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Encounters between white sharks and Cape fur seals in a shallow channel

Published online by Cambridge University Press:  10 March 2009

R. Johnson ,
T. Keswick ,
M.N. Bester  and
W.H. Oosthuizen
R. Johnson*
Affiliation:
Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria 0002, South Africa
T. Keswick
Affiliation:
Department of Zoology, University of the Western Cape, Private Bag X17, Belville 7535, South Africa
M.N. Bester
Affiliation:
Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria 0002, South Africa
W.H. Oosthuizen
Affiliation:
Branch Marine and Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Roggebaai, South Africa
*
Correspondence should be addressed to: R. Johnson, Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria 0002, South Africa email: info@sampla.org
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Abstract

This communication presents observations of predatory and non-predatory encounters between white sharks and Cape fur seals in a shallow (3–6 m) channel between Geyser Rock and Dyer Island, South Africa. Within the channel Cape fur seals raft extensively for thermo-regulatory purposes, to play, or due to terrestrial competition for space. The channel's physical environment effectively limits a white shark's approach orientation to the horizontal plane, thus inhibiting it to effectively utilize depth, and associated stealth, to capture pinnipeds. In the absence of effective camouflage, sharks may patrol this area in search of unaware, incapacitated or dead seals. Here, predator mobbing is a behavioural strategy adopted by Cape fur seals to lower predation risk. Specific benefits of mobbing may include: (a) perception advertisement to sharks; (b) intra-specific communication of a shark's locality; (c) driving the shark away from the area; (d) increased vigilance; (e) advertisement of a mobber's good health to a shark; and (f) possibly learning about a predator's behavioural capabilities by inexperienced prey. Mobbing expression is further promoted by the channel's shallow nature which enhances a seal's ability to visually detect the shark, and therefore makes it easier for a seal to evade it (reducing immediate predation risk). This environment thus promotes the widespread use of mobbing amongst Cape fur seals when confronted with a patrolling white shark.

Keywords

white sharkCape fur sealmobbingpredation
Type
Research Article
Information
Marine Biodiversity Records , Volume 2 , January 2009 , e52
Copyright
Copyright © Marine Biological Association of the United Kingdom 2009

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References

REFERENCES

Ainley, D.G., Henderson, R.P., Huber, H.R., Boekelheide, R.J., Allen, S.G. and McElroy, T.L. (1985) Dynamics of white shark/pinniped interactions in the Gulf of the Farallones. Memoirs of the Southern California Academy of Sciences 9, 109–122.Google Scholar
Anderson, S.D., Klimley, A.P., Pyle, P. and Henderson, R.P. (1996) Tidal height and white shark predation at the Farallon islands, California. In Klimley, A.P. and Ainley, D.G. (eds) The biology of Carcharodon carcharias. San Diego, California: Academic Press, pp. 275–279.Google Scholar
Barlow, G.W. (1972) A paternal role for bulls of the Galapagos Island's sea lion. Evolution 26, 307–308.CrossRefGoogle ScholarPubMed
Barlow, G.W. (1974) Galapagos sea lions are paternal. Evolution 28, 476–478.CrossRefGoogle ScholarPubMed
Cliff, G., Elst, R.P. van der, Govender, A., Witthuhn, T. and Bullen, E.M. (1996) First estimates of mortality and population size of white sharks on the South African coast. In Klimley, A.P. and Ainley, D.G. (eds) The biology of Carcharodon carcharias. San Diego, California: Academic Press, pp. 393–400.Google Scholar
Flasskamp, A. (1994) The adaptive significance of avian mobbing. V. An experimental test on the ‘Move On’ hypothesis. Ethology 96, 322–333.CrossRefGoogle Scholar
Frankenberg, E. (1981) The adaptive significance of avian mobbing. IV. ‘Alerting others’ and ‘Perception advertisements’ in blackbirds facing owls. Zeitschrift für Tierpsychologie 55, 97–118.CrossRefGoogle Scholar
Hamilton, W.D. (1964) The genetic evolution of social behaviour. Journal of Theoretical Biology 7, 1–52.CrossRefGoogle Scholar
Johnson, R.L. (2003) The behavioural ecology of the white shark (Carcharodon carcharias) at Dyer Island, South Africa. MSc thesis, University of Pretoria, Pretoria, South Africa.Google Scholar
Kirwood, R. and Dickie, J. (2005) Mobbing of a great white shark (Carcharodon carcharias) by adult male Australian fur seals (Arctocephalus pusillus doriferus.) Marine Mammal Science 21, 336–339.CrossRefGoogle Scholar
Klimley, A.P., Anderson, S.D., Pyle, P. and Henderson, R.P. (1992) Spatiotemporal patterns of white shark (Carcharodon carcharias) predation at the South Farallon Islands, California. Copeia 1992, 680–690.CrossRefGoogle Scholar
Klimley, A.P., Pyle, P. and Anderson, S.D. (1996) The behaviour of the white shark and their pinniped prey during predatory attacks. In Klimley, A.P. and Ainley, D.G. (eds) The biology of Carcharodon carcharias. San Diego, California: Academic Press, pp. 175–191.Google Scholar
Kock, A. and Johnson, R. (2006) White shark abundance: not a causative factor in the numbers of shark bite incidents. In Nel, D.C. and Peschak, T.P. (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 – 2006/Marine/001, pp. 1–19.Google Scholar
Martin, R.A., Hammerschlag, N., Collier, R.S. and Fallows, C. (2005) Predatory behaviour of white sharks (Carcharodon carcharias) at Seal Island, South Africa. Journal of the Marine Biological Association of the United Kingdom 85, 1121–1135.CrossRefGoogle Scholar
Miller, E.H. (1974) A paternal role in Galapagos Sea Lions. Evolution 28, 473–476.CrossRefGoogle ScholarPubMed
Ostreiher, R. (2003) Is mobbing altruistic or selfish behaviour? Animal Behaviour 66, 145–149.CrossRefGoogle Scholar
Pyle, P., Klimley, A.P., Anderson, S.D. and Henderson, R.P. (1996) Environmental factors affecting the occurrence and behaviour of white sharks at the Farallon Islands. In Klimley, A.P. and Ainley, D.G. (eds) The biology of Carcharodon carcharias. San Diego, California: Academic Press, pp. 281–291.Google Scholar
Rand, R.W. (1956) The Cape fur seal Arctocephalus pusillus (Shreber). Its general characteristics and moult. Investigational Report Division of Sea Fisheries, South Africa 21, 1–52.Google Scholar
Rand, R.W. (1967) The Cape fur seal (Arctocephalus pusillus pusillus). 3. General behaviour on land and at sea. Investigational Report Division of Sea Fisheries, South Africa 60, 1–39.Google Scholar
Stewardson, C.L. and Brett, M. (2000) Aggressive behaviour of an adult male Cape fur seal (Arctocephalus pusillus pusillus) towards a great white shark (Carcharodon carcharias). African Zoology 35, 147–150.CrossRefGoogle Scholar
Strong, W.R. (1996) Shape discrimination and visual predatory tactics in white sharks. In Klimley, A.P. and Ainley, D.G. (eds) The biology of Carcharodon carcharias. San Diego, California: Academic Press, pp. 229–249.Google Scholar
Tamura, N. (1989) Snake-directed mobbing by the Formosan Squirrel Callosciurys erythraeus thaiwanensis. Behaviour, Ecology and Sociobiology 24, 175–180.CrossRefGoogle Scholar
Zahavi, A. and Zahavi, A. (1997) The handicap principle. New York: Oxford University Press.CrossRefGoogle Scholar