How solitary are white sharks: social interactions or just spatial proximity?
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White sharks (Carcharodon carcharias) are circumglobally distributed large apex predators. While ecologically important, there is very limited study of their social behaviour. Although evident in other large, apex marine predators (e.g. toothed whales) and smaller elasmobranchs (e.g. blacktip reef sharks), the ability of any large pelagic elasmobranch to demonstrate social preferences, tolerance or grouping behaviour is largely unknown. Here, we test whether white sharks in a near-coastal environment form non-random associations with other conspecifics or simply share the same space at the same time. We photo-identified 323 individuals—74 % juvenile females (175–300 cm)—during chumming events at six different sites in Mossel Bay, South Africa, over a 6-year period (2008–2013), and tested for grouping behaviour. We found evidence for random associations among individuals, though spatio-temporal co-occurrence of white sharks in close proximity was weakly structured according to sex and, potentially, body size. Such biological traits may play a minor part in structuring co-occurrence of individuals at fine spatio-temporal scales, which could reflect ontogenetic preferences in diet and site fidelity, or differing tolerance levels for conspecifics of different sexes and sizes. Our study strengthens the evidence that large pelagic shark species are generally solitary and display limited social behaviour.
Large pelagic shark species are important top predators, but we know little about their social behaviour. We tested the ability of white sharks (C. carcharias) to form groups and display social preferences for other individuals when they congregate at scavenging events in a coastal environment, where social interactions may be more likely. We found that white sharks co-occur at random, displaying no preferred or avoided associations for other individuals. Nevertheless, there was a minor influence of biological traits, with individuals aggregating according to gender and, possibly, body size. While we hypothesise these effects could represent preferences in diet and site fidelity, or more tolerance for similar-sized individuals of the same sex, our study strengthens the evidence that white sharks are mostly solitary foragers.
KeywordsCarcharodon carcharias Association Social network Group Aggregation Tolerance
We thank Hal Whitehead for the help and advice on terminology, Lauren Peel for database management, all the volunteers and field specialists at Oceans Research for assistance during fieldwork and the two anonymous reviewers whose thoughtful comments improved our work.
RF was supported by Dalhousie University and Oceans Research; EG by Oceans Research, MC by doctoral scholarships from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq , Brazil) and Killam Trusts (Canada); and DT was supported by UNEP-WCMC.
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
- Cliff G, Van Der Elst RP, Govender A, Witthuhn TK, Bullen EM (1996) First estimates of mortality and population size of white sharks on the South African coast. In: Klimley AP, Ainley DG (eds) Great white sharks: the biology of Carcharodon carcharias. Academic Press, London, pp. 393–400CrossRefGoogle Scholar
- Compagno LJV (2002) Sharks of the world: an annotated and illustrated catalogue of shark species known to date, Vol. 2. Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes). Food and Agriculture Organization of the United Nations, RomeGoogle Scholar
- Curtis TH, Kelly JT, Menard KL, Laroche RK, Jones RE, Klimley AP (2006) Observations on the behavior of white sharks scavenging from a whale carcass at Point Reyes, California. Calif Fish Game 92:113–124Google Scholar
- Dudley SFJ, Anderson-reade MD, Thompson GS, McMullen PB (2000) Concurrent scavenging off a whale carcass by great white sharks, Carcharodon carcharias, and tiger sharks, Galeocerdo cuvier. Fish Bull 649:646–649Google Scholar
- Estrada JA, Rice AN, Natanson LJ, Skomal GB (2014) Use of isotopic analysis of vertebrae in reconstructing ontogenetic feeding ecology in white sharks. Ecol Soc Am 87:829–834Google Scholar
- Ford B, Ellis M, Balcomb C (2000) Killer whales: the natural history and genealogy of Orcinus orca in British Columbia and Washington. University of Washington Press, SeattleGoogle Scholar
- Hamady LL (2014) Age, movement, and feeding ecology of Northwest Atlantic white sharks estimated from ecogeochemical profiles in vertebrae. Dissertation, Massachusetts Institute of Technology and Woods Hole Oceanographic InstitutionGoogle Scholar
- Hewitt AM (2014) Demographics of a seasonal aggregation of white sharks at Seal Island, False Bay, South Africa. Dissertation, University of Cape TownGoogle Scholar
- Johnson R, Kock A (2006) South Africa’s white shark cage-diving industry—is there cause for concern? In: Nel DC, Peschak TP (eds). Finding a balance: white shark conservation and recreational safety in the inshore waters of Cape Town, South Africa; proceedings of a specialist workshop. WWF South Africa Report Series, South Africa, pp 40–59Google Scholar
- Kime DE, Hews EA (1982) The effect of temperature on steroid biosynthesis by testes of the dogfish, Scyliorhinus caniculus. Comparative biochemistry and physiology. Biochem Mol Biol 4:675–679Google Scholar
- Krause J, Ruxton G (2002) Living in groups. Oxford University Press, OxfordGoogle Scholar
- Lee KA, Huveneers C, Gimenez O, Peddemors V, Harcourt RG (2014) To catch or to sight? A comparison of demographic parameter estimates obtained from mark-recapture and mark-resight models. Biodivers Conserv 23:2781–2800Google Scholar
- Whitehead H (2003) Sperm whale societies: social evolution in the ocean. University of Chicago Press, ChicagoGoogle Scholar
- Whitehead H (2009) SOCPROG programs: analysing animal social structures. Behav Ecol Sociobiol 63:765–78Google Scholar