Anti-Predatory Strategies of Cape Fur Seals at Seal Island

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Great Whites often sport numerous scratches on their heads, most likely caused by seals defending themselves during predatory events
Great Whites often sport numerous scratches on their heads, most likely caused by seals defending themselves during predatory events.

From direct observation and data collected, Cape Fur Seals apparently reduce their vulnerability to Great White Sharks by:

  • taking advantage of the expanded vigilance of entire groups. Sub-surface vigilance while rafting is accomplished via assuming a head-down posture, with only the tail and the tip of the rear flippers showing above the surface.
  • leaving Seal Island as co-ordinated groups of 8 to 12 animals. Multiple groups – ranging from 2 to as many as 5 – leave the island at intervals of approximately 45 seconds.
  • single or small groups (2-5) of individuals executing a finely controlled zig-zaging evasive maneuver when a Great White Shark is spotted stalking below them. This tactic is referred to as “working the shark”.
  • when an individual is actively pursued by a Great White Shark, riding its slipstream – usually mid-body, at the level of its dorsal fin – to remain out of reach of the shark’s jaws; this tactic is referred to as “on the shark”
  • when a group is “hit” (attacked) by a White Shark, the individual seals ‘explode’ from the water in all directions, presumably serving to confuse the predator – perhaps sufficiently to allow some or all of them to escape. This tactic is relatively infrequent but highly spectacular.
  • when an individual or group returns to the island, swimming the last 50 metes or so underwater, presumably because this tactic reduces vulnerability to attack by Great White Sharks.
  • when any or all of the aforementioned tactics fail and a predatory attack is successful, the surviving seals become extremely vigilant – often to the point of seeming momentarily stunned – but are, in fact, hyper-alert.

In short, the Cape Fur Seal’s main anti-predatory strategies rely on vigilance and agility.

Join Rob Lawrence and the African Shark Eco-Charters team on one of our popular “Airjaws” trips to experience the anti-predatory strategies of the Cape Fur Seal against the Great White Shark first-hand.

Data collected and observations by R. Aiden Martin of the ReefQuest Centre for Shark Reasearch, as well as Rob Lawrence.

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