h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Many of you may have read about the death of a teenage surfer, killed by sharks, in Australia yesterday. Local police, apparently under the instruction of the state premier, Ken Foley, are hunting the shark.

This sounds very stupid to me. I don't see how killing one shark will do much to prevent further deaths, or raise awareness about how to limit the risk of attacks. Instead, I think the killing (if it happens) will only continue to propagate the 'Jaws' myth of all sharks being man-eaters, the only solution to which is extermination.

Great White sharks are a protected species, too

Story: http://news.bbc.co.uk/1/hi/world/asia-pacific/4103835.stm

Thoughts?

I think they are out to get the shark because if they do nothing at all, the locals will be angry and upset that nothing is being done, however pointless the doing may be.

Do sharks tend to hang around the places where they've last had a good meal? Is it possible that they are worried shark will polish off the entire beach? I'd've thought the best thing to do would be to forbid swimming in the area until shark has gone off to find a marlin to eat or something. Or would that damage the local economy?

Anyone know much about shark habits?

My personal opinion is that humans should jolly well learn how to deal with the world around them and stop being amazingly foolhardy and then amazingly vindictive when their foolhardiness gets them eaten by after all a perfectly respectable shark/ tiger/ enraged badger whose duty is, after all, to eat stray mammals wandering into their territory. It's what they do. It's what they are. It's like punishing a tree for dropping conkers... no, wait, we do that too, don't we?

Sharks, unlike tigers and other species, do not "acquire a taste for humans". They eat whatever they eat because that is what they do.

Obviously, the State Premier isn't aware that death penalty doesn't work as a deterrent with humans, and it isn't going to work on sharks.....

Normally, great whites don't bother humans because humans don't turn up where great whites usually eat. They normally swim well offshore, far away from surfers and swimmers, and eat seals, dolphins and other stuff like that. Only when the shark goes somewhere unusual, i.e. close to shore, does it become a problem.

When this does happen, there are a number of options, including simply not allowing anyone to go in the water in the hope the shark will get hungry and go somewhere else. Sharks don't just eat people, however, and there's no guarantee that will work. Nobody has ever managed to capture a great white alive, so transplanting them somewhere harmless isn't realistic, and simply shutting down the beach - which in a lot of coastal areas is the driver of the economy - is not realistic either.

Which leaves killing the shark. There's no suggestion here of deterrence. Basically, if you've got a great white stalking your beach, it will continue to do so until you kill it. When you kill it, the problem is gone. We're talking about ONE shark, and most likely one that is not in the normal breeding pool of these rather strange creatures anyway.

Bear in mind - hanging around beaches eating humans is deeply odd behaviour for a great white, or indeed any shark. The ones who do it are NOT the normal ones, they're the strange ones. Who knows - the gene pool is probably better off without them.

I like sharks. They are incredibly interesting creatures. I am dead against hunting them for sport, for food or for "revenge". But if lives can be saved by killing a single shark, I'm all for it, because in the end human life IS more important.

H.

There were two sharks invovled in the Adelaide, both over 5 meters, and this is the second attack this week.In Cairns (far north east coast), earlier this week a bronze whaler shark took a spear fisherman.

I general I am against hunting sharks, but I do agree with Hoo here, sharks are opportunistic eaters, and if they find humans easier then seals, then they most likely will continue to attack humans

>> "Basically, if you've got a great white stalking your beach, it will continue to do so until you kill it."

If that's the case, then presumably all previous attacks have led to a chain of subsequent attacks, only stopping when the particular shark (somehow identified) was killed, in which case, there would seem to be a huge historical precedent in favour of killing the shark.

>>"Bear in mind - hanging around beaches eating humans is deeply odd behaviour for a great white, or indeed any shark."

Indeed. In fact, eating a human even after they have been attacked seems not to the norm, with ~75% of attack vitcims surviving, (and presumably some of those actually dying still not being eaten).


>>"The ones who do it are NOT the normal ones, they're the strange ones."

I had understood that sharks may well tend to attack humans some of the time because they look (in silhouette from below) rather like the shark's common prey of marine mammals, especially when paddling surfboards. If an attack is undertaken in the mistaken assumption that a human is a porpoise or suchlike, then it is possible that the shark will learn to be more discriminating, will learn nothing, or wil develop a taste for human flesh.
I don't know which of these is likely to be the case. A longtime researchers on Great White behaviour
http://www.abc.net.au/southwestwa/stories/s1149712.htm
reckoned that:-
"there's really no evidence to suggest that any shark having bitten a person, is any more likely or less likely to do so again."
and that (in regard to another attack)
"The chances of finding the sharks responsible or even identifying the sharks responsible, diminishes quite incredibly [over time]."

There may have been several attacks around Australia recently, but it is a large country, and if there's no evidence that an individual shark is more likely to attack a human having already done, so, killing a previous killer is no more likely to reduce future attacks than killing a shark at random.

How many surf boards have you bitten into recently?

There is another angle.

*If* it is the case that attacks are essentially random, and that sharks are not in fact comparable to the kinds of land predators that become habitual 'man-eaters', then effectively people should be consistently careful whether or not there have been any recent local attacks, and whether or not those attacks have been avenged by somehow identifying and killing the shark responsible.

If people assume that the killing of a shark (quite possibly the wrong one) has actually made the sea significantly safer, they may end up being less cautious than they otherwise would be, and it is possible that the result could be more victims, (and more dead sharks), rather than fewer.

Good point. Part of spending time in any kind of wilderness is that it is inherently risky relative to one's levels of knowledge and skill, and luck.

I think that most surfers would have a good understanding of the risk of shark attacks, but maybe surfing is like other wilderness recreational activities where more people who don't know what they are doing are getting involved and often getting into trouble. The idea that killing one shark is going to make the sea safe is actually counterproductive.


If the Premier and other authorities want to kill this shark in order to save human lives why haven't they closed the Adelaide beaches until the shark is caught?

Of course, it's possible that the authorities actually think that it's highly unlikely the shark in question will attack again, unlikely it is still in the area and highly unlikely that they can identify it even if it is.
They may take the view that killing a shark (even the wrong one) will make people *feel* safer, and even if that possibly makes things a little more dangerous with regard to a false sense of security, few enough people get killed in any case that that would remain speculative at best, and they either want people to feel the authorities are doing something useful, or just they don't want to harm the tourist industry.

It was rather disturbing, reading about this shark attack on what was, until a few years ago, my local beach. It's a placid beach - sand, clear water, the odd bit of seaweed, small fish... No sharks. No surf. There can't be surf in a sheltered body of water.

Kea, there's no easy way to close a 70km stretch of beach that forms the western edge of a city of more than a million people. It is much simpler to hunt the sharks.

Sharks are not at all common in Gulf St Vincent, which is the body of water on which Adelaide lies. They prefer deeper water - open water, in fact. It's hard to see what these sharks are doing in the Gulf in the first place. Lost, presumably. If they're hunting together, that's an especially rare thing for Great Whites to do...

I'm not in favour of hunting per se, but in this case I do support the hunting of the sharks. Of course, if there was a way to corner them, sedate them and relocate them to nice deep water, maybe offer them some counselling too, that would be preferable - but it would also be rather absurd. In this case, we have a couple of savage animals who are *not* in their usual habitat, and who are posing a danger to the public. That's the bottom line.

There will not be an open-slather shark massacre - there will be the removal of sharks that are hazards to the public. Kevin Foley - the Acting Premier, not the Premier - has made the right decision.

(I might also add the the BBC has taken a regrettably tabloid approach to this story. It did the same thing with stories of savage kangaroos terrorising the suburbs of Canberra during winter. What a lot of rubbish, the roos ate bits of my garden, but they were very peaceable while they were doing so.)

Ivan.

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az

Sharks DO NOT acquire a taste for human flesh. In fact, to the contrary it is not just that, as Hoo rightly points out, sharks and people do not tend to share the same environment, but that humans are simply not right for a shark diet, especially not the Great White.

Great Whites typically live on seals and other marine mammals. They tend to keep to hunting grounds that contain those types of animals and others that have a high fat content. They are not, unlike some sharks, opportunistic creatures but tend to have a fairly fixed diet - the Meditteranean Great White population, for example, has been endangered due to the fall in the population of the Tuna which they habitually eat. They have not made a shift into alternative food stuffs but have instead steadily dwindled. Some sharks are opportunists, but Great Whites aren't - simply put they require too much fuel to keep alive to move away from established food sources.

Most marine scientists specialising in shark behaviour believe that most attacks on humans by Great Whites are probably prompted by mistaken identity - a surfboard viewed from below is pretty much seal/tuna shaped, or maybe even curiosity. It's unfortunate that a fish weighing as much as a sixteen foot Great White doesn't make for a playful questioning.

The tragedy of this is that is there is no right answer. To risk leaving a predator the size of the larger of the sharks involved in this incident is not only negligent, it has no guarantee of working. Regrettably, losing specimens of this size from the gene pool - at sixteen foot, one of them is above the average size, but nowhere near the record (which is closer to 21 foot, if memory serves) and it would be sad to see the Graet White go the way of the Whale, most species of which have shrunk considerably since encountered by man due to the habit of whalers taking larger specimens.

It is also worth bearing in mind that of many hundred species of sharks, only a very few - certainly less than a dozen are actually on record as 'man-eaters'. The only one which is actually considered 'dangerous' under any circumstances is the *incredibly* bad-tempered and aggressive Bull River Shark.

Oh, and as an aside, Ivan, scientists in New Zealand have been observing not just pairs of juvenile Great Whites hunting, but entire *packs* of up to a dozen or so. There is still a huge amount we don't know about the last great predator on the planet that we cannot tame.

Thanks for that information, Blues. I wasn't aware of that particular research. On this subject I'm happy to take the word of a shark, of course.

Ivan.

The greatest evidence that we are certainly not on the shark menu is the fact that most of these victims live. If a great white were interested in eating a person, that person would be eaten. A human being is out of his element and completely helpless in the water, and is probably the easiest prey the shark will ever see.

What we see instead are single bites. The shark bites down, tastes that it bit into something it wasn't expecting, spits it out and swims away. As long as that one bite wasn't enough to destroy organs or bleed too quickly, the victim has an excellent chance of recovery.

We would know they've acquired a taste for human when all we find are a skull and some fingers.

Blues: It was my impression that tiger sharks were also particularly nasty, being extremely aggressive pack hunters.

Not so familiar with tigers. They are more restricted territorially than Great Whites, and they certainly can be a 'handful'.

I'll have a shufti round the 'library' over the Xmas holidays and get back to you.

I live in the place where this shark attack happened, and many others, the father of this teenager actually said on the news he didnt want the shark killed but rather just start to have more sharks shot..........(cough).........with trackers so that there can be warning of attacks. killing it is pretty pointless, espially since it has gone into deeper waters, and its not staying near the shore.

Well, thats a viable option I suppose. I certainly can't think of a better solution.

Though of course it might prove expensive.

Wow, this has turned into a very interesting debate. I'm really impressed by the forum and its forumites

I'm still not convinced that killing the shark is an action that can be justified. Potholer's statistic of c.75% of people surviving an attack would suggest that feeding is not the primary aim of attacks. I've read that the mouth is the shark's only tactile organ, meaning that bites may be investigatory rather than intended to kill. Furthermore, the large amount of bone in humans means that swimmers and surfers would not appear to be a food resource that sharks could depend on: sharks won't become reliant upon human meat, or be conditioned to like it.

The most obvious solution is simply not to swim or surf where sharks are known to be present and active. Closing beaches wouldn't really be practical, but the provision of information - allowing people to make an informed choice about going in the sea - would be possible. But then, in the middle of summer I'd imagine that this would have quite a considerable economic impact. I doubt that the acting state premier, or many of the tax payers, are prepared to lose so much revenue for one shark.

If anyone knows whether they've actually manage to kill the shark, let me know