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  • Translator: Joseph Geni Reviewer: Morton Bast

  • This is poo,

  • and what I want to do today is share my passion

  • for poo with you,

  • which might be quite difficult,

  • but I think what you might find more fascinating

  • is the way these small animals deal with poo.

  • So this animal here has got a brain

  • about the size of a grain of rice, and yet it can do things

  • that you and I couldn't possibly entertain the idea of doing.

  • And basically it's all evolved to handle its food source,

  • which is dung.

  • So the question is, where do we start this story?

  • And it seems appropriate to start at the end,

  • because this is a waste product that comes out

  • of other animals, but it still contains nutrients

  • and there are sufficient nutrients in there

  • for dung beetles basically to make a living,

  • and so dung beetles eat dung, and their larvae

  • are also dung-feeders.

  • They are grown completely in a ball of dung.

  • Within South Africa, we've got about 800 species of dung beetles,

  • in Africa we've got 2,000 species of dung beetles,

  • and in the world we have about 6,000 species of dung beetles.

  • So, according to dung beetles, dung is pretty good.

  • Unless you're prepared to get dung under your fingernails

  • and root through the dung itself, you'll never see

  • 90 percent of the dung beetle species,

  • because they go directly into the dung,

  • straight down below it, and then they shuttle back and forth

  • between the dung at the soil surface

  • and a nest they make underground.

  • So the question is, how do they deal with this material?

  • And most dung beetles actually wrap it into a package of some sort.

  • Ten percent of the species actually make a ball,

  • and this ball they roll away from the dung source,

  • usually bury it at a remote place away from the dung source,

  • and they have a very particular behavior

  • by which they are able to roll their balls.

  • So this is a very proud owner of a beautiful dung ball.

  • You can see it's a male

  • because he's got a little hair on the back of his legs there,

  • and he's clearly very pleased about what he's sitting on there.

  • And then he's about to become a victim

  • of a vicious smash-and-grab. (Laughter)

  • And this is a clear indication

  • that this is a valuable resource.

  • And so valuable resources have to be looked after

  • and guarded in a particular way, and we think

  • the reason they roll the balls away is because of this,

  • because of the competition that is involved

  • in getting hold of that dung.

  • So this dung pat was actually -- well, it was a dung pat

  • 15 minutes before this photograph was taken,

  • and we think it's the intense competition

  • that makes the beetles so well-adapted

  • to rolling balls of dung.

  • So what you've got to imagine here is this animal here

  • moving across the African veld.

  • Its head is down. It's walking backwards.

  • It's the most bizarre way to actually transport your food in any particular direction,

  • and at the same time it's got to deal with the heat.

  • This is Africa. It's hot.

  • So what I want to share with you now

  • are some of the experiments that myself and my colleagues

  • have used to investigate how dung beetles

  • deal with these problems.

  • So watch this beetle,

  • and there's two things that I would like you to be aware of.

  • The first is how it deals with this obstacle

  • that we've put in its way. See, look, it does a little dance,

  • and then it carries on in exactly the same direction

  • that it took in the first place.

  • A little dance, and then heads off in a particular direction.

  • So clearly this animal knows where it's going

  • and it knows where it wants to go,

  • and that's a very, very important thing,

  • because if you think about it, you're at the dung pile,

  • you've got this great big pie that you want to get away from everybody else,

  • and the quickest way to do it is in a straight line.

  • So we gave them some more tasks to deal with,

  • and what we did here is we turned the world

  • under their feet. And watch its response.

  • So this animal has actually had the whole world

  • turned under its feet. It's turned by 90 degrees.

  • But it doesn't flinch. It knows exactly where it wants to go,

  • and it heads off in that particular direction.

  • So our next question then was,

  • how are they doing this?

  • What are they doing? And there was a cue that was available to us.

  • It was that every now and then they'd climb on top of the ball

  • and they'd take a look at the world around them.

  • And what do you think they could be looking at

  • as they climb on top of the ball?

  • What are the obvious cues that this animal could use

  • to direct its movement? And the most obvious one

  • is to look at the sky, and so we thought,

  • now what could they be looking at in the sky?

  • And the obvious thing to look at is the sun.

  • So a classic experiment here,

  • in that what we did was we moved the sun.

  • What we're going to do now is shade the sun with a board

  • and then move the sun with a mirror

  • to a completely different position.

  • And look at what the beetle does.

  • It does a little double dance,

  • and then it heads back in exactly the same direction

  • it went in the first place.

  • What happens now? So clearly they're looking at the sun.

  • The sun is a very important cue in the sky for them.

  • The thing is the sun is not always available to you,

  • because at sunset it disappears below the horizon.

  • What is happening in the sky here

  • is that there's a great big pattern of polarized light in the sky

  • that you and I can't see. It's the way our eyes are built.

  • But the sun is at the horizon over here

  • and we know that when the sun is at the horizon,

  • say it's over on this side,

  • there is a north-south, a huge pathway across the sky

  • of polarized light that we can't see

  • that the beetles can see.

  • So how do we test that? Well, that's easy.

  • What we do is we get a great big polarization filter,

  • pop the beetle underneath it, and the filter is at right angles

  • to the polarization pattern of the sky.

  • The beetle comes out from underneath the filter

  • and it does a right-hand turn,

  • because it comes back under the sky

  • that it was originally orientated to

  • and then reorientates itself back

  • to the direction it was originally going in.

  • So obviously beetles can see polarized light.

  • Okay, so what we've got so far is,

  • what are beetles doing? They're rolling balls.

  • How are they doing it? Well, they're rolling them in a straight line.

  • How are they maintaining it in a particular straight line?

  • Well, they're looking at celestial cues in the sky,

  • some of which you and I can't see.

  • But how do they pick up those celestial cues?

  • That was what was of interest to us next.

  • And it was this particular little behavior, the dance,

  • that we thought was important, because look,

  • it takes a pause every now and then,

  • and then heads off in the direction that it wants to go in.

  • So what are they doing when they do this dance?

  • How far can we push them before they will reorientate themselves?

  • And in this experiment here, what we did was we forced them

  • into a channel, and you can see he wasn't

  • particularly forced into this particular channel,

  • and we gradually displaced the beetle by 180 degrees

  • until this individual ends up going in exactly the opposite direction

  • that it wanted to go in, in the first place.

  • And let's see what his reaction is

  • as he's headed through 90 degrees here,

  • and now he's going to -- when he ends up down here,

  • he's going to be 180 degrees in the wrong direction.

  • And see what his response is.

  • He does a little dance, he turns around,

  • and heads back in this. He knows exactly where he's going.

  • He knows exactly what the problem is,

  • and he knows exactly how to deal with it,

  • and the dance is this transition behavior

  • that allows them to reorientate themselves.

  • So that's the dance, but after spending many years

  • sitting in the African bush watching dung beetles on nice hot days,

  • we noticed that there was another behavior

  • associated with the dance behavior.

  • Every now and then, when they climb on top of the ball,

  • they wipe their face.

  • And you see him do it again.

  • Now we thought, now what could be going on here?

  • Clearly the ground is very hot, and when the ground is hot,

  • they dance more often, and when they do this particular dance,

  • they wipe the bottom of their face.

  • And we thought that it could be a thermoregulatory behavior.

  • We thought that maybe what they're doing is trying to

  • get off the hot soil and also spitting onto their face

  • to cool their head down.

  • So what we did was design a couple of arenas.

  • one was hot, one was cold.

  • We shaded this one. We left that one hot.

  • And then what we did was we filmed them with a thermal camera.

  • So what you're looking at here is a heat image

  • of the system, and what you can see here emerging

  • from the poo is a cool dung ball.

  • So the truth is, if you look at the temperature over here,

  • dung is cool. (Laughter)

  • So all we're interested in here is comparing the temperature

  • of the beetle against the background.

  • So the background here is around about 50 degrees centigrade.

  • The beetle itself and the ball are probably around about

  • 30 to 35 degrees centigrade,

  • so this is a great big ball of ice cream

  • that this beetle is now transporting across the hot veld.

  • It isn't climbing. It isn't dancing, because

  • its body temperature is actually relatively low.

  • It's about the same as yours and mine.

  • And what's of interest here is that little brain is quite cool.

  • But if we contrast now what happens in a hot environment,

  • look at the temperature of the soil.

  • It's up around 55 to 60 degrees centigrade.

  • Watch how often the beetle dances.

  • And look at its front legs. They're roaringly hot.

  • So the ball leaves a little thermal shadow,

  • and the beetle climbs on top of the ball

  • and wipes its face, and all the time it's trying to cool itself down,

  • we think, and avoid the hot sand that it's walking across.

  • And what we did then was put little boots on these legs,

  • because this was a way to test if the legs

  • were involved in sensing the temperature of the soil.

  • And if you look over here, with boots they climb onto the ball

  • far less often when they had no boots on.

  • So we described these as cool boots.

  • It was a dental compound that we used to make these boots.

  • And we also cooled down the dung ball, so we were able

  • to put the ball in the fridge, gave them a nice cool dung ball,

  • and they climbed onto that ball far less often

  • than when they had a hot ball.

  • So this is called stilting. It's a thermal behavior

  • that you and I do if we cross the beach,

  • we jump onto a towel, somebody has this towel --

  • "Sorry, I've jumped onto your towel." --

  • and then you scuttle across onto somebody else's towel,

  • and that way you don't burn your feet.

  • And that's exactly what the beetles are doing here.

  • However, there's one more story I'd like to share with you,

  • and that's this particular species.

  • It's from a genus called Pachysoma.

  • There are 13 species in the genus, and they have

  • a particular behavior that I think you will find interesting.

  • This is a dung beetle. Watch what he's doing.

  • Can you spot the difference?

  • They don't normally go this slowly. It's in slow motion.

  • but it's walking forwards,

  • and it's actually taking a pellet of dry dung with it.

  • This is a different species in the same genus

  • but exactly the same foraging behavior.

  • There's one more interesting aspect of this

  • dung beetle's behavior that we found quite fascinating,

  • and that's that it forages and provisions a nest.

  • So watch this individual here, and what he's trying to do

  • is set up a nest.

  • And he doesn't like this first position,

  • but he comes up with a second position,

  • and about 50 minutes later, that nest is finished,

  • and he heads off to forage and provision

  • at a pile of dry dung pellets.

  • And what I want you to notice is the outward path

  • compared to the homeward path, and compare the two.