Weipa is a small coastal mining town in Queensland, located in northeastern Australia, particularly favored by sports fishermen because of its annual competition, the Weipa Fishing Classic. But in recent years, fishermen have reported an increasing number of incidents where local bull sharks are pulling off audacious underwater raids, literally waiting until a fish is hooked and chomping it off the line. Some fishermen estimate they can lose as much as 70 percent of their catch to the sharks, which seem to specifically target fishing boats.
(Some spoilers for the documentary below the gallery.)
It’s atypical behavior for bull sharks, and it raises an interesting question: Is this evidence that this species of shark—known (a bit unfairly) in the popular imagination for being aggressive “mindless killers”—is more intelligent than previously assumed? That’s one of the questions that shark biologists Johan Gustafson and Mariel Familiar Lopez set out to answer, and their initial field work has been documented for posterity in Bull Shark Bandits, part of National Geographic’s 2023 SHARKFEST programming. SHARKFEST is four full weeks of “explosive, hair-raising and celebratory shark programming that … showcase the captivating science, power and beauty of these magnificent animals,” per the official description.
The fish-stealing behavior is technically known as depredation. Among other factors, Australian fish stocks have decreased by more than 30 percent over the last decade, and the sharks appear to be adapting accordingly and teaching the behavior to their fellow sharks.
“Many different species do it, including dolphins and orcas, high-level predators, but shark depredation in particular is occurring all over Australia at the moment,” Gustafson told Ars. “In areas where there’s a higher fishing pressure, the behavior is occurring more often or more intensely. We call it habituation. They’ve learned a habit, they actually learn off each other, and they spread it around [the population].”
Bull sharks (Carcharhinus leucas) are found all over the world, usually preferring warm, shallow coastal waters and freshwater rivers. They’re not a true freshwater species, but the females typically birth their pups upriver since such spots provide a more protective environment for nurseries. (Sharks don’t rear their young; baby sharks typically join the adult ocean population when they reach about eight years of age.) Bull sharks usually grow to an average of 7 feet (for males) and 8 feet long (for females), and their powerful bite can generate as much as 1,330 pounds of force (5,914 newtons).
Bull sharks are considered opportunistic feeders, meaning they eat in short bursts and digest for longer periods during times of scarcity. Their diet favors bony fish and smaller sharks (including their fellow bull sharks), as well as turtles, birds, dolphins and crustaceans. They’re also fairly territorial and solitary, preferring to hunt alone or occasionally in pairs.
Their reputation for aggression has been fueled in part by media reports of bull shark attacks, including the 1916 Jersey Shore shark attacks that inspired Jaws—both the novel by Peter Benchley and the 1975 blockbuster film (although both actually featured a Great White shark). Bull sharks are indeed responsible for many shark attacks near coastal shores, and they have a ferocious bite. But the reality is more nuanced. “I always tell people that every animal, every human or every dog, we all have different personalities,” Lopez told Ars. “So you might get a bull shark that is really aggressive, but you might get one that is not. Their main focus is always catching meals. But they’re not, like, ‘Oh, I’m going to be aggressive to every single thing that I see.'”