; Schevill and Backus, 1960). Observations in the field and inspection of photographs suggest that variations in the shape of the dorsal fin or in the disposition of body scars can sometimes be used to identify individual humpback whales. It is primarily the pattern on the underside of the flukes which appears to us to provide the most positive discrimination between individual humpback whales. This pattern varies from nearly all white to nearly all black, but characteristically contains a variety of black or white patches, lines or streaks.

Babysitting, dive synchrony, and indications of alloparental care in sperm whales

Abstract Young sperm whales (Physeter macrocephalus) serially accompany different members of their social group at the surface while the majority of the group is foraging at depth. The presence of a nearby larger whale is likely to increase the survival prospects of the young animal. In studies off the Galápagos Islands, first-year calves were less likely to be seen at the surface alone than were larger whales, and groups containing calves showed less synchronous diving behaviour – shorter intervals with no larger whales at the surface – than those without calves. This difference in diving synchrony was not solely the result of behaviour by individuals assumed to be the mothers of calves (as they spent a disproportionate amount of time accompanying them). Thus babysitting in sperm whales seems to be a form of alloparental care. Its benefit may have been an important factor in the evolution of sociality in female sperm whales.

Vocal clans in sperm whales (Physeter macrocephalus).

Cultural transmission may be a significant source of variation in the behaviour of whales and dolphins, especially as regards their vocal signals. We studied variation in the vocal output of ‘codas’ by sperm whale social groups. Codas are patterns of clicks used by female sperm whales in social circumstances. The coda repertoires of all known social units (n = 18, each consisting of about 11 females and immatures with long–term relationships) and 61 out of 64 groups (about two social units moving together for periods of days) that were recorded in the South Pacific and Caribbean between 1985 and 2000 can be reliably allocated into six acoustic ‘clans’, five in the Pacific and one in the Caribbean. Clans have ranges that span thousands of kilometres, are sympatric, contain many thousands of whales and most probably result from cultural transmission of vocal patterns. Units seem to form groups preferentially with other units of their own clan. We suggest that this is a rare example of sympatric cultural variation on an oceanic scale. Culture may thus be a more important determinant of sperm whale population structure than genes or geography, a finding that has major implications for our understanding of the species’ behavioural and population biology.