Science, Tech & Environment

In Madagascar, invasive toads are threatening rare wildlife and frightening locals

Common Asian Toad.jpg

The Asian common toad has lived side by side with other creatures in its native habitat for millennia. But introduced into a new location, the mildly poisonous species can wreak havoc on unsuspecting predators. That's why scientists were worried to find the toad recently in Madagascar, home to some of the world's most unique and highly-endangered wildlife.

Credit:

Brian Gratwicke/Flickr

Something isn’t quite right along a bumpy dirt road on the east coast of Madagascar.

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Residents of the village of Farafaty cook skewers of meat over an open fire while a soundtrack of Malagasy music emanates from a small shop — behind a bed of chirps and croaks from the surrounding woods and wetlands.

It’s a typical scene here, but if your ears are attuned to it, you can hear an interloper amid the din — the low croaking sound of the Asian common toad.

Madagascar doesn’t have any native toads, so local resident Jean Francois knew something was wrong the first time he saw one.

“We were surprised and confused” when the toads first arrived, Francois says. “People still don’t know why they’ve come to Madagascar.”

The prevailing theory is that the toads hitched a ride on a container ship from Asia. Ground zero for the invasion is Toamasina, Madagascar’s largest international port, and Farafaty is just a few miles away.

The toads first showed up in the courtyard of the home of Farafaty chief Razana Mahinina about eight months ago. He says he’s been afraid for his children ever since.

“If they play with them, they could get sick,” Mahinina says. “I’ve heard the toads can kill people. So when I see the toads, I kill them and bury them.”

You don’t have to look very hard to find one. A toad hunt led by researchers from the Madagascar Fauna and Flora Group bags its first quarry just a few feet from Mahinina’s house. Two researchers from the Madagascar Fauna and Flora Group find one almost right away, sitting on a plastic bag. Then another, and another.

As soon as you know what you’re looking for, it seems that they’re everywhere.

When researcher Bernard Iambana Richardson catches one, it’s about the size of a fist — brown and bumpy. But its most striking characteristic, the thing that has people here worried for their children, is a pair of small sacks on its back.

Iambana Richardson presses one of the sacks with a stick and a milky white liquid oozes out. It’s mildly poisonous, a common feature in toads, and a deterrent to predators in its natural habitat — no real threat to people, but you wouldn’t know it from local news reports. One said the toads are biting people and that they even surrounded a cow and killed it.

But as exaggerated as these reports might be, the toads do pose a real risk to Madagascar’s environment.

Jonathan Kolby, a doctoral candidate who studies toads at the University of Queensland in Australia, says there have already been reports of some endemic boa snakes dying after trying to eat the toads. And he says they could also pose a threat to birds and mammals that might prey on them.

Kolby is keeping a close eye on Madagascar because of what happened when a very similar species arrived in Australia some 80 years ago. There, cane toads were imported from Latin America by farmers hoping to control a scourge of beetles. The effort failed, but from just a few dozen individuals the toxic toads quickly spread across all of northern and eastern Australia, causing local extinctions of native animals in their path.

The cane toads are still taking their toll today, and Kolby worries about a similar situation unfolding in Madagascar, because, he says, like those in Australia, the Asian toads can adapt to a wide variety of habitats.

“That virtually means they can spread across the island,” Kolby says.

And that could be very bad news here.

Madagascar is home to thousands of native plants and animals that are found nowhere else on earth — things like lemurs, chameleons and giant baobab trees, all of which developed during the giant island’s millions of years of isolation from the rest of the world’s land masses. But in recent decades some 90 percent of the country has been deforested, so what’s left of its unique natural ecosystem is highly endangered and vulnerable to disturbances from invasive species.

So far, the toad outbreak here is confined to a roughly 12-mile radius around Toamasina. And scientists are hatching a plan to eradicate the amphibians, tied to their next breeding season later this year.

“It’s going to be a massive effort,” says Maya Moore of Madagascar Fauna and Flora Group, “because we’re dealing with all kinds of different terrain and private property and areas that are difficult to access.”

Moore says authorities will try to remove egg masses, fence off potential breeding grounds and poison eggs and tadpoles with nontoxic chemicals like citric acid and caffeine. They’ll also need to enlist local people to help kill adult toads — a task for which it should be no problem finding volunteers.

“We have no use for them,” says Alene, a 22-year-old Farafaty resident. “I’m afraid of the toads. They are ugly and poisonous. ... If there’s something we can give them to kill them, we should do that.”

  • Captured.JPG

    Asian common toads started showing up in the tiny town of Farafaty, Madagascar, about eight months ago and have since become common in the area. The frog has two small sacs on the back of its neck that exude a slightly poisonous liquid when squeezed, a natural deterrent to predators. The poison poses no real threat to humans but can kill unsuspecting predators.

    Credit:

    Bobby Bascomb

  • Family.JPG

    The toads first showed up in the courtyard of the home of Farafaty chief Razana Mahinina about 8 months ago, and he says since then he’s been afraid for his children. “If they play with them they could get sick,” Mahinina says. “I’ve heard the toads can kill people. So when I see the toads, I kill them and bury them.”

    Credit:

    Bobby Bascomb

  • map15july2014_with_Ambatovy_pointsJPEG.jpg

    This map created by Madagascar Fauna and Flora Group shows sites (in red) around the port city of Toamasina where the invasive Asian toads have been found.

    Credit:

    Madagascar Fauna and Flora Group

  • Gmap2.png

    The village of Farafaty is just outside Toamasina, Madagascar’s largest international port, on the country's east coast (yellow star). Madagascar's unique animals and plants have all developed in isolation since the island separated from the Indian plate more than 80 million years ago. That isolation, combined with widespread deforestation, makes it vulnerable to disruption from invasive species like the Asian common toad.

    Credit:

    Google Maps