Human Footprint

(energetic music) (Rick) Theres very few things that all Australians will agree on.

(wings flapping) (frog thuds) But one of the things that will get general agreement is that cane toads are horrible and ugly... (projector slide changes) ...but, you know, youve really got to admire what the hell theyve achieved.

(Shane) This is Rick Shine, a legendary biologist and one of my science heroes.

When hes not waxing poetic about one of Australias most un-loved animals, you might find him out fishing.

(fishing line whirs) And keeping one eye on the water... (intense music) ...for these guys.

(mellow music) (tour guide) In the true Australian scientific description, hes referred to as a bloody big crocodile.

And if I tried to ride him like a horse, my tackle would tickle his back even on a cold day.

(Shane) Here in the Northern Territory, giant crocs are a source of pride.

Cane toads?

Not so much.

(Rick) You know, the conversation around the barbecue at night is, you know, "Bloody cane toads," and, "Theyre so ugly."

And it took me, you know, years before I actually looked at a cane toad and I thought, "Actually, thats a pretty damned attractive animal."

-Yeah.

-Uh, the eyes of a big female toad, you know, you can lose yourself in them.

Theyre gorgeous.

(mellow music) (Shane) Beautiful or not, cane toads are an invasive species in Australia.

Theyre native to wet tropical forests in the Americas.

And their Australian invasion began... ...with biocontrol.

(Rick) There was a World Congress of sugar cane growers in Puerto Rico in 1932.

Everyone got told about how fantastic these giant toads were at controlling insects in your sugar cane.

Mm.

At the time, Australias farmers were wrestling with a native pest called the greyback cane beetle.

(Rick) And it was only a year or two before an Australian had the brilliant idea that, "Hey, these giant toads can solve our problems as well."

(Shane) So, a young Aussie named Reg Mungomery went to Hawaii to get some toads.

Caught 101 toads, brought them back, released the babies, and the toads began their conquest of Australia.

(foreboding music) (Shane) The toads didnt stop the cane beetle, but they did make a lot more cane toads.

(water lapping) Because a single female can lay 20,000 eggs at a time.

They spread across Australia, eating whatever they could fit in their mouths... (tongue lapping) ...and poisoning native predators that tried to eat them.

(Rick) And it became clear that we had no way to stop them.

(energetic music) (Shane) Rick began studying cane toads in the early 2000s.

Until then, hed spent most of his career working on snakes.

(Rick) And Id been doing that very happily, uh, for about 20 years when the cane toad invasion appeared over the horizon.

And it would have been crazy not to move sideways a little bit and become a bit of a toad biologist.

(soft music) (Shane) Ricks work reveals how cane toads are reshaping Australian ecosystems.

(Rick grunts) (Shane chuckles) (Rick) You can tell by the thousands of bugs around your face that theres plenty here to eat.

-Oh yeah.

-Yep.

And this is the dry season.

In the wet season, the bugs are about a hundred times worse.

(Shane) Mm.

(Rick) Do you wanna try your toad-capturing technique, Shane?

(Shane) Yeah, lets see what we got here.

(intense music) (Rick) Nice grab.

(Shane) Took all the speed and strength I could muster to get her.

(Rick laughs) (quirky music) (soft music) Cane toads arrived at Ricks study site in 2005.

But these were not the same toads that Reg Mungomery released 70 years earlier.

In the early years, the cane toads spread at 10 to 15 kilometers a year.

(Rick) But then as they hit the drier country, they begin to go faster and faster and faster.

By the time they get to here, theyre moving at 50 to 60 kilometers a year.

(Shane) The toads that arrived in 2005 were built for speed.

(whooshing) (Rick) It is a genuine case of evolution within a human lifetime.

Are we talking about longer limbs?

Are we talking about metabolism?

Is it behavioral?

Very easy question to answer: everything.

Every characteristic we measure about cane toads, except maybe the number of legs, seems to differ.

That would be truly terrifying.

(energetic music) And the toads didnt just evolve fast; they revealed a whole new kind of evolution.

The toad showed us that evolution can occur through space as well as through time.

(Shane) Its a process Rick calls "spatial sorting."

As toads spread across Australia, the fastest individuals led the way.

And they bred with other fast-moving toads, because they were the only ones there at the edge of the invasion.

(Rick) We call that the Olympic village effect on the suspicion theres a bit of interbreeding in Olympic villages among athletes.

Some of the babies of those toads will inherit genes for stamina from mum and long legs from dad.

And so the next generation goes even further.

And thats a cumulative process.

(Shane) Its different from natural selection, because the fast-moving toads dont necessarily pass on more of their genes.

(Rick) Its simply that you end up with that kind of genes over there and those kind of genes over here.

Yeah, so, you basically-- you get the athletes on one end and the couch potatoes at the other end.

Absolutely.

(Shane) But as the toads swept across the continent, they werent the only ones evolving.

Rick and his team discovered an extraordinary adaptation in some of Australias snakes.

(Rick) The most remarkable change is that theyve evolved smaller heads.

And so if youve got a small head, you cant eat a really big cane toad.

(Shane) Thats a good thing, because if you cant eat a big cane toad, you cant get poisoned by one.

(whooshing) (mellow music) But other species havent proven so adaptable... (whooshing) ...and cane toads have had a profound impact on Australian ecosystems.

(Rick) You know, its not the toads fault.

But yet people are very inclined to say, "Heres the foreigner, heres the invader."

And if we go out the backyard and hit em all on the back of the head with a golf club tonight, well feel like were doing something to save Australian biodiversity.

(intense classical music) (ball whacks) (Shane) Hitting cane toads with golf clubs feels oddly specific.

(Simon) In terms of where toads love to live, the golf course is just a heaven for them.

(eerie music) (Shane) Meet Simon Middap.

(hip-hop music) He lives on a golf course but doesnt play golf.

His game... is cane toad busting.

Well, what are your personal feelings about cane toads?

-I dislike them intensely.

-Okay.

(Simon) So, I dont really like, you know, killing nature, but I have no problem with picking up a cane toad and disposing of it...humanely.

(Shane) Okay.

Humanely.

In other words, without the use of a nine-iron.

(Simon) So, weve come up with this thing, TTTT.

That stands for: Terrorize Toads on the Third Thursday.

Okay.

(Simon) We do it on the third Thursday because that made the name work.

(Shane) Okay.

The volunteer toad busters start their work when the golfers go home.

-(Western-style music) -(hawk cries) (Simon) And well see you back here at half past eight -with a bucket full.

-Okay.

-So, lets go and get em, eh?

-Good luck, everybody.

(Simon) Have fun.

(energetic music) (Shane) For a few hours each month, this is a dangerous place to be a toad.

(Simon) Theres another little one right beside him.

Look at that, two for one.

Dont let it get away.

(Shane) The most exciting part of the hunt?

The tally at the end of the night.

(Simon) 24, 25, 26, 27, 28, 29, 30, 31... You know, you get really excited when you get a thousand toads a night.

But youre never gonna do anything with the population just by catching the mature toads.

The process of catching toads is really so they can go back to the lab, they can get the toxin gland removed, and we can make these tablets.

Theyre called Bufo Tabs, which are things we put in the trap to catch tadpoles.

(Shane) But why are cane toad tadpoles drawn to bait made from cane toad poison?

Simple.

Because the tadpoles... (dramatic music) ...are cannibals.

(Rick) In Australia, a cane toads worst problem is another cane toad.

(Shane) Female toads infuse their jelly-coated eggs with toxins.

(Rick) And as the jelly coat breaks down, the poisons begin to diffuse out into the water.

And thats a signal for any cane toad tadpole in that pond to come roaring across and try to eat them cause you get rid of the competition.

(Shane) So, toad poison is the perfect bait for a tadpole trap.

(Rick) And as we speak, millions of cane toad tadpoles are being pulled out of natural water bodies across Australia.

(Simon) The purpose of really chasing the tadpoles is thats where you actually really do some numbers.

Last season, we caught over 250,000 tadpoles.

Whoa.

-A quarter million tadpoles!

-Yep.

(Shane) Removing tadpoles is a good way to control toads.

(hip-hop music) But Rick and his team realized they could also put the cannibals to work.

(Rick) How about if we stop tadpoles from transforming into baby toads, if we kept them as perpetual tadpoles.

(Shane) And heres where things start to sound like sci-fi.

(Rick) You can actually manipulate the genes inside the egg of a toad and knock out the gene that it needs to transform from the tadpole stage into the toad stage.

Oh.

Rick and his team did just that, creating tadpoles that never grow up.

Rick calls them "Peter Pans."

(Rick) They eat a lot more toad eggs than a normal taddy does -because theyre bigger.

-Mm-hm.

So, a pond full of Peter Pans is a deathtrap for new eggs.

(Rick) Toads can never breed there again until those tadpoles die of old age.

(mellow music) (Shane) Its a clever twist on biocontrol, turning a species against itself.

Peter Pan tadpoles havent been released in the wild yet.

But when they are, biocontrol might help solve a problem that biocontrol created.

The story of cane toads, you know, I think a lot of times its presented as a cautionary tale.

Is that still, like, a fair example, or is it out of date now?

Yeah, look, I think it was probably out of date even in the 1930s.

But there was too much political weight behind the push to bring in the toad.

(Shane) It turns out, even Reg Mungomery had his doubts.

(Rick) So, this is Reg Mungomery writing in the Cane Growers Quarterly Bulletin in 1934, "Such a project is not to be embarked upon lightheartedly, since a false step may have disastrous economic consequences through the upsetting of the whole biological balance."

And then a year later, they gave him a first class seat to Hawaii in a very nice ship.

And off he went and got the cane toads.

And did exactly the thing that he warned against.

-Yeah, Im afraid so.

-Okay.

Why?

I guess, is the question.

Oh, why do young men do anything, Shane?

Come on.

(laughing) (soft music) (Shane) Was it the desperation of an industry that brought cane toads here?

Or the impetuousness of youth?

Maybe a bit of both.

Either way, Rick doesnt want to follow in Reg Mungomerys infamous footsteps.

(Rick) Its taken decades to get to the point that Im comfortable we know enough about the system that we can carefully move forward.

I think maintaining that humility is a key to doing decent science and making responsible decisions.

(Shane) Australians could have turned their backs on biocontrol.

But they didnt.

Because fate dealt them another chance to get it right, this time with even higher stakes.