A tourist looks up through a glass tunnel at a group of Port Jackson sharks resting in the Sydney Aquarium August 5, 2003. Reuters/David Gray

Sharks may be responsible for numerous attacks on beachgoers and swimmers, but new research has revealed that not all sharks are mindless killers even if they seem to be. In fact, sharks are not mindless killers at all. According to Macquarie University scientists, sharks have distinct personalities and there are risk-taking sharks, shy sharks and also highly strung sharks that find stress difficult to handle. Just like humans, they have distinct individual personalities.

According to the study, published in the Journal of Fish Biology on Thursday, smaller sharks tend to be very shy mainly because they are more vulnerable to predators. Interestingly, personality differences were not found between the sexes. The results of the study that carried out the first “personality test” of wild sharks showed that the predators are individuals with their own distinct way of reacting to unfamiliar environments and stress.

“It's been a 10 to 15-year struggle to even get scientists to accept that animals have personalities. And this shows that sharks are far from mindless killers,” Macquarie University behavioural ecologist and associate professor Culum Brown told The Sydney Morning Herald.

Brown added that his team was surprised to find the lack of personality differences between sexes because “males tend to be bolder than females in just about every animal that has ever been looked at.” However, he also said that this could have been due to the small sample size. The study involved seventeen wild Port Jackson sharks from eastern Australia.

The reason why the researchers chose this species of sharks is because they are easily available and their size is easier to work with. Larger species of sharks would have made it difficult for the scientists to handle. Port Jackson sharks weigh up to 30 kilograms and are about 1.5 metres long. Moreover, these sharks, unlike other species, do not grip and rip their prey’s flesh. Instead, they crush the shells of their crustacean prey. Their teeth are not razor-sharp but are designed to crush.

The researchers tested the sharks on traits such as boldness and resilience to stress. From the evolutionary perspective, sharks are ancient creatures and their personality traits go back to the beginning of the vertebrates some 300 million years ago. The findings suggested that management of wild and captive sharks must take into account their responses to stressful situations.