Transcriber: Asia Lindsay Reviewer: Denise RQ
This is poo.
And what I want to do today is share my passion for poo with you.
What you might find more fascinating
is the way these small animals deal with poo.
So this animal here
has a brain about the size of a grain of rice.
And yet, it can do things
you and I couldn't possibly entertain the idea of doing.
Basically, it all evolved to handle
its food source which is dung.
So the question is, "Where do we start this story?"
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 to make a living.
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 stuff.
The question is: "How do they deal with this material?"
And most dung beetles actually wrap it into a package of some sort.
It's made into a discrete ball,
but most of the time you won't see that
unless you're prepared to get dung under your fingernails
and rout through the dung itself,
you'll never see 90% 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's surface and the nest they make underground.
But fortunately for us,
10% of the species actually make a ball.
They roll away this ball from the dung source
and usually bury it at a remote place
away from the dung source.
They have a very particular behavior
by which they are able to roll their balls.
This is the very proud owner of a beautiful dung ball.
You can see it's a male — he's got hairy legs there.
He's clearly very pleased about what he's sitting on there.
But then he's about to become a victim of a vicious smash and grab.
(Laughter)
This is a clear indication that this is a valuable resource.
And 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.
This dung pat was actually
— well, it wasn't a dung pat
15 minutes before this photograph was taken —
we think it's the intense competition that makes the beetles
so well adapted to rolling balls of dung.
What you've got to imagine here
is this animal moving across the African veld.
Its head is down, it's walking backwards,
it's the most bizarre way to transport your food in any particular direction.
And, at the same time, it has 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.
There are two things I want you to be aware of,
the first is how it deals with this obstacle we've put in in its way.
See, 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 important thing,
because if you think about it, you're at the dung pile,
you've got this great big pile
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;
every now and then, they climb on top of the ball
and they take a look at the world around them.
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?
The most obvious one is to look at the sky.
So, we thought:
"What could they be looking at in the sky?"
and the obvious thing to look at is the sun.
A classic experiment here.
We moved the sun.
So 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.
(Laughter)
It makes up its mind
and heads back in the opposite direction.
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,
— so it's over on this side —
there is a north-south, huge pathway across the sky
of polarized light that we can't see.
But the beetles can see it.
So, how do we test that? Well, that's easy.
We get a great big polarization filter,
pop the beetle underneath it,
and the filter is at right angles to the polarization pattern in the sky.
The beetles 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.
Obviously, beetles can see polarized light.
So, what we've got so far
is, "What are beetles doing?" — they're rolling balls —
"How are they doing it?" — they're rolling them in a straight line—
"How are they maintaining a particular straight line?"
— they are 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?"
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.
What are they doing when they do this dance?
How far can we push them before they will reorientate themselves?
In this experiment here, 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 wrong direction.
It ends up going in exactly the opposite direction
that it wanted to go to in the first place.
And let's see what his reaction is,
as he is headed through 90 degrees here,
and when he ends up down here,
he's going to be 180 degrees in the wrong direction.
And see what its response is.
He does a little dance,
and turns around and heads back.
He knows exactly where he is going,
he knows exactly what the problem is,
and he knows exactly how to deal with it.
And the dance is a 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.
You'll see it in this video here. It's very obvious.
Every now and then,
when they climb on top of the ball
they wipe their face.
And you see him do it again.
Now what could be going on here?
Clearly the ground is very hot.
When the ground is hot, they dance more often.
And when they do this particular dance,
they wipe the bottom of their face.
We thought that it could be a thermoregulatory behavior,
maybe what they're doing is trying to get off the hot soil
and also spitting on their face to cool their head down.
So we designed a couple of arenas.
One was hot, one was cold;
we shaded this one, we left that one hot.
We were able to swap them around.
Then, we filmed them with a thermal camera.
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)
All we're interested in here is comparing
the temperature of the beetle against the background.
The background here is about 50°C.
The beetle itself and the ball
are probably around 30°C to 35°C.
This is a great big ball of icecream
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.
What's of interest here,
is that its little brain is quite cool.
But if we contrast now what happens in a hot environment,
— and look at this particular beetle,
look at the temperature of the soil —
it's up around 55°C to 60°C.
Watch how often the beetle dances.
Look at its front legs. They're roaringly hot.
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.
That was pretty interesting.
We were interested in the temperature of the legs,
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.
If you look over here,
with boots, they climb onto the ball far less often
than when they had no boots on.
We described these as cool boots.
It was a dental compound that we used to make them.
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.
This is called stilting.
It's a thermal behavior that you and I do when we cross the beach,
we jump onto a towel, or somebody else's towel,
"Sorry! I jumped onto your towel!"
then you scuttle across on 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.
They have a particular behavior that 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.
This is in slow motion.
But it's walking forward and it's dragging a pellet with it,
it's taking a pellet of dried dung with it.
This is a different species in the same genus,
but it has exactly the same foraging behavior.
So what's going on here?
One more interesting aspect
of this dung beetle's behavior that we found quite fascinating,
and that's it forages and provisions a nest.
Watch this individual here.
What he's trying to do is set up a nest.
He doesn't like his 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 dried dung pellets.
Notice the outward path, compared to the homeward path.
And compare the two.
By and large, you'll see that the homeward path
is far more direct than the outward path.
On the outward path, he's always on the lookout
for a new blob of dung.
On the way home,
— he knows where home is — and he wants to go straight there.
The important thing here, is that this isn't a one way trip.
As with most dung beetles, the trip here,
is repeated back and forth
between the provisioning site and the nest site.
Watch, you're going to see another South African crime
taking place right now!
(Laughter)
His neighbor steals one of his dung pellets.
This is a behavior called "path integration."
The beetle has a home spot,
it goes out on a convoluted path, looking for food;
when it finds food, it heads straight home,
it knows exactly where its home is.
Now there are two ways it could be doing that.
We can test what it's doing by displacing the beetle
to a new position when it's at the foraging site.
If it's using landmarks, it will find its home.
If it's using "path integration," it won't find its home,
it will arrive at the wrong spot.
Here it's using path integration.
It's counting its steps,
measuring the distance out in this direction,
it knows the bearing home,
it knows it should be in that direction.
If you displace it, it ends up in the wrong place.
Let's see what happens
when we put this beetle to the test
with a similar experiment.
Here's our cunning experimenter.
He displaces the beetle,
and now we have to see what is going to take place.
He doesn't like that piece. He rejects it.
He climbs onto the paper and is moved to a new position.
Now, what we've got is a burrow.
That's where the forage was.
The forager has been displaced to a new position.
If he's using landmark orientation
he should be able to find the burrow
because he should be able to recognize
the landmarks around it.
If he's using path integration
then it should end up in the wrong spot.
Over here.
So let's watch what happens
when we put the beetle through the whole test.
So there it is there.
He's about to head home,
and look what happens.
Shame.
It hasn't a clue.
It starts to search for its house,
in the right distance away from the food
but it's clearly completely lost.
So we know now that this animal
uses path integration to find its way around.
And the callous experimenter leaves at top left.
So what we're looking at here
are a group of animals that use a compass,
they use the sun as a compass to find their way around.
They have some sort of system for measuring that distance.
We know that these species here count their steps.
That's what they use as an odometer,
a step counting system
to find their way back home.
We don't know yet what dung beetles use.
What have we learned from these animals
with a brain the size of a grain of rice?
Well, we know they can roll balls in a straight line
using celestial cues.
We know that the dance behavior is an orientation behaviour,
and it's also a thermoregulation behavior,
and we also know that they use a path integration system
for finding their way home.
So, for a small animal,
dealing with a fairly revolting substance,
we can actually learn an awful lot from these behaviors,
doing things that you and I couldn't possibly do.
Thank you.
(Applause)