Knowing sharks as social beings

Alongside the conventionally cuddly toy kangaroos, koalas and wombats that have long been sold in the Taronga Zoo gift shop in Sydney, Australia, a newcomer stands out: a fuzzy plush shark. It’s bait for young visitors, of course, but it’s also a symbol of efforts to explore the softer side of these widely feared animals. In 2015, the zoo unveiled an exhibit featuring a small group of Port Jackson sharks, a joint project with Macquarie University, where researchers are studying the social behaviour of sharks to help battle the misconception that sharks are largely solitary creatures.

The secondary goal of the project is to elevate sharks’ social standing among humans — a concern that is particularly relevant in Australia, where shark attacks are often the subject of sensational headlines and there are frequent calls for culling, despite the fact that fatal attacks happen only once a year on average in the country. “More people die from falling off cliffs while taking selfies than from shark attacks,” said Culum Brown, an assistant professor at the Behaviour, Ecology and Evolution of Fishes Laboratory at Macquarie, citing an apparently well-documented global statistic.

Not a solitary animal
The project began four years ago after one of Culum’s students proposed investigating whether sharks engage in the same kind of social behaviours as humans — like gathering together for the pure pleasure of company, for instance. While some species of sharks, like hammerheads, are known to form large schools, there has been little research that looks at why: Is it a social thing, or are the sharks simply attracted to a particular resource?
“The general feeling is that sharks are robots — that they’re anti-social and they go around munching and killing things,” Culum said. “Nobody knows about the social lives of sharks because it’s notoriously hard to track them.” Culum assembled a team of students and volunteers and spent three months at Jervis Bay, on the New South Wales coast, 90 miles south of Sydney, searching the waters for research subjects. Port Jackson sharks seemed to fit the bill — at about 5 feet long, they are big enough to spot in the water and they are plentiful. “They are probably the most common shark in Australian waters and are relatively friendly,” Culum said. “If you grab them, they tend to be passive.”

They tagged and released the sharks, using a combination of tracking tools. Passive integrated transponder (PIT), tags, slightly larger than a grain of rice, hold electronics that allow them to act as lifelong bar codes that can be detected and read without the animal having to be recaptured. The tags were inserted into each shark via a small incision on the animal’s underside.

An acoustic tag attached to the fin of each shark sends out a ping each time it comes within about a third of a mile of an underwater receiver, or within about 30 feet of another tagged shark. Each ping is time-stamped, meaning it is possible to detect when a particular shark was at a particular location, and whether it came into contact with any other tagged sharks.

During the initial tagging process, Culum’s team tagged 250 sharks in Jervis Bay with both PIT and acoustic tags. Last year, 38 more were tagged. From the data analysed so far, Culum found that the Port Jackson sharks tagged four years ago consistently returned to some locations. At first, it was thought they were coming together to breed but Culum later discovered the sharks were of mixed ages and sexes, leading to another theory: sharks liked to dine together.

To rule out the possibility that the animals were attracted to the location itself rather than one another, Culum needed an artificial environment in which to observe them up close. So he reached out to a former student, Jo Day, who had studied social interactions in bottlenose dolphins and now worked as a research and conservation coordinator at Taronga Zoo. While Jo was enthusiastic about the possibility of creating a shark habitat there, zoo officials took some convincing — the zoo hadn’t had a shark exhibit for 25 years.

Eradicating the fear
In September 2015, Culum brought in 10 sharks, which immediately took to their new home — a pool 60 feet long, 10 feet deep and 23 feet wide, embellished with a waterfall and rock shelters at the bottom to replicate the kinds of spots where Port Jackson sharks gather in the wild. While the data has yet to be formally analysed, early observations back the hypothesis that the sharks like being around one another. “Instead of being spread out around the pool, they are always together,” Culum said. “We’ve seen this in the wild, too, but here, there’s no reason they’d be attracted to anything in the shelter, because it’s all artificial.”

In addition to the PIT and acoustic tags, the sharks in the pool had accelerometers attached to their dorsal fins, to measure their movement patterns in three dimensions. Three cameras were set up around the underwater viewing area, recording where the sharks swam and what they did. This allows the researchers to match the signature produced by each shark’s accelerometer to a particular behaviour: swimming, resting, eating or mating. Once a kind of template is established, it will be possible for Culum and his team to determine not just where the sharks go once they are released back in the wild, but also what they are doing.

These high-tech trappings helped make the shark experiment a hit for the zoo. “We always overhear kids saying things like, ‘Let’s go see the sharks!’” Jo said. “One keeper talk on the exhibit drew a crowd of around 100 people. It’s one of the most popular exhibits at the zoo.” The response also pleases Culum. “The fear of sharks is an irrational one,” he said. “It’s hard to get over an irrational fear. But we’re trying to teach people that sharks aren’t mindless killing machines, that sharks are interesting and do interesting things. Most sharks are under threat from us, not the other way around.”