Behaviourally specific preferred associations in bottlenose dolphins, Tursiops spp.

Abstract

Abstract:We investigated association patterns of 52 photographically identified, free-ranging bottlenose dolphins (Tursiops spp. Gervais, 1855) across four behavioural states (rest, travel, social, and foraging/feeding) to investigate how behavioural state influences patterns of association. Group composition and behavioural data were extracted from 2178 encounter surveys collected over 3 years. Analyses revealed three general types of association: (1) affiliates, which consistently demonstrate preferred associations across all behavioural states; (2) acquaintances, which never form preferred associations but still associate in at least one behavioural state; and (3) behavioural associates, which form preferred associations in at least one, but not all behavioural states. The majority of associations in Shark Bay, Australia, are acquaintance type (38.2%), with affiliates (5.7%, principally between adult males) and behavioural associates (28.9%, principally between juveniles) being relatively rarer. Permutation tests identified behaviourally specific preferred associations during all behavioural states. Although behaviourally specific preferred associations appear to exist within the Shark Bay social structure, it seems that the social organization and mating system constrain the social relationships for the majority of males and females in differing ways which prevent them from having behavioural associates, leaving juveniles free to associate based on short-term expediency and behavioural specific needs.Résumé : Nous avons étudié les patrons d'association entre 52 grands dauphins (Tursiops spp. Gervais, 1855) libres en nature et identifiés par photographies pendant quatre états comportementaux (repos, déplacement, interaction sociale et recherche de nourriture/alimentation), afin de déterminer de quelle manière l'état comportemental affecte les patrons d'association. Nous avons tiré les données sur la composition des groupes et sur le comportement de 2178 inventaires de rencontres faits au cours de 3 années. Les analyses indiquent l'existence de trois types généraux d'associés, (1) les affiliés qui exhibent régulièrement des associations préférentielles, indépendamment de leur état comportemental, (2) les connaissances qui ne forment jamais d'association préférentielle, mais qui s'associent tout de même pendant au moins un état comportemental et (3) les associés comportementaux qui forment des associations préférentielles dans au moins un, mais pas l'ensemble, de leurs états comportementaux. La plupart des associés à Shark Bay, Australie, sont du type des connaissances (38,2 %), les autres types, soit les affiliés (5,7 % surtout des mâles adultes) et les associés comportementaux (28,9 % surtout des jeunes), étant relativement plus rares. Des tests de permutation permettent d'identifier des associations préférentielles spécifiques au comportement dans chacun des états comportementaux. Bien que des associations préférentielles spécifiques en fonction du comportement semblent exister dans la structure sociale de S...

Inter-individual association levels correlate to behavioral diversity in coastal bottlenose dolphins (Tursiops truncatus) from the Southwestern Gulf of Mexico

“…Societies are believed to gain from all the variety in their associations (Dunbar 1989); however, even in fission-fusion societies, partners could be selected to maximize efficiency or benefits while joining to develop their activities (Gero et al 2005). In this study, up to 94 % of all possible paired associations were non-significant, reaffirming the fluid nature of the community; however, 78 % of the non-random pairs exhibited moderate to high membership (Figure 4).…”

“…The positive correlation between the level of association and the diversity of activities ( Figure 6) was expected, as the context of the interactions between dyad members should become richer over time (Gero et al 2005); however, the fact that 17 of the 237 significant dyads involved partnerships with specific purposes suggests that only a handful of these individuals find larger benefits from exploiting the specific abilities of selected partners. Lusseau et al (2006) evidenced the importance of roles for specific individuals within a social network, where previous knowledge of group members and reduced number of participants helped to coordinate actions and facilitated cooperation; however such interactions were rare and deserve further attention.…”

“…COA values were categorized as infrequent (0.0 -0.2), casual (0.2 -0.4), fair, (0.4 -0.6), moderate (0.6 -0.8) or strong (0.8 -1.0; Smolker et al 1992;Quintana-Rizzo and Wells 2001). Also, to prevent the occurrence of artificial dyads (i. e. individuals photographed together by chance due to our inclusive definition of group), a preferred/avoided partner assessment was developed through a permutation test Bejder et al 1998;Gero et al 2005).…”

Social networks reveal cultural behaviour in tool-using dolphins

“…We do not argue that foraging type is the primary determinant of association. Dolphin association is likely to be driven by multiple factors, including a suite of contexts such as behavioural state 42 , foraging type, the history of interactions, reproductive state, and enduring traits such as sex 25,26,31 , kinship 30,43 , age 44 and geography 30 . Homophily on a variety of traits has a critical role in human (sub)cultures 22 and this may be true for dolphin society as well.…”

Evidence for vocal learning in juvenile male killer whales,Orcinus orca, from an adventitious cross-socializing experiment

“…Würsig and Würsig, 1979;Gero et al, 2005;Connor et al, 2006), which has also been applied to the killer whale (Ford, 1984;Jacobsen, 1986). We defined synchronous swimming (SS) as time spent swimming in the same direction within one body length.…”