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
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.