For the first time ever, a team of researchers from Macquarie University has discovered evidence of individual personality differences in Port Jackson sharks from the east coast of Australia. The study reveals that the sharks in the study exhibited distinct and consistent responses in the face of an unfamiliar environment and stress.
In human psychology, our personality is believed to make up who we are and can be used to determine how we respond to certain situations, allowing for behavioral prediction. This stems from the fact that our behavior tends to remain consistent and repeat over time, and it is this predictability to makes up the foundation of personality.
"Over the past few decades, personality research has shown that nearly 200 species of animals demonstrate individual personality," said Evan Byrnes of Macquarie University and lead author of the study. "Personality is no longer considered a strictly human characteristic, rather it is a characteristic deeply engrained in our evolutionary past."
The team set out to determine if sharks possess personalities by putting them through trials to test their boldness, which not only measures their propensity to take risks but also influences individual health due to its connection to stress hormones and physiological profiles.
The team introduced the sharks to a tank that provided shelter and determined how long it took them to emerge from this shelter into the new environment. Afterwards, they exposed the sharks to handling stress and then released them again and determined their recovery time.
The results revealed that each shark possessed behavior that was consistent over each trail and suggests that these behaviors are ingrained as opposed to being spontaneous reactions. For example, some sharks were consistently bolder than others, and those that were most reactive to handling stress during the first trial were most reactive in the second as well.
"We are excited about these results because they demonstrate that sharks are not just mindless machines," said Culum Brown of Macquarie University and senior author of the study. "Just like humans, each shark is an individual with its unique preferences and behaviors."
"Our results raise a number of questions about individual variation in the behavior of top predators and the ecological and management implications this may have," he added. "If each shark is an individual and doing its own thing, then clearly managing shark populations is much more complicated than we previously thought."
The findings were published in the May 26 issue of the Journal of Fish Biology.