Research

The Great White Shark - often misunderstood and in need of help!

Since 2000, we have been working with R. Aidan Martin of the ReefQuest Centre for Shark Research and small groups of selected volunteers to study the predatory behaviour, residency patterns, and social organization of Great White Sharks at Seal Island.

Shark attacks

Our group of researchers have documented over 2500 natural predatory interactions between Great White Sharks and Cape Fur Seals at Seal Island, with an average of 6.7 attacks per day and up to 43 attacks observed in a single day.

Attacks are clustered at the primary seal entry/exit point at the south end of the Island and occur almost exclusively during winter months (May-September). We have discovered that predatory behaviour of Great White sharks is more complex than traditionally thought.

They selectively target young, inexperienced seals returning to the rookery alone and exhibit a repertoire of at least 20 different predatory behaviours. Seal concentration and predation frequency peak close to Seal Island, yet predatory success rate is lowest where competition among White Sharks is most intense and highest where competition is lowest.

This is the first time anyone has demonstrated a link between social factors and feeding success in any shark. We have documented as many as 34 individual White Sharks at Seal Island in a single day. Due to the high degree of competition among sharks, successful predations typically last less than one minute, consisting of a single breach, secondary lunge and final lateral snap of the jaws.

Shark predation

Predation frequency peaks within one hour of sunrise; about 90 minutes later, the success rate falls to around 40% and the sharks appear to cease active predation -- a phenomenon that has not been previously demonstrated in any predatory fish. We have also discovered that White Sharks learn to become better killers.

Larger sharks tend to attack seals farther from shore and enjoy higher success rates than smaller individuals, which may not have learned the best places to hunt. Idiosyncratic predatory strategies and elevated success rates of recognised individuals further suggest that some degree of trial-and-error learning is involved.

Using total pigmentation pattern, analysed according to 68 discrete body regions, 262 individual White Sharks have been catalogued to date and their residency patterns and associations with other White Sharks are revealed by re-sightings data.

Catalogued individuals have been re-sighted as often as 28 times over the years, suggesting a high degree of site fidelity. Residence times for individual Great White Sharks at Seal Island range from 1-18 days, averaging 2-3 days. Known individuals appear to travel in loose groups of two to six individuals. We have documented 17 distinct social behaviours among White Sharks at Seal Island, but agonistic (threat) behaviours appear to occur only between individuals of separate groups.

Social hierarchy of Great White Sharks under baited conditions appears to be largely size-dependent, with individuals as little as 5% longer dominant over smaller members of the same species, but sex and relative degree of pigmentation may also be factors.

Our research has been featured in numerous television documentaries and the results of our studies have been presented at international scientific conferences and technical reports have been published in professional journals. If you would like to participate in this research, apply on-line at www.reefquest.com and let us know why you would be a valuable addition to our Research Team.

Please take the time to read through our Great White Shark Research notes:

Predatory behaviour of Great White Sharks (2,073kb)
Happy Eddie (748kb)