The Secret Life of Sharks

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BBC Sounds, Music, Radio, Podcasts.

Hello, I'm Brian Cox.

I'm Robin Robin Ince, and this is, well, the show that used to be The Infinite Monkey Cage.

Yeah, because tonight we've been told to widen our audience, you know, to be a bit more discovery channel, while still maintaining, though, Radio 4 sensibilities.

So today's show is when sharks don't attack nearly as often as many presume due to the way that they portrayed in popular culture.

And in fact, more often than not, what sharks do is just sometimes eat much smaller things than than surfers.

Indeed, many things that are non-mammalian.

So there we are.

We've got some very exciting interviews.

We've got three surfers who one day, it was actually Christmas Day, went out surfing on Bondi Beach.

And two and a half hours later,

they came back.

Everything was fine.

They had a really nice time, actually.

One of them said it's the best Christmas they'd had.

Yes, today we're exploring the secret life of sharks.

What is the secret of their evolutionary longevity?

What makes them such great hunters?

And is there a gap between their fearsome reputation and reality?

Today we are joined by a physiological ecologist, a researcher in biological and environmental sciences, and a Boa constrictor, botherer and ballroom dancer.

And

they are.

Hello, I am Lucy Hawkes.

I'm a senior lecturer at the University of Exeter and I use electronic tracking devices to find out more about sharks.

And my most wonderful experience with sharks was in the Red Sea.

I got in the water surrounded by fish, guts, and blood.

I was hanging in mid-blue water, about 10 meters underwater, with sharks circling me with an electronic tracking device on the end of a spear, willing the sharks to come close enough to me so that I could tag them.

And I thought my mum would kill me if she knew what I was about to do right now.

Hello, I'm Isla Hodgson.

I have a doctorate in zoology and I'm a professional shark nerd for the Save Our Seas Foundation and I worked with Baskin Sharks for five years up in the Hebrides.

And my most wonderful shark experience is being in the middle of a real life sharknado, so a shock tornado, with Baskin Sharks, which means it was a very slow tornado, but still a shocknado, nonetheless.

My name is Steve Baxhall.

I'm a naturalist and my favourite shark encounter was with a single male blue shark who stayed with us for about an hour and a half, ignored all the food in the water in favour of tactile interaction with us in the water.

There was never any sense of threat, but over the course of the interaction, I discovered that sharks can have personalities and characters as complex as any seal or dolphin.

And this is our panel.

Lucy, when do we we first see sharks in the fossil record?

Sharks are among some of the first vertebrates that evolved, and about 400 million years ago, sharks started to come out of the oceans.

And there are some very old families of sharks that are still extant today.

So, six-skilled sharks in particular have a very, very old evolutionary lineage, whereas something like hammerheads are comparatively very young, only about 20 million years old.

It's a remarkable thing, I mean, 400 million years ago.

So, that's some of the first,

well, very large living things, I suppose, when we see the first things emerging, what, 550 million years ago or so?

And still essentially the same in many ways, some of them.

Their body plan has been so successful that it's persisted all of that time.

Sharks have also survived through essentially five mass extinction events that have wiped out huge other numbers of species.

And of course, all of the sharks that have ever evolved are not around today.

Many also became extinct as well.

But sharks have just been so successful, they've just stuck around all of that time.

Isla, what is that secret of basically being such an evolutionary success?

So, when we think of the word shark, we all think of jaws or the great white shark.

But sharks are actually a hugely diverse group of animals, which means they inhabit lots and lots of different niches, and in particular, the deep sea.

So, there are sharks that exist in the deep sea even now.

The sharks actually survived a mass extinction called the Great Dying, which sounds really depressing, and killed 96% of all life on Earth, which is astounding.

But because the sharks were in the deep sea, they kind of seem to avoid that.

We tend to think sharks are ancient, and you might think, well, they were around when the dinosaurs were on the land, but that predates the dinosaurs.

They're older than the dinosaurs, which is my favorite fact about sharks.

Well, they're not only older than the dinosaurs, they're older than trees.

Older than trees, yes.

Really?

Yeah.

Back then, there was no complex life on land, really.

And all of a sudden, this flourishing marine environment underwater, this incredible predator arrived.

And they weren't all very big to begin with, but after a while, some of the real giants started to emerge and absolutely dominated the seas.

So now we have a far greater excess of bony fish around than we do cartilaginous fish, but there would have been times in prehistory when there might have been 80% of the animals underwater would have been effectively sharks.

Well, you mentioned that, the cartilage.

So is that the main difference between sharks and the other fish lineages?

That's right, and I think it's one of their, you know, as I was kind of suggesting, there is no one single reason why sharks have been so successful, but that cartilage skeleton is certainly one reason for it.

You know, it's more flexible, more malleable than bone, and it's enabled them to develop this incredible diversity of forms from the tiny little dwarf lantern sharks that are the length of a ruler, right up to the mighty whale shark and even megalodon and other prehistoric species that might have been even bigger.

And it gives them such an advantage.

Why did fish bother evolving bone then?

Certainly, for those who are believing in the creationist theory, I have certainly enjoyed your phrasing of why did fish bother?

I'm sorry, lads.

I'm gonna make

my career just ended.

I understand it.

Brian revealed he was a flat earther

looking wonderful.

I do say it with a smile on my face.

I understand that.

What don't you say with a smile on your face?

It's how you've made your career.

Even when we talked about the death of the universe, I've never seen a man who's looked more happy go lucky.

Steve is met.

You were trying not to smile, weren't you?

And you went, it doesn't work anymore.

Sad muscles are broken.

Actually, I think we can start to train those sad muscles up because, having just talked about how fantastically successful sharks have been, there's really bad news about what's happening to sharks now.

And if I could get the listening public to feel one thing from this, it's that we should give sharks a lot more love because sharks are brilliant, sharks are important, and sharks are the second most threatened group of vertebrates on the planet after amphibians.

Things like oceanic species of sharks have probably declined by something like 71%.

Sharks are really in a really, really bad way.

There are more species of shark that are threatened with extinction than there are mammals.

So, do you feel that?

I mean, I know that Peter Benchley kind of regrets writing Jaws, and he, I believe, has spent a lot of the money that he made from that investing in trying to make people realize that this image of the shark as a violent predator was something that's not really true.

Do you feel that message is getting through, or do you feel that there's still an idea that sharks are very, very dangerous, that they're huge risk?

Where do you think we've gone in terms of that?

I reckon I could walk outside this studio and ask a hundred people if they think that sharks are violent predators, and most of them would say that they are.

I think we still have this very negative view of sharks.

And don't get me wrong, sharks are awesome predators, but they're also gentle plankton eaters and they're also graceful bottom carnivorous rays as well.

You know, sharks occupy these huge range of different niches.

And I mean one of the reasons that sharks are cool is because a great white shark can leap itself out of the water, smashing a great big fat seal for a massive dinner.

You know, they are fantastic animals and they are very, very capable predators, but they really pose us no risk whatsoever.

And on this panel today, of course, are quite a few of us who've been in the water with sharks and would happily get back in the water with sharks.

There are very few sharks I wouldn't love to get in the water with.

And on on the other hand, there are some species that I wouldn't particularly want to get in the water with, like an orca.

Yeah, I'm a little bit dicey about cetaceans.

Not my fave.

Sharks, though.

If a shark turns up, I'm getting in the water.

Yeah, never trust an orca.

Right.

Now, I don't know if I told you this, but an orca once ate my homework.

I was in the middle of.

True story.

I was in the middle of tracking an Atlantic bluefin tuna, which had had a lovely life in Falmouth Bay when I first found it, swam itself down into the Bay of Biscay in France, went went to the Mediterranean to breed, was wearing a $5,000 tracking tag I'd put on it, and an orca ate it.

Completely ruined the project.

The orca as well, when we talk about sharks, a great white is probably the most famous apex predator that we have, also seen as one of the most dangerous species of shark.

In South Africa, there's a place called False Bay, which is a.

If you think about shark-infested waters, I hate to use the phrase, but that's what springs to mind.

There's one of the biggest pop or was one of the biggest populations of white sharks in the world in False Bay, really famous area to go cage diving or go diving with the great whites, world famous.

And in the space of five years, all the great whites have pretty much vanished from the area.

And the reason for that is to orca.

And it's quite a cool little forensic crime story.

So there's also a species of shark called the broad-nosed six-scale shark, also a predatory shark, hangs around kelp forests in South Africa.

And there's a couple of really famous dive sites that that you can go diving with them, and pretty much every time you were guaranteed to see them.

And one day in November, divers went down to the site expecting to see Six Gills all happy and you know doing their thing, and they actually found almost like a graveyard.

So, all of these sharks lying on their back, each one of them with the exact same injury.

So, almost with surgical precision, their liver had been removed, nothing else.

The sharks had just been left.

And so, these divers were like, What on earth has happened here?

Everybody was hugely confused, thought it was fishermen.

It happened again, a second time.

And then white sharks, these great big predators that we've been taught to fear, rolled up on the beach with the exact same surgically precise wound on their body.

And it's only through drone footage and helicopter footage that scientists discovered that it was actually two orca.

So the liver of a shark is really fat-rich.

They've got a special oil in the liver called squalene.

And the orca had learned that this is a pretty good way to get a meal.

Two orca managed to chase away one of our largest apex predators from the area where they used to be.

So basically, we both hate orca, essentially.

That's an incredible story because one of the things very often when we talk about kind of environmental issues that are caused by human beings and waste, it's that idea, isn't it?

Which is we sometimes destroy things for a tiny part of them and then the rest is thrown away.

And here we seem to be seeing a level of intelligence that means that an orca is almost as stupid as we are, if you see what I mean.

They are fabulously wasteful creatures.

They have also, and this has been filmed for the first time relatively recently, learned to take advantage of a kind of chink in the armor of the shark, which is that some shark species, under certain conditions, particularly if they're flipped over onto their back, will go into a catatonic state called tonic immobility.

It's something that biologists can use as a way of getting a shark to be passive so they can study its stomach contents and they can take various measurements from it without it going through any stress or any anesthesia.

And in some cases, it's as simple as turning the fins of a shark or flipping it over onto their back.

And the orca have learnt that they can do that.

And it's been filmed happening with fully grown great whites, just flipping them over onto their backs.

And then the shark just lies there like, and I mean, it can be actually quite a restful thing.

I've had sharks that have gone into tonic immobility and they're just lying on their backs like, oh, that's just fantastic.

Oh, that's just great.

Sometimes if you just like stroke their noses, you can see their eyes rolling back and they're like, oh, that's the best thing ever.

Like a dog sort of like being stroked stroked on a fireside rug.

And the orca have learnt to use this little chink in their armour to their advantage.

See, never trust an orca.

But you mentioned what is it about the liver?

So this is something that humans have been doing, obviously, on a regular basis.

What are the other reasons in terms of human action that sharks are seen as something

worth killing?

Well, so many different reasons.

Most sharks are probably being killed today by accident as bycatching fishing nets that are just not good at discriminating between sharks and target species they really want to catch.

But we eat shark, we even eat shark here in the UK.

If anyone's been to the fishmonger or the fish and chip shop and had flake or rock salmon, that's shark.

It can be delicious.

There are some species of shark that are thought to have very, very tender meat and that can actually sell for a really high price.

We all probably have heard of the global trade in shark fins, and shark fins still are considered a very prestigious type of food to consume, but they've become more and more accessible to more and more people as people people have started to move into higher income categories.

And so, sharks are being finned in massive numbers.

You said that they fill many ecological niches.

So, how many species of shark are there?

I was just chatting to there's a guy called Dave Ebert who he has lost shark guy, which is a very, very cool title.

And his job is to keep track of this.

And so, a couple of weeks ago, it was 536.

I don't know how much by, but that number has already gone up because they've discovered new species even within the space of a couple of weeks, which is just mad.

Can you give us a sense of the range of them?

What's the smallest known shark and the largest known shark?

The weirdest shark.

Oh, this is like you just want to go out for a while.

I need to go out far for now, but could you just say big shark, little shark, and weird shark, and I'll be back.

I'll be back at about 8:30.

I just want a picture of the diversity of these animals.

So we know what the biggest shark is.

The largest shark in the world is the whale shark, which can be over 50 feet long, so the size of a double-decker bus.

Amazing animals, but they are filter feeders, so they feed on plankton and tiny krill and things like that, so completely harmless.

And then the smallest species of shark, there is a little bit of a debate going on.

So there's the pygmy lantern shark, which is eight inches, so can fit in the palm of your hand.

Pygmy lantern shark.

Uh-huh.

And then my personal favourite species of shark, I'm so glad that you brought this up.

There's two sharks called pocket sharks.

So they were brought up in deep-sea trolls across water that's about 3,000 meters deep.

So we think at least these sharks exist at about 500 meters.

And there's only one specimen that came up and it's so rare that usually scientists, when they get a new species, we love to dissect it for some reason.

But we didn't do that.

We sent it to get an x-ray.

And this species, they're called the pocket shark.

So this specimen was about 14 inches in size, so tiny, tiny little thing.

But the coolest fact about the pocket shark is the reason it's called the pocket shark is because it has glow-in-the-dark armpits.

So there's a little slit behind the pectoral fin, which is filled with bioluminescent fluid that it can fire out at will.

It's firing out at will.

In which particular scenario will it fire out at will?

Well, we're not certain, we don't know for certain, but most likely in a threat scenario or so to either distract a predator or some other deep-sea species like the fire-breathing shrimp, which is another very cool species, which vomits up bioluminescent fluid.

Can I just check, by the way, how many of these are you making up?

Just on the hoof?

All of them, all of them.

But that's a beautiful idea that it kind of creates its own firework so that the predator goes, ooh, oh, it's gone.

It's a beautiful image.

It's amazing.

It's so cool.

And this little thing.

Steve, you've dived with a huge number of species, haven't you?

Was it?

I read 100 different species or something like that.

Could you give us a sense of those experiences you've had with the different sharks, the big sharks, the little sharks, whale sharks?

Brian wants to go out again, so if you could tell every single one of the hundred ones, an anecdote on each.

It varies so tremendously because they all fulfill such different niches in very, very different environments.

You know, wandering around in the mangroves in the Bahamas with tiny lemon shark pups kind of nuzzling around your knees is a very very different experience to swimming in blue water alongside a great white shark.

You know, the two things could not be more different.

So you've swum with a great white, not a cage, just swim because very few people...

You said there were few sharks you wouldn't swim with.

Yes.

Is a great white on the list of things?

I would definitely get in the water with a great white.

And I went cage snorkeling with blue sharks off the North Cornish coast once, and the sharks were fascinated by the cage because you kind of get this, you know, slight current flowing between the metal bars.

But I was so frustrated that I couldn't get out of the cage because I wanted to be with the sharks looking at the cage.

I just wanted to get out, and I'm quite confident that it wasn't a dangerous thing to do.

They were fascinated in what was going on, really.

It needs to be done at the right time, in the right situation, with the right water quality and the right animals.

And believe it or not, you can actually assess the body language of individual sharks.

So, if you spend a little while watching them, if you see a shark that drops its petrel fins, then it's getting ready to make a tight turn.

If it arches its back and opens its mouth and its gills are billowing, those could be leading towards signs of a territorial aggression, particularly then if it starts twitching its body in aggressive movements.

But if they're just cruising with their petrel fins spread wide like wings, then they will completely ignore you.

And in blue water where you can see the sharks and they can see you and they know that you're not their chosen prey, they will swim straight past you to get to food that's behind you.

I suppose it's a cliche, isn't it?

Or some accepted wisdom that these things are just killing machines.

Whereas whales and dolphins and things we think of as having a very high intelligence.

So what do we know about shark intelligence?

First of all, the areas of their brain that are dedicated to their senses are extremely well developed, particularly those connected to their sense of smell.

There is direct evidence of sharks having friends, particularly young shark pups, will hang out with the same individuals for an extended period of time and interacting with them in ways that appear to be social.

There are different species that will interact together to have better success in hunting.

There is surely a lot still to learn about them, but this is definitely not just a mindless hunter that swims with its mouth open at anything it can eat.

Lucy, what do you, I mean, in terms of, I mean, having watched Steve on Deadly 60 and the shark shows, you know, sometimes when he's sitting opposite a Taipan snake, and you think you've really got to have worked out exactly what the behaviour pattern is.

And so for when you're diving with sharks, I mean, the research beforehand, I mean, is it trial and error?

Do you go to a graveyard and just see all of the different marine biologists the different ways that they've died in the past and go, well, won't do the same as Jean then.

He obviously, you know, how do you make yourself feel safe in that?

Well, whenever we do work with species of wild animals, we do do an awful lot of background research.

We would typically talk to local fishermen, work with local fishermen who have, you know, amazing knowledge that really complements our own scientific perspective on stuff.

We would talk to a local ecotourism guide, you know, we'd gather all the information that we possibly can to understand what an animal is doing when it's there, when it's going to be there, what the best time of day is to interact with it, for example.

For somebody like me who's just trying to catch these animals in order to put tags on them so that I can understand more about where they go, it's really fundamental for me to talk to people who are out there all the time seeing them, which I can't be because I'm usually at my desk analysing data.

You've brought some of the tags along, haven't you?

Can we?

So, this tag is called a mini-pat.

So, it's maybe seven centimeters long, like a dark grey thing with a sort of like a 10-centimetre antenna on the top of it.

And these are normally attached onto sharks.

They would measure generally three things: they measure light, temperature, and depth, and that can help us to understand what the animal's been up to over the whole course of a year.

And the reason that they can do that is because if you measure light, you can work out things like how long the day is, and of course, the length of a day varies with latitude.

You can also work out relative to a clock what time the sun's coming up, and of course, that's telling you a little bit about longitude.

So, just by measuring light, I can actually work out where an animal is.

So, I had one of these tags on an Atlantic bluefin tuna, so not a shark, sadly, and I was busy collecting data from this fish I'd spotted at going into the Atlantic to breed.

And when these tags finish collecting data, they automatically pop off, and this thing comes up to the surface and transmits the data.

And this thing washed up on a beach in France, and a lovely lady called Bergitte was walking her dog and found it.

It's got an email address on it, so she emailed us and said, I have found this thing on the beach.

Would you like it?

Sorry, I had to do that.

And we said, Yes, please.

So we gave her 150 euros.

She sent me an email.

You're right, she did email us with a French accent, obviously.

To be honest, I'm enjoying this meeting of a low, aloha, and Jaws, too.

Anyway, so we get this tag back, and for the last two weeks before Bigit found this tag, it had gone completely dark.

So the whole time it was really, really dark.

We could see from the depth sensor the tag was going up and down through the water column, so we could tell it was definitely on something that was alive.

But the key thing was it's measuring the water temperature, and the tag was telling me that it was exactly 37 degrees Celsius the entire time, which is the diagnostic body temperature of a mammal.

So it absolutely had to be inside a mammal, and that would explain why it was dark and going up and down through the water column.

So we got it back, rinsed the poo off, and downloaded the data.

So, how do you attach them then?

I've got another problem.

Here we go.

So, this particular tag is possibly the coolest of the lot.

It's basically sort of a five-centimeter by five-centimeter sort of perspex lump with some circuitry in it, and it's attached to a large yellow float.

And this thing is a little bit like your smartwatch, it's kind of counting steps, if you like.

So it's got something in it called an accelerometer, which imaginatively records acceleration.

I put this very tag on a basking shark in Scotland, and we were just trying to find out what they got up to.

But what they got up to while wearing this tag was breaching.

So we're all kind of probably familiar with humpback whales breaching, leaping clear out of the water.

Well, 10-metre-long Scottish basking sharks do it too.

And they did it while they were wearing this tag.

And unbelievably, we're able to find that these sharks are swimming down to about 20 meters, then they aim at the surface and swim like hell, launch themselves out at the surface, go back down, and they'll do it again and again and again.

And one of our sharks breached four times in just 47 seconds.

Thank you for the ooh in the audience, I'm straight

because it's amazing, and it's so hard.

My wonderful PhD student, Jess, has been attempting to breach herself.

She headed to the local swimming pool and tried it, it, and she couldn't do it.

It's really hard.

It's hard.

It's hard.

I've tried as well.

It's really hard.

As you said, Steve, actually, we don't know.

We know a lot about sharks, but there's a lot that we don't know.

Maybe Eileen, give us a sense of the life cycle of...

What do we know about how they live, how long they live?

Well, it's actually interesting to talk about the diversity, just even within that.

So we could spend a whole day talking about all the different sharks, all the different life cycles.

Lock the doors.

You're not leaving.

So we have sharks that live for, you know, maybe up to five to ten years.

Or we have sharks like the Greenland shark, for example, which can live up to, we think, 500 years.

They're from a family of sharks called the sleeper sharks for obvious reasons.

They tend to live life in the slow lane.

So their preferred swimming speed is about 0.7 miles per hour.

So if you want to prolong your life, there you go.

From the Greenland shark.

Sharks in general are quite slow to reproduce.

The Greenland shark takes the longest, so we think they take about 150 to 250 years to reach sexual maturity.

Yeah.

Yeah, so they are the oldest living vertebrate that we've said the oldest living virgin.

But they probably are badgers.

We haven't talked about, first of all, conception.

Yeah, very true, which has very, very rarely been seen.

The only time that we've managed to film it actually was with white-tipped reef sharks on a seamount in the eastern Pacific.

And it is hands down the most brutal display of mating I've ever seen in the animal kingdom.

And I had to be quite careful about how I try and describe it because, you know, it's really intense.

One single female pursued by perhaps 20 males, she might have a skin that's five times thicker than the males to ward off their advances because they latch on to her gills, thrash her around, smash her down to the bottom until the animal literally looks like it is dead.

And, you know, several lucky fathers have the opportunity to sire her offspring.

And eventually, this poor female shark that's lying on the bottom looking like it's dead will get up and swim away and be, to all intents and purposes, fine.

It's no wonder they wait for 200 years before.

I'm not doing that.

One of the advances that's happened just in the last couple of years that's helping us to understand this whole part of the life history of sharks that we probably are not going to get to see in that kind of forensic detail are things like underwater ultrasounds.

So I did that for the first time about five years ago with stingrays and we had to take the stingray out of the water and anesthetize it and run through this process of ultrasounding it.

But now the technology has developed to such a degree that you can swim alongside a shark and just roll the ultrasound on its body as it's swimming.

And we've done that with manta rays and you get to see what looks like a tiny rolled up burrito inside the manta ray of its youngsters.

We've done it with critically endangered great hammerhead sharks, seeing these a dozen in each ovary, these teeny, tiny, perfect replicas of a hammerhead shark inside this critically endangered animal.

And most excitingly for me, I think, with whale sharks.

And we're talking about these incredible tags Lucy's been using.

The one that I've seen used the greatest effect in the last few years was on a giant pregnant female whale shark.

And this tag followed her for six months.

It showed that for the entirety of that six months, she stayed within the top 200 meters of the sea, apart from one 24-hour period where she dived down to a mile in depth below the surface.

And it seems like a pretty good hypothesis that she's dived down there to give birth to her pups.

But that could well be something that we will never see.

So, the last five years, I've accidentally become,

I can't think of the best way to put this, but a shark pornographer.

Because, so we were talking about

the best you can do.

Yes, I think it is.

We were saying we haven't seen very many sharks giving birth, and basking sharks in particular, we've never seen them mating, we've never seen them giving birth.

And so, we commissioned a special camera and put them on some basking sharks in Scotland, which is a place where we think they probably are gathering, probably to court and possibly to mate.

And then, kind of all just basically went back onto land, crossed our fingers, and really, really hoped that somebody shagged on camera.

Sadly, they didn't, but one morning, morning, about half past five, one of our sharks wearing the camera, as the sun came up, the sort of the gloom began to get brighter and brighter.

And there was about five basking sharks, and they were kind of touching petrel fins and swimming over the top of one another.

And we were just like, Oh my god, so we really thought we'd nearly got it, but sadly, nobody was up to it that day.

The footage is amazing, though, because it looks like they're holding fins into the water, which is the sweetest thing, because it's so exciting as like a shark scientist, because shark sex, as Steve was saying, is famously quite brutal.

So, anything that makes it look like it's a slightly nicer experience is just a joy to behold.

A recent thing that happened last year, a paper was just published about Baskin sharks, which is called The Courtship Taurus, which is where the shark NADO story comes into it.

So, if you're a shark pornographer, I don't know what that makes me, because I was potentially in the middle of, well, the lead-up to the main event.

I think the term is a fluffy

shark fluffy.

Might put that on my Twitter bio.

Put it on your CV, yeah.

It's a really awesome behaviour.

So we don't know much about basketball shark mating.

We've still not seen, unfortunately, the final event.

But there is something called a courtship torus.

Scientists started to notice something a little bit different in their behaviour.

So there were aggregations of sharks who were not feeding, they had their mouths closed, and they were swimming very, very slowly in a circle.

And so I've accidentally found myself in the middle of these, in the Hebrides.

And the sharks are going very slowly around you, but there's also sharks beneath you, so they kind of go in layers all the way down to we think about sixteen meters.

We do think that it's possibly linked to mating, so it's possibly a way to for other sharks to check one another out and go, Hmm, that one'll do.

So we're not entirely sure, but it it is the most amazing thing to witness.

I mean, this one time I went on a hen party in Brighton and it was a bit like that.

We were going very slowly in a single.

Now, our picture of sharks is of maybe solitary animals.

So they come together at times like that, presumably to mate.

Do they ever live in larger groups or do they separate and are they solitary and then come together only when they mate?

Rather marvellously, the collective noun for sharks is a shiver.

And there are many sharks that will gather in shivers that can number hundreds.

You know, being below a shiver of scalloped hammerhead sharks, for example, swirling around a seamount, gathering in these enormous numbers, or silky sharks in the same sort of locations.

Those are probably temporary, or at very least, a sort of vision-fusion kind of thing, where they'll come together for a specific purpose, whether it be gathering for mating or potentially gathering for food.

There are some that will hunt collectively.

Certainly some of the reef sharks will hunt not just collectively as a part of.

of their own species, but with other animals as well.

So yeah, I mean, they can gather in really large groups and sometimes stay together with those groups for a protracted period of time.

Lucy, there was a mention of basking sharks there, I believe, in your prop bag.

I've got something very special to show you that not a lot of people have ever seen.

So, as Isla said, basking sharks do eat plankton, so they don't typically need to have teeth, right?

And I think that even most shark experts probably don't realise that basking sharks have teeth.

Well, one basking shark has less teeth because I've got them here in a jar.

I'm going to pass them around to the gang.

These are extraordinary.

For the second largest shark in the world, so these are sharks that can regularly reach eight to twelve meters.

These teeth are maybe a millimetre long.

If I was to drop them on the floor, it'd be a real job to find them again.

They're teeny, tiny little things.

And these ones were taken out of a dead basking shark that washed up on the beach.

I mean, they were actually cleaned up by a dentist

with the spectacular help of a PhD student.

I don't believe you.

I think you've killed a fairy.

I know.

Amazing.

They're smaller than grains of rice.

If you were to take a grain of rice and chop it into maybe five bits.

What are they for?

What are they for?

They're probably largely for mating, actually, because it probably helps them to get the grip on the pectoral fin of the female to then wall around them.

It could also just be an evolutionary kind of feature that just hasn't died out because it didn't really need to.

These teeth are probably being continuously produced all of the time and shed all of the time as well.

You can find enormous amounts of shark teeth because they discard them constantly throughout their lives.

So a good-sized great white shark could get through 30,000 plus teeth in its lifetime and they're constantly being regenerated and rolling forward almost like they're on a conveyor belt to take the place of the ones at the front of its mouth which are active.

And if you were to, for example, swim underneath the docks where Hemingway used to fish in the Bahamas, where bull sharks have been gathering for years, you can just sip through the sand and gather handfuls of bull shark teeth because they're hard, they're heavy, they fall out constantly.

And it's one of the reasons that we have such an understanding of sharks in the past because they're the one part of their body that readily fossilizes.

And each individual tooth tells you so much about what that shark does.

Regular listeners will have listened to our biological programmes.

We've done quite a few recently.

And each one of them has been gruesome.

And I asked you, Adam, before we came on, I said, there must be a gruesome story for our set about sharks.

And you had one about me.

At no point did you look like, oh, hang on a minute, that might take a while.

It was like a speed of roller deck as you went, that's gruesome, that's gruesome, that's gruesome.

Oh, and then suddenly your face lit up and you went, This is the really gruesome one.

Well, have you ever learnt about something and you're just like, I can't stop thinking about it?

That was this for me.

There is a type of barnacle that eats sharks.

So, you know, that little benign thing that you see on the beach, that little conical shell?

There is a relative of that that is a shark-eating barnacle, and it is wild.

So, it's called Anelasma squalicola.

So, it's evolved an organ.

So usually the organ that the barnacle would use to attach onto rock or attach onto the surface of something.

They've used to burrow into the flesh of deep sea sharks and it is gruesome.

Scientists discovered this on a deep sea species of shark called the velvet belly lantern shark.

And they found a group of these sharks with barnacles buried in their head, buried in the side of their body, just sticking out of their flesh.

And what these barnacles are doing are just sucking them dry of nutrients the whole time.

It's like something out of a horror film.

And a couple of weeks ago, my favorite scientific paper that's probably ever come out was scientists that were studying Greenland sharks, you know, those guys that live for 500 years.

And they found one of these shark-eating barnacles in its anus.

So, not only do you have to live for 500 years, but you also have to put up with something like that in your body.

Worst ever case of piles, isn't it?

Now, something we do need to also talk about.

We've talked a lot about competition in the animal world and competition amongst biologists as well.

So, earlier in the series, we had Serian on, who loves wasps and is so bored of the fact that everyone goes, Aren't bees great?

Now, in the green room, we were having a little bit of a conversation about the fact that dolphins are very much the kind of undersea panda in some people's kind of view.

And yet, it seemed to me that there was a certain attitude towards dolphins from those who love and research and tag sharks.

Lucy?

Yeah, I'm gonna say I'm guilty of that one.

Yeah, I mean, I think a dolphin's you know, a dolphin's all right, you know, it's pretty

people love dolphins, but they're just you know, oh, I love dolphins, yeah, okay, but they're not as cool as sharks, they're nowhere near as old as sharks, they're nowhere near as specialized as sharks, they're nowhere near as awesome as sharks, and they're nowhere near as endangered as sharks either.

And you can see a dolphin anywhere, basically, but you can't see an oceanic white tip everywhere, or a basking shark, or a whale shark, or a there's so many really cool sharks out there you want to see, and we don't even know all that much about sharks.

So many mysteries to discover.

Dolphins, yeah, done that.

They're also new animals.

I was going to ask you by a dolphin, but not by a shark.

There you go.

So we should really be like, wow, dolphins, let's stop supporting them and go for the sharks, right?

I was going to ask you, Stephen, because you've interacted with just so many animals on the land and in the oceans.

Would you characterize sharks as one of the species that you work with that we know the least about?

There's more to discover.

I would definitely say so.

I think, you know, if you think about any terrestrial iconic animal, then we're going to know pretty much the elementary parts to its life history.

And they will have been known for a very long time, probably for thousands of years.

And yet there are creatures under the sea that are household names, and yet we may know nothing about where they go, what they do, how they feed, how they breed.

The really exciting thing is it feels like now, and particularly listening to you two speaking, that we're entering into a golden era of understanding marine creatures.

And all of the kind of technology that you're talking about, Lucy, you know, it is now going to offer us a window into their world that we've never had before.

And all of a sudden, we are going to start knowing where these sharks go.

People used to think that basking sharks hibernated halfway through the year because we didn't know where they go.

Well, now we're going to start to understand that.

And what we are learning is inevitably extraordinary.

They're animals that are so rich in our cultural history, in myth, and in legend, and yet we don't know how they breed.

That's nuts.

And it is so, so exciting that now we're on the cusp of beginning to understand these things about them.

That the real scary thing for me particularly is that we may only be just discovering these things as we are about to lose the very animals themselves.

There are so many of these species that could easily go extinct within my lifetime.

Perhaps 250 million sharks being taken from the world's oceans every year, 73 million specifically for their fins.

And we don't yet know what the repercussions will be for an eradication of sharks, but it's going to be bad.

There will be huge knock-ons.

There always is whenever you remove an apex predator from an environment.

And that's not an experiment that I want to see the end game of.

Lucy, just the final thing.

I was talking to an environmentalist who said to me once, he said, the thing is, no one will try and save what they do not love.

So I wondered if you had just something that you would like to say to kind of, you know, infect more people with that love and fascination?

One of my favourite things about being a scientist is that I get to get close to and touch wild animals that most of you aren't allowed to because I have a permit.

And I care.

See, now all I'm remembering is you talking about being a pornographer.

Yeah, that's a good point.

Anyway, let's gloss past that.

And I think one of the reasons that I can care so much about this stuff is because I've seen it for myself, because I've been in the water with a blooming great big basking shark, shark which looks like an elephant kind of coming towards you.

You're kind of there snorkeling on the surface.

This thing's got its mouth open.

You're thinking, I could fit in that and it's coming right at you and you think, I hope it's going to move.

Should I move?

If I move, is it going to go the same way as me?

I could fit in there.

And then at the last minute it goes around you.

And that visceral experience, it really changes everything because all of a sudden it's not a shark just on a screen.

It's not this other thing that you don't necessarily know about.

It's something that you really, really care about.

So get out there, guys.

Get in the water.

And worst-case scenario, going back to the thing about being bitten at the beginning, if you do get bitten, you're gonna have an amazing scar.

It's not the worst case scenario, is it?

But actually, it is because I actually pulled some shark attack stats before this because I thought you might ask me about this.

And I think I found a record that was about 6,860-odd shark attacks on this, supposed to be like a global shark attack file.

And the fatalities, I think, was like 200 or something.

So, you're much more likely just to get annoyingly bitten and get a crook scar from it than you're going to die.

So, there is even just last year, there were 57 unprovoked or shark incidents, and five of those were fatal.

However, last year, a hundred people died from jellyfish things.

So, if this show has one message, it is kill the jellyfish.

Can we add dolphins to that?

I'm joking, joking, joking.

That was a joke.

Will it make the air there.

We asked our audience a question as well, and we asked them, what is the most frightening thing you have found in the sea?

Evelyn said, the swimming trunks I thought I was wearing.

I've got here Megalodon, and that's from Jason Statham, apparently.

My electronic car key fob.

Thank you very much to our panel, Steve Baxchall, Lucy Hawks, and Isla Hodgson.

Now, next week, we will be joining you from a car park in Leicester as we investigate ancient DNA.

Yep, that's it.

The car park where they found Richard III.

And as you know, Leicester Municipal Parking Services immediately had him clamped.

It's a two-hour maximum with no return, and he'd been there for five centuries.

That is some fine.

We'll see you next time.

Bye-bye.

Bye.

Hello, I'm India Raxon, and I just want to quickly talk to you about witches.

In this series from BBC Radio 4, simply titled Witch, I'm going to explore the meaning of the word today.

It is a twisting, turning rabbit warren of a world, full of forgotten connections to land and to power, lost graves, stolen words, and indelible marks on the world.

Because the story of the witch is actually the story of us all.

Come and find out why.

On Witch with me in Dirakerson.

Subscribe wherever you get your podcasts.

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