Patterns of association among bottlenose dolphins resident in Shark Bay, Western Australia were analyzed using party membership data. Parties contained an average of 4.8 individuals, but party size and composition were unstable. While these temporary parties often contained both males and females, long term consistent associations generally were between members of the same sex. The highest association coefficients, resulting from very frequent co-occurrence within parties were between males and between mothers and offspring. Males formed subgroups of two or three individuals who consistently associated with each other, and these were stable over periods of at least seven years in some cases. Male subgroups preferentially associated with particular other male subgroups. Females associated most consistently with other females, although not to the same extent as some males. Female associations were better described as a network rather than discrete subgroups. Male-female associations were generally inconsistent and depended in part on female reproductive state. Mothers and their offspring associated very consistently for at least 4 years.

In Shark Bay, Western Australia, male bottlenose dolphins (Tursiops sp.) cooperate in pairs and triplets to sequester and control the movements of females. We refer to this behavior as "herding" and to the male pairs and triplets as alliances. During a 25-month study (1987-1989) on the social relationships of males, we documented herding in 10 alliances. Males preferentially herded nonpregnant females likely to be in estrus. Alliance members associated with one another consistently when not herding females. Each alliance associated preferentially with one or two other alliances. Occasionally, two alliances combined and took females from another alliance or defended females against such efforts. This study documents multiple-level male alliances within a social group outside of humans.

Here we report that synchronous surfacing in male bottlenose dolphins is associated with alliance membership and that synchrony between members of cooperating alliances is more common during social behaviour than during nonsocial behaviour, especially during bouts of 'intense' social behaviour (e.g. mounting, displays, chasing) with female consorts. Alliances of three males varied in the degree to which all members participated in synchrony, possibly reflecting differences in alliance unity and the extent to which alliances consort with females. The lack of a discontinuity between the elaborate displays that males perform around females and the synchronous surfacing of alliance members reported here suggest that synchrony is an adaptive signal. If so, we have a remarkable convergence in the use of synchrony as an alliance signal in humans and bottlenose dolphins. However, whether an adaptive signal or a correlate of proximity, synchrony will be a useful tool in the study of delphinid social relationships.

We examine the contexts and patterns of "signature" whistle production by wild bottlenose dolphin mother-infant pairs (Tursiops spp.) to gain insight into the functional significance of whistles. Results are based on focal observations and simultaneous recordings of underwater vocalizations. Whistles occur primarily when mother-infant pairs are separated, and the probability of whistles increases with distance of separation. The timing of whistles during separations varies, but whistles tend to be produced in repetitive series and are generally concentrated toward the later stages of the separation, i.e., during the process of reunion. Although we focused on infants, mothers do not appear to whistle during separations as frequently as infants. Infant whistles may function to facilitate reunions by conveying information to the mother concerning the infant's motivation to reunite and/or its location. Infant whistles could induce a cooperative response from the mother including approach, slowing to allow the infant to catch up or whistling. Highly individualized signature whistles may be particularly useful in a fission-fusion society in which individuals (mothers and infants as well as adults) join and leave temporary parties in a fluid manner, yet maintain consistent, long-term associations with particular individuals.

J. 8. BF.KGC;KT:N, P. 1997: Sponge carving by dolphins (Delphinidae, Turrip sp.): a foraging speciabzation involving tool use? F,thology 103, 4.54465. AbstractDuring long-term research on bottlenose dolphins (Tursiops sp.) in Shark Bay, K'estern Australia, sevcral individuals were observed carrying sponges, lici,inodic!pum mesemterinum, on their rostra. Over multiple years, five regularly sighted individuals were usually carrying sponges when encountered (67-100 "%I of encounters). Four additional regularly sighted individuals were observed with sponges lust one timr each. All fix e individuals that routinely carried sponges were female. Two of the anomalous, one-timc carriers were female, one was likely female, and one was male. Most observations of sponge carrying occurred within a restricted .ires, a relati~ deep water channel (8-10 m deep). Surface observations of sponge carrying, including focal animal observations, revealed a stereotyped surfacing and diving pattern, and occasional indications of prey consumption. Three hypotheses are considered regarding the function of sponge carrying: 1. dolphins wcrc playing with the s p t q e s ; 2. the sponges contain some compound of use to the dolphins (e.g. for medicinal purposes); and 3. the sponges were used as a tool to aid in foraging. The foraging tool hypothesis is hest supported, but thc exact manner in which sponges are used remains to be discovered. Sponge carrying is a beharioural specia'iTation, probably involving foraging, and regularly engaged in by onl! a small proportion of female dolphins in Shark BaJ-.