Assessing social structure: a data-driven approach to define associations between individuals

Sara B. Tavares, Hal Whitehead, Thomas Doniol-Valcroze

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Our interpretation of animal social structures is inherently dependent on our ability to define association criteria that are biologically meaningful. However, association thresholds are often based upon generalized preconceptions of a species’ social behaviour, and the impact of using these arbitrary definitions has been largely overlooked. In this study we suggest a probability-based method for defining association thresholds using lagged identification rates on photographic records of identifiable individuals. This technique uses a simple model of emigration/immigration from photographable clusters to identify the time-dependent lag value between identifications of two individuals that corresponds to approximately 75% probability of being in close spatial proximity and likely associating. This lag value is then used as the threshold to define associations for social analyses. We applied the technique to a dataset of northern resident killer whales (Orcinus orca) in the Northeast Pacific and tested its performance against two arbitrary thresholds. The probabilistic association maximized the variation in association strengths at different levels of the social structure, in line with known social patterns in this population. Furthermore, variability in inferred social structure metrics generated by different association criteria highlighted the consequential effect of choosing arbitrary thresholds. Data-driven association thresholds are a promising approach to study populations without the need to subjectively define associations in the field, especially in societies with prominent fission–fusion dynamics. This method is applicable to any dataset of sequential identifications where it can be assumed that associated individuals will tend to be identified in close proximity.

Original languageEnglish
JournalMammalian Biology
DOIs
Publication statusAccepted/In press - 2022

Bibliographical note

Funding Information:
This study was supported by a Visiting Fellowship from the Natural Sciences and Engineering Research Council of Canada (NSERC; Grant Number #520533-2018 to SBT) and by the Species at Risk Programme, Fisheries and Oceans Canada.

Publisher Copyright:
© 2022, The Author(s).

ASJC Scopus Subject Areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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