G’day Marmamers,

We’re very pleased to circulate a couple more papers from our long-term dolphin research in the eastern and western gulfs of Shark Bay (www.sharkbaydolphins.org).

Published in June was:

Bizzozzero MR, Allen SJ, Gerber L, King SL, Wild S, Connor RC, Friedman W, Wittwer S, Krützen M 2019. Tool use and alliance partner choice in male bottlenose dolphins. Proceedings of the Royal Society B 286: 20190898. http://dx.doi.org/10.1098/rspb.2019.0898

Abstract: Homophilous behaviour plays a central role in the formation of human friendships. Individuals form social ties with others that show similar phenotypic traits, independently of relatedness. Evidence of such homophily can be found in bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia, where females that use marine sponges as foraging tools often associate with other females that use sponges. ‘Sponging’ is a socially learned, time-consuming behaviour, transmitted from mother to calf. Previous research illustrated a strong female bias in adopting this technique. The lower propensity for males to engage in sponging may be due to its incompatibility with adult male-specific behaviours, particularly the formation of multi-level alliances. However, the link between sponging and male behaviour has never been formally tested. Here, we show that male spongers associated significantly more often with other male spongers irrespective of their level of relatedness. Male spongers spent significantly more time foraging, and less time resting and travelling, than did male non-spongers. Interestingly, we found no difference in time spent socializing. Our study provides novel insights into the relationship between tool use and activity budgets of male dolphins, and indicates social homophily in the second-order alliance composition of tool-using bottlenose dolphins. 

And published earlier this week (and open access) was:

King SL, Allen SJ, Krützen M and Connor RC 2019. Vocal behaviour of allied male dolphins during cooperative mate guarding. Animal Cognition https://doi.org/10.1007/s10071-019-01290-1

Abstract: Coercive mate guarding, where males use aggression to control female movements, is a form of sexual coercion which functions to constrain female mate choice. Non-human primates, for example, herd females to keep them away from competing males, but male bottlenose dolphins (Tursiops aduncus) also herd females to keep them close to their alliance partners. Indeed, pairs and trios of male dolphins work together to sequester single estrus females and defend them from competing alliances. Yet how males facilitate such coordination remains unknown. Here, we investigate the vocal behaviour of allied male bottlenose dolphins during the herding of individual females, examining how the production of whistles and ‘pops’ (a threat vocalisation) varied with behavioural state and inter-animal distances. Allied males produced both whistles and pops significantly more often and at higher rates during social interactions, though they differed in function. Whistle rates increased significantly when new individuals joined the consorting group, consistent with previous work showing that whistles are part of a greeting sequence for this species. Whistle matching also appeared to play a role in within-alliance coordination. Pop vocalisations increased significantly when the nearest male to the female changed, likely inducing the female to remain close as the males coordinate a guard switch. Building upon prior research examining female movements in response to pops, we show that males approach the female and current guard whilst popping, leading to a guard switch. Our results provide new insights into the use of vocal signals during cooperative mate guarding between allied male dolphins.

All the best, Simon

~~~~~~~~~~~~~

Dr Simon J Allen 

School of Biological Sciences

University of Bristol

Bristol BS8 1TQ UK

Mob: +44 (0) 77047 53101

Email: Simon.Allen@bristol.ac.uk

Web: http://www.sharkbaydolphins.org

Twitter: @SimonJAllen1

Recent papers: Declines in dolphin survival and reproduction following a heatwave https://www.cell.com/current-biology/fulltext/S0960-9822(19)30217-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982219302179%3Fshowall%3Dtrue
Dolphins retain individual vocal labels in multi-level alliances https://www.cell.com/current-biology/fulltext/S0960-9822(18)30615-8

Sexual displays involving sponges in Australian humpback dolphins http://rdcu.be/w3tL

Abundance and fidelity of dolphins to a trawl fishery https://www.nature.com/articles/s41598-017-05189-0