It’s crafty, fish-stealing sharks vs. anglers in NatGeo’s Bull Shark Bandits

Weipa is a small coastal mining city in Queensland, positioned in northeastern Australia, notably favored by sports activities fisherman due to its annual competitors, the Weipa Fishing Classic. But in current years, fishermen have reported an rising variety of incidents the place native bull sharks are pulling off audacious underwater raids, actually ready till a fish is hooked and chomping it off the road. Some fisherman estimate they’ll lose as a lot as 70 % of their catch to the sharks, which appear to particularly goal fishing boats.

(Some spoilers for the documentary beneath the gallery.)

It’s atypical habits for bull sharks and it raises an fascinating query: is that this proof that this species of shark—identified (a bit unfairly) in the favored creativeness for being aggressive “senseless killers”—are extra clever than beforehand assumed? That’s one of many questions that shark biologists Johan Gustafson and Mariel Familiar Lopez got down to reply, and their preliminary subject work has been documented for posterity in Bull Shark Bandits, a part of National Geographic’s 2023 SHARKFEST programming. SHARKFEST is 4 full weeks of “explosive, hair-raising and celebratory shark programming that … showcase the charming science, energy and wonder of those magnificent animals,” per the official description. 

The fish-stealing habits is technically referred to as depredation. Among different components, Australian fish shares have decreased by greater than 30 % over the past decade, and the sharks look like adapting accordingly and instructing the habits to their fellow sharks.

“Many totally different species do it, together with dolphins and orcas, excessive stage predators, however shark depredation in specific is happening throughout Australia for the time being,” Gustafson advised Ars. “In areas the place there is a greater fishing stress, the habits is happening extra typically or extra intensely. We name it habituation. They’ve realized a behavior, they really study off one another, and so they unfold it round [the population].”

Bull sharks (Carcharhinus leucas) are discovered all around the world, normally preferring heat, shallow, coastal waters and freshwater rivers. They’re not a real freshwater species, however the females sometimes beginning their pups upriver since such spots present a extra protecting surroundings for nurseries. (Sharks do not rear their younger; child sharks sometimes be a part of the grownup ocean inhabitants once they attain about eight years of age.) Bull sharks normally develop to a mean of seven ft (for males) and eight ft lengthy (for females), and their highly effective chunk can generate as a lot as 1330 kilos of pressure (5914 newtons).

Bull sharks are thought-about opportunistic feeders, which means they eat in brief burts and digest for longer durations throughout instances of shortage. Their eating regimen favors bony fish and smaller sharks (together with their fellow bull sharks), in addition to turtles, birds, dolphins and crustaceans. They’re additionally pretty territorial and solitary, preferring to hunt alone or sometimes in pairs.

Their repute for aggression has been fueled in half by media experiences of bull shark assaults, together with the 1916 Jersey Shore shark assaults that impressed Jaws—each the novel by Peter Benchley and the 1975 blockbuster movie (though each really featured a Great White shark). Bull sharks are certainly answerable for many shark assaults close to coastal shores, and so they have a ferocious chunk.  But the fact is extra nuanced. “I all the time inform individuals that each animal, each human or each canine, all of us have totally different personalities,” Lopez advised Ars. “So you may get a bull shark that’s actually aggressive, however you may get one that isn’t. Their principal focus is all the time catching meals. But they don’t seem to be, like, ‘Oh, I’m going to be aggressive to each single factor that I see.'”

It wasn’t completely clear from the varied accounts if it actually was bull sharks stealing the fish, because it all occurs underwater. So the primary order of enterprise for Gustafson and Lopez was to confirm the anecdotal experiences and attempt to catch a bull shark in the act. They used a fishing line digital camera to seize a low-resolution shot of a bull shark stealing a hooked fish in simply 20 seconds, however they wanted to get into the water to seize extra footage with a 360-degree drop digital camera. A shark cage was in order, however most metallic cages are pretty noisy in phrases of sound reflection. That’s positive with some regional sharks who’re used to the cages, per Gustafson, however the Weiba bull shark inhabitants is extra remoted and extra prone to be spooked by the noise.

So Gustafson and Lopez turned to underwater cinematographer Colin Thrupp, who constructed a novel noise-cancelling shark cage out of polyethylene pipe with the joints welded through electro-fusion welding. The plastic absorbs sound greater than a metallic cage, and the black coloration additionally means much less reflective shine. The cage served its objective; the bull sharks have been initially cautious however the digital camera finally caught six or seven of them swimming close by as a pack—uncommon habits for a such a solitary and territorial species. “Part of our speculation is that this can be a inhabitants of bull sharks that do not actually migrate that a lot, as a result of they have heat water circumstances all 12 months spherical, it is a good tropical space,” stated Lopez. “That is possibly one of many components [providing] alternative for socialization. They may be getting a little bit of toleration between one another as a result of they’re getting a straightforward meal.”

The footage additionally confirmed a bull shark approaching the hooked fish slowly at first, ready for it to get bored with struggling, after which biting off the fish’s tail finish and propeller, earlier than swinging again round to gulp down the remaining. This is a peaceful, clever searching technique, per Gustafson and Lopez, the antithesis of the stereotypical senseless aggression normally related to bull sharks. In truth, it is strikingly just like how killer whales—identified for his or her intelligence—hunt, using a surgically exact strategy to save lots of power. “Being a prime predator means you make investments loads of power in all these catches,” stated Lopez. “If that does not include a reward, you will have much less power for the subsequent chase. So they should be very clever [to determine] ‘Where do I put my power in all this?’ Sometimes, once they’re unsure, they do these check bites.”

The plastic cage did not carry out completely, nonetheless, beginning to bounce round and buckle as swells developed and underwater turbulence elevated. The communications hyperlink to the floor additionally went out, ensuing in some tense moments till the cage was introduced again to the floor.  “We have been in that cage and it was gloomy and the present was large,” Gustafson recalled. “Then we noticed a cable tie  fly previous us and thought, ‘Oh, that is not good,’ as a result of they’re really what’s holding the cage [mesh] collectively. Then one other one glided by. Then the cage began to deform. It was like being in a [trash] compactor.”

Gustafson and Lopez additionally managed to tag a number of sharks with acoustic transmitters to trace their actions. Since they’d noticed a juvenile shark among the many adults, additionally they  positioned the almost definitely bull shark nursery in a close-by river, taking a biopsy from one child shark for DNA evaluation. Once Thrupp had repaired and strengthened the plastic shark cage, they deployed it a second time to take biopsies of two different sharks for comparability, utilizing harpoon-like instruments.

The outcomes confirmed that the juvenile they biopsied upriver was half-related to the feminine bull shark they biopsied again in the ocean, whereas the third sampled shark was associated to each of them. So all three sharks possible share an ancenstor between them. This is but extra proof that the inhabitants at Weiba is not transferring round a lot, as a result of there may be extra alternative for interbreeding, notably since shark litters sometimes have a number of fathers, per Gustafson.

The subsequent step consists of gathering extra DNA samples from the Weiba bull shark inhabitants to increase the genetic evaluation, in addition to tagging and monitoring extra bull sharks to get a way of their motion patterns in order to find out how the highest finish of the gulf ecosystem (Weiba) connects to the western and jap sides of the continent. “Do they go all the best way all the way down to Perth on the west or proper all the way down to Sydney?” stated Gustafson. “Turtles have a tendency to come back again to the identical seaside the place they have been born. We assume these bull sharks are beginning to do the identical form of a factor. But we do not know in the event that they’re coming again to the identical river that they have been born in, or into the identical space that they have been born in.”

More knowledge must also give them a greater concept of the dimensions of the bull shark inhabitants in Weiba, because the fashionable notion amongst fishermen is that there should be lots of or hundreds of them. And as fishermen preserve shedding their catches, there’s a higher danger of extra anger being directed on the bull sharks, resulting in decreased help for his or her conservation and extra requires culling the inhabitants. (The species is listed as weak on the IUCN Red List.)

“The extra you spend time in the water, the likelihood that you’ll encounter a shark turns into higher,” stated Lopez. “But that’s simply since you’re spending extra time in the water fishing. It does not imply there are extra sharks lurking in the waters and being aggressive. It’s vital to do these documentaries since you’ll by no means change the thoughts of individuals in the event you simply say sharks should not unhealthy. You want to incorporate them in somewhat little bit of the science, clarify it. For initiatives like this, we go up there and spend time on the pubs speaking to the fishermen. We’ve even received some fishermen serving to us take samples.”

Bull Shark Bandits is now streaming on Disney+ and Hulu, premiering on NatGeo WILD on July 25, 2023.