Evidence for non-random co-occurrences in a white shark aggregation

Adam Schilds, Johann Mourier, Charlie Huveneers*, Leila Nazimi, Andrew Fox, Stephan T. Leu

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    20 Citations (Scopus)

    Abstract

    Groups or aggregations of animals can result from individuals being attracted to a common resource or because of synchronised patterns of daily or seasonal activity. Although mostly solitary throughout its distribution, white sharks (Carcharodon carcharias) seasonally aggregate at a number of sites worldwide to feed on calorie-rich pinnipeds. At the Neptune Islands, South Australia, large numbers of white sharks can be sighted throughout the year, including during periods of low seal abundance. We use a combination of photo-identification and network analysis based on co-occurrence of individuals visiting the site on the same day to elucidate the population structure and aggregatory behaviour of Australia’s largest aggregation of sub-adult and adult white sharks. We photo-identified 282 sharks (183 males, 97 females, 2 unknown) over a 4.5-year period (June 2010–November 2014) and found that white sharks did not randomly co-occur with their conspecifics, but formed four distinct communities. Tendency to co-occur varied across months with males co-occurring with more individuals than females. Sex-dependent patterns of visitation at the Neptune Islands and resulting intraspecific competition likely drive the observed community structure and temporal variability in co-occurrences. This study provides new insights into the aggregatory behaviour of white sharks at a seal colony and shows for the first time that white shark co-occurrence can be non-random. 

    Original languageEnglish
    Article number138
    Pages (from-to)1-12
    Number of pages12
    JournalBehavioral Ecology and Sociobiology
    Volume73
    Issue number10
    DOIs
    Publication statusPublished - Oct 2019

    Keywords

    • Social network analysis
    • Gregariousness
    • Social behaviour
    • Aggregation
    • Photo-ID
    • Carcharodon carcharias

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