An Emerging Picture of White Shark Predatory and Social Behavior at Seal Island

The White Shark ( Carcharodon carcharias ) is a marvel of biological engineering. A large adult may be as much as 2.5 tons of cartilage and muscle, guts and gills, nerves and blood vessels, sense organs and brain, all organized into smoothly functioning wholeness. The relentless processes of evolution have sculpted the White Shark's body form and life history over hundreds of millions of years. The result is a creature superbly adapted to swim, feed, and breed in the largest interconnected habitat on our planet. The White Shark is the largest predatory fish on our planet; however the natural history, feeding biology, distribution and ecology of this magnificent predator remain virtually unknown.

Research now being conducted at Seal Island, in False Bay, South Africa is providing new insights into the biology and behaviour of the White Shark. Seal Island provides an exceptional opportunity to study the natural hunting and social behaviour of this celebrated predator. South African naturalists Chris Fallows and Rob Lawrence began working at the site in 1996, establishing field methodology and recording their observations. Fallows and Lawrence were subsequently joined by biologists from the ReefQuest Centre for Shark Research, including R. Aidan Martin and Neil Hammerschlag. Between 1996 and 2004, their team documented 2,500 natural predations and identified 300 individual sharks. Their accumulated data is revealing aspects of the mental processes, predatory strategies, and social hierarchy of one of our planet's most feared and least understood creatures. An overview of their on-going research and preliminary results is presented below:

During the winter, White Sharks visit Seal Island to predate on Cape Fur Seals (Arctocephalus pusillus pusillus) . About 47 % of surface attacks on Cape Fur Seals result in successful kills. Attack frequency is high, averaging 5.6 per day, with as many as 35 recorded in a single day. Sharks attack seals on the surface via a sudden vertical rush, which propels predator and prey out of the water in an awesome display of power and acrobatic prowess. White Sharks appear to hunt solitary juvenile Cape fur seals near their primary entry and exit point early in the morning, when light levels are low. Stalking is conducted from near the bottom, from sufficient depth to remain undetected during approach, and the attack launched vertically, which maximizes a shark's chance of catching a seal unaware, resulting in a fatal initial strike. Stealth and ambush are key elements in the White Shark's predatory strategy. Further, recognizable individual White Sharks display distinct predatory strategies and some enjoy a predatory success rate of roughly 80%.

Some 300 individual White Sharks have been catalogued to date, including numerous re-sightings over separate days and years. Accumulated data is beginning to show that White Sharks at Seal Island stay for only a few days at a time, many of the same individual sharks return year after year, and that numerous identifiable sharks appear to come and go together in groups of two to six. Group constitution appears to be constant from year-to-year and threat interactions among group members is low (suggesting well-established, stable social hierarchies), but occurs occasionally between members of different groups. Social hierarchies are stabilized and maintained largely through discrete behaviours, ranging from subtly synchronized swimming to overt displays.

Although a picture of White Shark predatory and social behaviour at Seal Island is emerging from these on-going studies, much remains unknown about the biology of these creatures and more efforts are needed to conserve White Sharks. In 1991, South Africa became the first nation to declare the White Shark fully protected in its waters. However, they continue to be captured illegally at Seal Island and elsewhere along South Africa's coast, where they are caught for sport as well as for their jaws, teeth, and fins, which fetch high prices. Moreover, their habitats are being degraded due to industrial growth and their food supplies are vanishing to support our rapidly growing populations. Every mature White Shark removed from the environment represents a significant loss that likely has dramatic repercussions throughout its ecosystem.

In contrast to previous decades, the White Shark now has legions of fans who regard our world as richer for including such a charismatic and mysterious creature. Increasing numbers of people are coming to appreciate that the White Shark is a rare wild animal that adds to the richness, diversity, myth, and mystery of our world. The movement to increase protection for the White Shark in South Africa and around the world is growing, so there remains hope. The Seal Island research team urges fellow shark enthusiasts to actively support White Shark conservation by boycotting the sale of its jaws, teeth, and fins and encouraging others to do the same. With your help, the White Shark will survive to awe, amaze, and inspire people for many generations to come.