0:00:01 > 0:00:04BOTH: We are Dr Chris and Dr Xand van Tulleken.
0:00:04 > 0:00:07- And we're tracking down the most awesome...- ..incredible...
0:00:07 > 0:00:11BOTH: ..and epic things in the universe!
0:00:21 > 0:00:25BOTH: Come with us and discover unbelievable things
0:00:25 > 0:00:27that will Blow Your Mind!
0:00:28 > 0:00:32Blow Your Mind will be bringing you all the top experts
0:00:32 > 0:00:37in unbelievable stuff, from icebergs to elephants, spaceships to sharks.
0:00:37 > 0:00:41And, this week, it's all about amazing animals.
0:00:41 > 0:00:44So hold on to your brains, here's what's coming up.
0:00:44 > 0:00:47We're coming face-to-face with one of the most deadly
0:00:47 > 0:00:49animals in the ocean...sharks.
0:00:51 > 0:00:55Chris Packham discovers the sharks super sixth sense.
0:00:55 > 0:00:58Sends a shark to sleep.
0:00:58 > 0:01:03And meets some terrifying reef sharks at the bottom of the ocean.
0:01:03 > 0:01:06Earlier today we saw dolphins doing something absolutely
0:01:06 > 0:01:08incredible with their sixth sense.
0:01:08 > 0:01:10That really was incredible.
0:01:10 > 0:01:14Yes, but, not to be outdone by those dastardly dolphins,
0:01:14 > 0:01:17- step forwards - the shark. - The shark?! Step forwards?!
0:01:17 > 0:01:21- But it doesn't have feet! - Well, it's a figure of speech.
0:01:21 > 0:01:23Yeah, but imagine if sharks did have feet.
0:01:23 > 0:01:26Imagine them walking through your school, eating teachers
0:01:26 > 0:01:28and pushing into the lunch queue.
0:01:28 > 0:01:30Well, I guess that would be terrifying but they don't
0:01:30 > 0:01:34have feet. Sharks do, however, have something that humans don't have.
0:01:34 > 0:01:37Is it a super sixth sense?
0:01:37 > 0:01:42That's right, sharks have an incredible super sixth sense.
0:01:42 > 0:01:45Well, that's not easy to say.
0:01:45 > 0:01:49Chris Packham has travelled to the island of Bimini in the Bahamas.
0:01:49 > 0:01:51It's a hotspot for some awesome sharks.
0:01:53 > 0:01:57With me is scientist Eric Stroud.
0:01:57 > 0:02:01He's spent years studying sharks.
0:02:04 > 0:02:07Sharks are extremely successful predators.
0:02:07 > 0:02:12They can smell tiny quantities of blood over huge distances
0:02:12 > 0:02:17and follow minuscule vibrations of their prey in the water.
0:02:17 > 0:02:22But the shark sense that I want to investigate is very different.
0:02:22 > 0:02:26It's one that we humans have no experience of at all.
0:02:26 > 0:02:28Try to push them into here, yeah?
0:02:28 > 0:02:31Well, if we can get him against the fence, we have a better shot.
0:02:33 > 0:02:37Eric is going to demonstrate that sense with a strange experiment.
0:02:37 > 0:02:42But first, we need our baby lemon shark to stay nice and still.
0:02:42 > 0:02:44- OK.- Got it.- Got him.- Look at that.
0:02:49 > 0:02:53OK, so what we're going to do now is we're going to roll it over
0:02:53 > 0:02:57- and place it into tonic immobility. - Tonic immobility.
0:02:57 > 0:02:58Go on, explain that one.
0:02:58 > 0:03:01No-one is really sure why it happens, but
0:03:01 > 0:03:03when the sharks are inverted like this, they kind of go to sleep.
0:03:03 > 0:03:06Wow, he's just relaxed.
0:03:06 > 0:03:09- It's like yoga for sharks.- Indeed.
0:03:09 > 0:03:11And there's nothing to suggest that it's stressed.
0:03:11 > 0:03:13- I'm barely holding it.- Yeah.
0:03:13 > 0:03:15- I'm going to hand him to you, OK?- OK.
0:03:15 > 0:03:18And you just put your thumbs behind the pecs and just hold it.
0:03:20 > 0:03:21OK, ready?
0:03:21 > 0:03:24These things, obviously, I mean, it's stating the obvious,
0:03:24 > 0:03:28- but they can bite. What would be the damage?- A laceration, at this age.
0:03:28 > 0:03:31- You might need stitches, actually, from this little shark.- Oh.
0:03:31 > 0:03:35- So, if anything goes wrong, just let it go.- Let's do our experiment.
0:03:36 > 0:03:39Eric's experimental kit is really simple.
0:03:39 > 0:03:41Steel spoon.
0:03:41 > 0:03:45- And a magnet. Thanks, EJ. - I've been left holding the shark.
0:03:45 > 0:03:49I'm not sure whether that's an enviable position to be in or not.
0:03:49 > 0:03:51We have a strong magnet here that we're going to
0:03:51 > 0:03:54use for the experiment and it's a pretty powerful magnet
0:03:54 > 0:03:57and it'll attract the spoon out of my hand.
0:03:57 > 0:04:01Eric wants to show me how our shark reacts to the magnet.
0:04:01 > 0:04:05So, what we're going to do is put a blinder by the sharks eye
0:04:05 > 0:04:07so he can't see what I'm doing.
0:04:07 > 0:04:11'So the shark won't be able to see the magnet coming.'
0:04:11 > 0:04:13- OK, I'm going to put a blinder here. - Yeah.
0:04:13 > 0:04:14'But will he sense it?'
0:04:14 > 0:04:16- I'm approaching.- Oh!
0:04:18 > 0:04:20- That was a reaction. - Excellent response.
0:04:20 > 0:04:23- Wow, he jumped out of your hands! - He did.
0:04:23 > 0:04:27Whoa. I think he did sense it. That little shark does not like magnets.
0:04:27 > 0:04:29Let's see that again, in slow motion.
0:04:30 > 0:04:33And there he is sleeping, a little sharkey snooze. Whoa!
0:04:33 > 0:04:35He is out of there!
0:04:35 > 0:04:38Now, our little shark was completely unharmed but,
0:04:38 > 0:04:41he's so sensitive to the magnet, he jumped to get away from it.
0:04:41 > 0:04:43But why?
0:04:43 > 0:04:47Well, it's down to the fact that sharks have a sixth sense.
0:04:49 > 0:04:52Sharks have organs called the ampullae of Lorenzini,
0:04:52 > 0:04:53bit of a mouthful.
0:04:53 > 0:04:56And these are dark openings along the front of their noses.
0:04:58 > 0:05:01These are jelly filled tubes that are specially designed to
0:05:01 > 0:05:03sense the electrical current in the water
0:05:03 > 0:05:05and they sit just beneath the skin of the shark.
0:05:07 > 0:05:09They're extremely sensitive
0:05:09 > 0:05:12and able to pick up tiny electrical volts in the ocean.
0:05:14 > 0:05:17Now, we humans have nothing like this in our bodies.
0:05:17 > 0:05:20To us, this is completely alien.
0:05:20 > 0:05:25But why would a shark need an unusual superpower like this?
0:05:25 > 0:05:27It helps them to find food.
0:05:27 > 0:05:28They can locate the heartbeat of, say,
0:05:28 > 0:05:31a crab or stingray underneath the sand.
0:05:31 > 0:05:33When that animal is beating or it's moving,
0:05:33 > 0:05:37the muscles generate a very weak electromagnetic field
0:05:37 > 0:05:39and that's what their noses are gearing in on.
0:05:39 > 0:05:41We're, in a sense, simulating that.
0:05:41 > 0:05:45The movement of the magnet across the sharks nose induces that
0:05:45 > 0:05:46electromagnetic current.
0:05:46 > 0:05:49But we're just doing it many times greater than a stingray or a crab.
0:05:49 > 0:05:52- So it's like a sensory overload. - Exactly.- Hence the struggle.
0:05:52 > 0:05:53Exactly.
0:05:53 > 0:05:58OK, so at low levels, magnetism helps sharks to find their food
0:05:58 > 0:06:00but, at high levels, it scares them off.
0:06:00 > 0:06:02Well, it's a bit like our sense of sight.
0:06:02 > 0:06:04So, obviously, you need light to see,
0:06:04 > 0:06:07but too much light can be blinding.
0:06:07 > 0:06:10Now, before we find out how magnetism affects
0:06:10 > 0:06:13a group of reef sharks, Chris, what do you call a group of sharks?
0:06:13 > 0:06:15Is it like fish, you call them a school?
0:06:15 > 0:06:18Well, yes, but there's another collective noun for sharks.
0:06:18 > 0:06:19A shiver of sharks.
0:06:19 > 0:06:22Well, I'm not surprised, sharks certainly make me shiver.
0:06:22 > 0:06:25One man who's probably shivering in his boots right now is
0:06:25 > 0:06:28Chris Packham, who's about to come face-to-face with
0:06:28 > 0:06:30a shiver of very fierce looking reef sharks.
0:06:30 > 0:06:32Ooh!
0:06:33 > 0:06:36Chris and the researchers are heading to Triangle Rock,
0:06:36 > 0:06:40a well known gathering place for large, Caribbean reef sharks.
0:06:41 > 0:06:44And they've been joined by marine biologist Pat Rice.
0:06:46 > 0:06:50They're going to try an experiment putting a sharks magnetic sense up
0:06:50 > 0:06:55against their most powerful instinct - their urge to eat.
0:06:55 > 0:06:57Yeah, here they are, look. Caribbean reef sharks.
0:06:57 > 0:06:58Slap it on the water.
0:07:00 > 0:07:02- Oh!- Beautiful sharks, aren't they?
0:07:02 > 0:07:04They're stunning, absolutely stunning, aren't they?
0:07:04 > 0:07:06So, they're here. Let's get going.
0:07:06 > 0:07:07Wow.
0:07:14 > 0:07:16Stunning they may be,
0:07:16 > 0:07:21but to do this experiment, I'm going to have to jump in with that lot.
0:07:21 > 0:07:24I know they're only 2m but they look a little bit bigger than
0:07:24 > 0:07:25I imagined a 2m shark.
0:07:25 > 0:07:27Maybe it's the water, maybe it's acting as a lens
0:07:27 > 0:07:28and exaggerating their length.
0:07:31 > 0:07:36Pat now needs to set up the experiment, 8m down on the sea bed.
0:07:37 > 0:07:39So, what is the experiment?
0:07:39 > 0:07:42OK, so on the sea floor they're going to make two circles.
0:07:42 > 0:07:45One circle is going to be made out of powerful magnets,
0:07:45 > 0:07:47the other circle, which is going to look the same,
0:07:47 > 0:07:49is just made out of black bricks.
0:07:49 > 0:07:51And then, in the centre of each circle,
0:07:51 > 0:07:52they're going to put shark food.
0:07:52 > 0:07:55So they want to test whether or not the sharks are put
0:07:55 > 0:07:59- off by the magnetic field around the circle of magnets?- Exactly.
0:07:59 > 0:08:01Now, sharks are well known for their killer instinct
0:08:01 > 0:08:05and one of their most powerful senses is their sense of smell.
0:08:05 > 0:08:08Sharks have been known to detect a drop of blood in water
0:08:08 > 0:08:10at over 500m away.
0:08:10 > 0:08:12That's the length of five football fields.
0:08:12 > 0:08:15Wow, so we know that the sharks can definitely smell the food
0:08:15 > 0:08:17that's in the centre of both circles?
0:08:17 > 0:08:20Exactly, we know they can smell it but will they go for the food
0:08:20 > 0:08:23when it's surrounded by an invisible magnetic force field?
0:08:23 > 0:08:24Just watch this.
0:08:26 > 0:08:30On the sea floor, Pat and safety diver Vincent, are setting up
0:08:30 > 0:08:33the circle of magnets into which we will put our bait.
0:08:35 > 0:08:38We need to be sure that the sharks aren't simply
0:08:38 > 0:08:41deterred by a circle of black objects, so Pat has made
0:08:41 > 0:08:46a second circle of ordinary bricks covered in black tape.
0:08:47 > 0:08:51We'll put bait in the two circles and see what happens.
0:08:52 > 0:08:54The magnets are powerful.
0:08:54 > 0:08:56But will they repel the sharks?
0:08:56 > 0:08:59Wow, I do not fancy being Chris Packham at the moment.
0:08:59 > 0:09:00Yeah, me neither.
0:09:00 > 0:09:04But, did you know that they're developing magnets as shark
0:09:04 > 0:09:06- repellents on everything from fish hooks to surfboards?- Really?
0:09:06 > 0:09:08That is genius.
0:09:08 > 0:09:11Well, when I go swimming tomorrow, I'm going to make sure I bring this.
0:09:11 > 0:09:13Chris, I don't think there are sharks in our local swimming pool.
0:09:13 > 0:09:15Well, better safe than sorry.
0:09:15 > 0:09:18Hm, well, let's go and see how Chris Packham is getting on with
0:09:18 > 0:09:19those super scary reef sharks.
0:09:19 > 0:09:21BOTH: Watch out, Chris!
0:09:25 > 0:09:28Now, I'm told that the sharks in this spot have never yet
0:09:28 > 0:09:30attacked a human.
0:09:30 > 0:09:33But, to do this experiment, we need to deliberately tempt them
0:09:33 > 0:09:35in very close.
0:09:35 > 0:09:37We've arrived on the bottom.
0:09:37 > 0:09:41On this side is the ring of bricks, the placebo, if you like,
0:09:41 > 0:09:43and here on this side is the ring of magnets.
0:09:43 > 0:09:46So now all we've got to do is introduce the bait.
0:09:47 > 0:09:50OK, we've got sharks here, already they're coming in.
0:09:50 > 0:09:54Pat's got some bait here, some tasty tuna,
0:09:54 > 0:09:59we're going to try and fix this in the centre of each of the circles.
0:10:01 > 0:10:03We're in the water with hungry sharks
0:10:03 > 0:10:05and in our bare hands we've got some fish.
0:10:11 > 0:10:15'All of those sharks up by the boat will now be able to smell
0:10:15 > 0:10:17'the bait down here with us.'
0:10:17 > 0:10:19Here comes a shark, now.
0:10:20 > 0:10:22It's bypassed the magnets.
0:10:24 > 0:10:27And it's gone straight into the brick circle
0:10:27 > 0:10:28and it's taken the bait.
0:10:29 > 0:10:32'Now there's no bait in the bricks,
0:10:32 > 0:10:35'will they show an interest in the bait in the magnet circle?'
0:10:36 > 0:10:41Look at that, it turns as if it could sense that bait
0:10:41 > 0:10:43and turned away.
0:10:43 > 0:10:45It can tell there's food there,
0:10:45 > 0:10:49it must be able to see all of the other fish currently feasting on it.
0:10:49 > 0:10:52But it wouldn't go inside that ring of magnets.
0:10:57 > 0:11:01'Time to put fresh bait in the bricks, and I've barely had a
0:11:01 > 0:11:04'chance to retreat when a shark makes straight for
0:11:04 > 0:11:06'the brick circle again.'
0:11:08 > 0:11:11Look at that, it's a monstrous great animal.
0:11:12 > 0:11:16'But, so far, they haven't touched the bait in the magnets.
0:11:18 > 0:11:19'It's two nil.'
0:11:21 > 0:11:24It tweaked them and definitely flinched away.
0:11:26 > 0:11:29'And yet, they're clearly hungry.'
0:11:30 > 0:11:33Not me. No, not me.
0:11:35 > 0:11:38'We are down to our last piece of bait for the brick circle.
0:11:38 > 0:11:40'And it doesn't last long.'
0:11:41 > 0:11:44And it snaffled the food from the brick circle.
0:11:47 > 0:11:52'But there's no doubt, the magnets are repelling the sharks.'
0:11:52 > 0:11:54It seems almost confused by those magnets.
0:11:56 > 0:11:58But the bait remains in the circle.
0:12:00 > 0:12:02'Although undetectable by us,
0:12:02 > 0:12:08'in the sharks mind, our magnetic force field is overwhelming.
0:12:08 > 0:12:13'So strong, it even overrides the sharks primal urge to feed.'
0:12:14 > 0:12:16That was mind-blowing.
0:12:16 > 0:12:18Who would have thought these cold blooded killers could be
0:12:18 > 0:12:21put off by a magnetic field?
0:12:21 > 0:12:22Well, their sixth sense is just
0:12:22 > 0:12:25so sensitive that the magnets are too much for it.
0:12:25 > 0:12:28It would be like sitting hungry in front of your favourite sandwich,
0:12:28 > 0:12:31but every time you try and have a bite, you get an electric shock.
0:12:31 > 0:12:32Eventually, you'd give up.
0:12:35 > 0:12:36ELECTRIC SHOCK
0:12:40 > 0:12:43Yeah, eventually I would give up. And I'm really hungry.
0:12:43 > 0:12:45Well, don't worry about that, Chris,
0:12:45 > 0:12:48because here are some of the most jaw-dropping, mind-blowing
0:12:48 > 0:12:51moments from the amazing animals we've seen this week.
0:12:56 > 0:12:59We've seen super dogs with superpowers.
0:12:59 > 0:13:03And cat burglars that steal their neighbour's food.
0:13:03 > 0:13:06Dolphins that can recognise themselves.
0:13:07 > 0:13:09And sharks with a sixth sense.
0:13:10 > 0:13:13We've seen elephants that get emotional.
0:13:13 > 0:13:16Cheeky chimps that lie to each other.
0:13:16 > 0:13:19And cockatoos that can pick a lock.
0:13:19 > 0:13:23We've discovered how animals use their unbelievable senses,
0:13:23 > 0:13:28ingenious brains and social circles to dazzle us.
0:13:28 > 0:13:32And make us realise that we're not so different, after all,
0:13:32 > 0:13:36from these truly amazing animals.
0:13:36 > 0:13:38Wow, those are some awesome animals.
0:13:38 > 0:13:41And it's not just animals, next time we're going to be discovering
0:13:41 > 0:13:45even more awesome things. So join us to Blow Your Mind.