by Mike Gaworecki, Mongabay.com (Photo via Wikimedia Commons.)
Personality in humans defines who we are. It is the unique combination of qualities and traits that form our distinct characters as individuals.
Many people don’t tend to think of animals as having personalities — when they think of “elephants,” they are probably thinking of the species as a whole or in the abstract rather than thinking of the species as a collection of individuals. But research is proving that animals do in fact have personalities in very much the same way we would define it for humans.
A team of researchers from Macquarie University in Australia who observed the behavior of sharks off the east coast of Australia, for instance, found that individual sharks had distinct and consistent responses when exposed to an unfamiliar environment or stressor. This stable set of behaviors, they say, shows that each of the animals have personalities all their own.
“Over the past few decades, personality research has shown that nearly 200 species of animals demonstrate individual personality,” Macquarie’s Evan Byrnes, the lead author of the study, published in the Journal of Fish Biology this month, said in a statement. “Personality is no longer considered a strictly human characteristic, rather it is a characteristic deeply engrained in our evolutionary past.”
Documenting animal personality is a new frontier in behavioral ecology studies, and so far “personalities” have been demonstrated to exist in various species of amphibians, birds, fishes, insects, mammals, molluscs — and now sharks.
Byrnes and team studied the “boldness” of Port Jackson sharks (Heterodontus portusjacksoni), a type of bullhead shark found off the coast of Australia, including in Port Jackson, on Australia’s southeast coast. Their study measured the sharks’ proclivity to taking risks when confronted with different situations in order to determine whether or not individual sharks respond in a similar manner to a variety of stimuli.
The sharks were first introduced to a tank equipped with a shelter, then timed to see how long it took for each of them to emerge from the hiding spot into their new environment. The second behavioral test involved exposing each shark to a stressful situation similar to being handled by a fisherman before releasing them and observing how quickly they recovered.
Byrnes and team say that each individual shark’s behavior was consistent over four repeated trials, indicating ingrained behavioral patterns rather than capricious or random reactions. Some sharks were reliably bolder than others, they found, and those sharks that reacted most strongly to the stress of being handled repeated that response across the multiple tests.
“We are excited about these results because they demonstrate that sharks are not just mindless machines,” Macquarie University professor Culum Brown, a co-author of the study, said in a statement. “Just like humans, each shark is an individual with its unique preferences and behaviours.”
Brown added that these results raise a number of questions about individual variation in the behavior of top predators and the ecological and management implications those behaviors may have.
“Personality is a dimension of animal psychology that influences evolutionarily and ecologically important behaviours of wild individuals and populations,” the authors write in the study. “Personality traits can influence individual factors such as diet preference and habitat use, and different combinations of traits within a population can variably influence ecosystem dynamics.”
In other words, every shark is an individual “doing its own thing,” Brown said, which means that properly managing shark populations is a far more complicated task than we previously thought.
“Understanding how personality influences variation in shark behaviour — such as prey choice, habitat use and activity levels — is critical to better managing these top predators that play important ecological roles in marine ecosystems.”