Shark Researcher Explains Great White Behaviour

July 12, 2004

Release from: Helena Webb
ABC (Australia)

Following the death of a surfer at a popular spot in Western Australia's south west, CSIRO scientest Barry Bruce sorts fact from myth about the great white's behaviour.

Since 1803, 11 shark attacks have been recorded in Western Australian waters. Shark attack, says CSIRO reseacher Barry Bruce is an unlikely unevent. But he adds, the statistics don't take away from the tragedy when people are killed by sharks. When attacks happen, people are always searching for answers, Barry feels, that aren't necessarily there. Sharks, he says, are "highly complex animals with complex behaviours."

One of the most often asked question about sharks is why do they attack humans. "We really don't know," says Barry. There are many hypotheses from mistaken identity to territoriality. Sharks could simply be hunting in the area and come across people. As to whether or not a shark would be more likely repeat the behaviour, having attacked a person, Barry feels that "there's really no evidence to suggest that any shark having bitten a person, is any more likely or less likely to do so again."

Nor are the sharks involved in the attack likely to be found, he believes. Sharks move at around 3km/hr and move along directed lines, he tells us in the interview. The usually move away from an area after an event such as this. Two days after the attack at Gracetown, the sharks could be 150km away. "The chances of finding the sharks responsible or even identifying the sharks responsible, diminishes quite incredibly." But while he doesn't believe that we would be making the seas a safer place by shooting these animals, if they could be found, Barry understands that people might want revenge or perhaps closure following an attack. Sharks are not mindless killing machines

A senior reseach scientist for Marine Reseach at the Commonwealth Scientific and Industrial Reseach Organisation, Barry Bruce has been studying the great white shark since 1987. Great whites are an endangered species and results from the CSIRO project will contribute to a national recovery plan. The reseach team tags and tracks the sharks wherever possible, but it's not easy. Sharks are both difficult and expensive to find. Another source of information is biological data such as age and growth which can be ascertained from sharks caught in fishing nets. Great whites are in the same family as mako sharks. They're warm bodied creatures, maintaining their body temperature higher that the surrounding water and that makes them more efficient swimmers and predators in colder waters, says Barry. They occur between southern Australia and Hawaii but are more common down south.

Sharks "move into shallow waters as part of their normal hunting strategy," says Barry. Tracking studies so far have shown that sometimes quite large sharks can be in water just a couple of metres deep. This is regular, but "not necessarily frequent." Sharks can also travel together, though this is not necessarily school behaviour where fish move and change direction as one. The sharks might simply be following the same cues, following a seal colony or perhaps travelling to the next likely meal. At Gracetown, two sharks were reported as taking part in the fatal attack. While sharks can sometimes feed together, Barry warns against reading proximity as cooperative behaviour. "Sharks are not mindless killing machines as we have been led to believe," he says. "They are highly evolved predators. They don't hunt for fun. There's no need for them to kill ten seals at a seal colony. They won't go round biting everything in their path."