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

  • Adam Schilds
  • Johann Mourier
  • Charlie HuveneersEmail author
  • Leila Nazimi
  • Andrew Fox
  • Stephan T. Leu
Original Article


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.

Significance statement

White sharks are top marine predators that are typically solitary but can also form aggregations around seal colonies to feed. Using a combination of photo-identification and network analysis, we investigated the co-occurrence patterns of white sharks. We showed, for the first time, that white sharks form non-random associations with conspecifics. We hypothesise that the observed sex-dependant variations in co-occurrence are linked to intraspecific competition for resources, providing new insights into the aggregatory behaviour of white sharks at a seal colony. Our study adds to the growing literature of animals showing non-random interaction or co-occurrence patterns, providing important comparative knowledge for other researchers as it broadens our knowledge to marine top predators.


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



We thank Rachel Robbins who initiated the use of photo-identification at the Neptune Islands to assess the white shark population dynamics. We also thank Tullio Rossi from Animate Your Science ( for designing the white shark photo-identification catalogue. A large number of volunteers are thanked for their assistance with photo and video sorting and processing. We thank the anonymous reviewers who helped improving this manuscript.

Funding information

The Norman Wettenhall Foundation contributed funds towards a white shark photo-identification catalogue.

Compliance with ethical standards

Ethical approval

AF owns a cage-diving licence and business at the study sites which enabled the photographs to be collected. The study conformed with the Australian code for the care and use of animals for scientific purposes.

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

265_2019_2745_MOESM1_ESM.docx (26 kb)
ESM 1 (DOCX 25 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.College of Science and EngineeringFlinders UniversityBedford ParkAustralia
  2. 2.UMR MARBEC (IRD, Ifremer Univ. Montpellier, CNRS)SèteFrance
  3. 3.Fox Shark Research FoundationAdelaideAustralia
  4. 4.Department of Biological SciencesMacquarie UniversityNorth RydeAustralia

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