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A biologging perspective to the drivers that shape gregariousness in dusky dolphins

Authors
  • Pearson, Heidi C.1
  • Jones, Peter W.2
  • Brandon, Taelor P.1
  • Stockin, Karen A3
  • Machovsky-Capuska, Gabriel E.2
  • 1 University of Alaska Southeast, 11066 Auke Lake Way, Juneau, AK, 99801, USA , Juneau (United States)
  • 2 The University of Sydney, Sydney, Australia , Sydney (Australia)
  • 3 Massey University, Auckland, New Zealand , Auckland (New Zealand)
Type
Published Article
Journal
Behavioral Ecology and Sociobiology
Publisher
Springer Berlin Heidelberg
Publication Date
Nov 22, 2019
Volume
73
Issue
11
Identifiers
DOI: 10.1007/s00265-019-2763-z
Source
Springer Nature
Keywords
License
Yellow

Abstract

AbstractKnowledge of proximate (causation and development) and ultimate (evolution and survival function) causes of gregariousness is necessary to advance our knowledge of animal societies. Delphinids are among the most social taxa; however, fine-scale understanding of their intra-specific relationships is hindered by the need for underwater observations on individuals. We developed a non-invasive animal-borne camera system with the goal of examining influences on gregariousness in dusky dolphins (Lagenorhynchus obscurus). We analyzed video and diving records from 11 individual dusky dolphins off Kaikoura, New Zealand. We examined the influence of biologger attachment on dolphin behavior and tested hypotheses regarding the effects of physiology, predation, and inter-individual variation on conspecific interactions. Dolphins did not exhibit increased rates of descent or ascent in the minutes immediately following biologger attachment, indicating a lack of behavioral response. Respiration rate was positively related to dive depth and duration, suggesting that diving is energetically expensive for this species. Gregariousness was negatively related to dive depth providing evidence that the physiological constraints of diving are likely to limit social behavior. Calves were not observed more frequently in infant (vs. echelon) position with increasing depth, highlighting the likelihood of other anti-predation strategies (e.g., dilution effect) in mother-calf pairs. We found that gregariousness differed between individuals within similar social groups, suggesting the importance of collecting data at the individual level. The evidence presented herein suggests that the further development of animal-borne camera systems will yield further insight into the mechanisms underlying delphinid social behavior.Significance statementDolphins are highly social and thus excellent model species for examining the cause and function of gregariousness. However, their cryptic nature poses a challenge to collecting the fine-scale data at the individual level required to conduct rigorous hypothesis tests. We overcame this obstacle by deploying a non-invasive cutting-edge biologger on free-ranging dusky dolphins to collect information on diving behavior, physiology, gregariousness, and mother-calf strategies. Results indicate that diving is energetically expensive, even to relatively shallow depths, and these costs likely hinder gregariousness at depth. Individual differences in gregariousness were apparent and as expected in this fission-fusion society. Unexpectedly, mother-calf pairs appeared to utilize strategies other than spatial positioning to minimize predation risk. This study advanced knowledge of dolphin social life and helps to improve the degree of data resolution in cetaceans to a level on par with terrestrial studies.

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