How do they find the shark responsible for an attack?

[seekinglondonlife]

Just read the sad story about the British man killed in a shark attack in Australia.
According to the BBC News, lifeguards have been jetskiing and aircraft travelling 25 km to find the shark, which will then be culled. How on earth do they find the responsible one? According to the site, they usually do within a few days. And why do they kill it? Would it be more likely to kill again?

@Iwanttenofthose

In terms of the reason for culling it's not a "taste for blood" as such. Sharks are very visual hunters and when they've had a successful kill they'll form a search image of the thing they ate and be much more likely to attack something that looks like it again, because it was a successful use of their energy. It's an evolutionary adaptation, they hunt from down where it's dark looking up at the surface so they're looking for silhouettes. If they didn't have this ability they'd attack every bit of floating debris and soon run out of energy to hunt.

It's the reason bodyboarders are often targets, they look like seals or turtles etc from below so they match the shark's known search image and it targets them.

So yes, because this person was sadly eaten as opposed to just receiving a tentative exploratory bite wound, this specific shark is very likely to attack swimmers again in future.

Thanks for that. Interesting to read!

Watch Jaws!

Poor guy. What an awful way to die, and the poor guy that witnessed it!
There's just no way I would get in the water in Australia. I live in Scotland and wouldn't go in the water here. I remember going to Spain when I was 15 and being absolutely terrified in the water. I spent the whole time looking down to see underneath me. It's not like it's a complete shock that there are sharks I the water in Australia.

@Iwanttenofthose

In terms of the reason for culling it's not a "taste for blood" as such. Sharks are very visual hunters and when they've had a successful kill they'll form a search image of the thing they ate and be much more likely to attack something that looks like it again, because it was a successful use of their energy. It's an evolutionary adaptation, they hunt from down where it's dark looking up at the surface so they're looking for silhouettes. If they didn't have this ability they'd attack every bit of floating debris and soon run out of energy to hunt.

It's the reason bodyboarders are often targets, they look like seals or turtles etc from below so they match the shark's known search image and it targets them.

So yes, because this person was sadly eaten as opposed to just receiving a tentative exploratory bite wound, this specific shark is very likely to attack swimmers again in future.

Being a pedant, we don't actually know he was eaten. He was certainly very bitten, but unless the shark is opened up, no one can tell if he was eaten. Parts of the body can be lost to sea or eaten by other ocean creatures.

And this is typical for shark attacks on humans, that we aren't actually that good to eat as we aren't as fatty as ocean mammals, and we have more bone relatively. So it could be argued that a shark that has bitten but not eaten a human is therefore less likely to attack a human again.

This is sort of moot as the swimmer was wearing a dark wetsuit. The shark probably thought it was biting a sort of seal.

@JustMsInvisible

Watch Jaws!

I have. Many times.

The author ended up regretting the book as it contained SO many inaccuracies and created so much fear, with the films then doing this to the power of 100.

I believe they have sonar equipment

They can't, it's ridiculous & nor should they.
I have every sympathy that a man has lost his life & for his loved ones loss but the shark was just fulfilling it's natural instinct to feed itself in it's habitat.

True but with diminishing food supplies, rapidly changing habitats and increasing debris in the ocean it's very likely that the shark would have eaten what was available even if it wasn't as nutritional as a seal would have been, and also would go for the same thing again in future in the absence of better quality food.

You're right though, if the area had an abundant supply of decent shark food they'd be unlikely to choose a human over something like seal.

Unlikely to be many large shark species in the immediate area. I suspect they’ll kill any large great whites they locate in this search given the risk to human life if they don’t.

DS lives in Bondi and often swims/surfs in these waters.

He text first thing yesterday to say 'I'm alive'. It's affected everyone in the area, and the water was empty even before it was officially closed.

Apparently sharks see people in black wetsuits as seals, which is why they attack, but it was interesting to read what @Iwanttenofthose wrote, that essentially having had a good experience at eating a human, it may well return. I kept telling DS to get a yellow wetsuit - he might listen to me now!

So sad for the guy and his family.

And for all of the people living in that part of Sydney who are 'living the life', and have suddenly had to rethink. The only possible benefit is that DS might now find the boring old UK more appealing!

As with everything, it'll all boil down to money.

If they don't kill it, then people will avoid entering the water in that vicinity, thereby compromising tourism and other businesses.
As others before have said, we are an arrogant, stupid species.

They’ve said they’re not looking to kill it. It’s standard practice to tag great whites and monitor their movements, that way they can enforce the shark alert system if one swims very close to the shore.

Sharks are very visual hunters and when they've had a successful kill they'll form a search image of the thing they ate and be much more likely to attack something that looks like it again, because it was a successful use of their energy.

It's the reason bodyboarders are often targets, they look like seals or turtles etc from below so they match the shark's known search image and it targets them.

But don't those two sentences directly contradict each other?

If a person is attacked because their silhouette looked like a seal and stimulated the attack behaviour instinct, then there's nothing to add to the database? It was acting based on the existing database of a seal silhouette, nothing different to add.

I could understand your point if we were saying the human looked different and was attacked to find out what it was, and then upon learning it's an animal the silhouette added to the database. But we're not, are we?

I thought the current understanding is that the attack style of charging directly upwards from deep water like was observed here, was a case of an environmental stimulus triggering that particular behaviour? Like running a way from a bear would trigger an attack. Not like the shark is being tactical and planning.

that essentially having had a good experience at eating a human, it may well return

In the nicest way possible, if it had had a "good experience" with eating the human would there really have been any body parts left to be retrieved from the sea? (As reported by BBC).

Not sure @formalineadeline but I did read that it came back to get more. I suppose that the tide could/would have dispersed some, as the shark could not get everything in one go?

It's sad for both sides , I completely get the argument that the shark was in its own territory and doing what is natural for them-hunt but I also know if a shark attacked my child whether they were young or adults I would want to kill it probably personally if I could, as crazy and not rational as that sounds I think it human nature to want revenge or justice and maybe despite knowing that actually a shark doesn't understand the hurt it's caused that for the people and family close to the event it's a type of closure , I don't know maybe the best thing it's to just not enter the water where there are predators but I suppose in the moment with the sun shining the sea looks inviting and the chance of it happening it extremely rare.

Also as shark attacks are so uncommon the amount of sharks killed for this reason will be very small as well? There are far more sharks killed simply so we can have a tin of tuna for example .

I remember doing a project on sharks when I was in primary school and the books all said that sharks spit humans out as they aren't their taste, but usually bite them mistaking them for a seal.

@formalineadeline Well no, it's not contradictory at all, because it might not be the food they were looking for but it's still edible so it'll be added to the database as something edible. It's like it aimed for a big mac and got a chicken wing instead. It would still have got some nutrition so as I said before in times of scarce food supply, there's no reason to think it wouldn't target swimmers again.

If a shark genuinely thought what it had bitten wasn't food, then the swimmer likely would have suffered one bite, not a sustained attack, and may have had a chance of survival.

And sorry to be graphic and this isn't meant to be flippant at all, but bodies float, so if there were only "parts" remaining on the surface then I'd say it's a pretty safe bet that something ate the rest.

I’ve been pondering this today.

Horrible tragedy. But the shark shouldn’t be destroyed.

I remember doing a project on sharks when I was in primary school and the books all said that sharks spit humans out as they aren't their taste, but usually bite them mistaking them for a seal.

Thats usually when they bite surfers as they get a mouth full of surfboard. A shark doesn't want to eat a surfboard but I cant imagine it being that picky over what kind of 'meat' it eats.

But you said it was based on the visual image? Not taste? I thought your starting point was to rebut the idea that it would attack again based on taste?

And if attacking based on visual image that looked like a known image, what difference would there be to learn?

I thought that's why the safety guidance is about not going in the water at dawn/dusk etc etc because the light conditions are too poor to tell the difference between a human on a surfboard and a seal?

So there won't be any distinction for it to make.

I'm not being argumentative here simply curious.

I'm so tired of people banging on about the poor shark, nothing is going to happen to it. They are not looking for the shark to kill it.

They will chase it back out to deeper waters, they also need to make sure it's not still in the area before beaches can reopen.