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Toxic cane toads are invading Taiwan. Conservationists race to contain warty amphibians.

Taiwan is currently fighting to contain an invasion of toxic cane toads (Rhinella marina). (Image credit: Shutterstock)
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Conservationists in Taiwan are racing to contain an invasion of non-native and highly toxic toads before the warty amphibians cause widespread damage to their new ecosystem. 

The cane toad (Rhinella marina) is a highly toxic species of toad native to the Americas, from the Central Amazon in Peru to the Rio Grande Valley in Texas. However, the species was also introduced across the globe in the early 20th century to various places, including the Caribbean, Australia and large parts of the Pacific, according to Amphibia Web (opens in new tab). Adult cane toads range from 3.5 to 5.9 inches (9 to 15 centimeters) in length and have yellow and brown skin covered with irregular warts. When threatened, cane toads release a milky-white toxin from their skin known as bufotoxin, which oozes from glands behind their eyes and is lethal to most animals. 

Researchers in Taiwan learned of a possible cane toad invasion at a farm in a small town in Taiwan's central mountain range, after a local resident shared photos of a cane toad online. After seeing the photo, researchers from the Taiwan Amphibian Conservation Society immediately came to the farm to investigate.

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"A speedy and massive search operation is crucial when cane toads are first discovered," Lin Chun-fu, an amphibian scientist at Taiwan's Endemic Species Research Institute, told French news agency AFP (opens in new tab). They reproduce rapidly, and "they have no natural enemies here in Taiwan," he added.

When the researchers arrived at the farm, they found 27 toads in the immediate vicinity. Since then, they have captured more than 200 cane toads in the area surrounding the town, according to AFP.

"I was shocked and worried when they found more than 20 [right away]," Yang Yi-ju, a toad expert at National Dong Hwa University who organized the search, told AFP. Cane toads are an extremely successful invasive species. They are only native to 14 countries but are now found in more than 40 countries, which has landed them a spot on the list of the 100 Worst Invasive Species overseen by the Invasive Species Specialist Group (opens in new tab), an international advisory body of scientists and policy experts. 

Cane toads are an extremely successful invasive species because of their ability to rapidly reproduce and avoid predation. (Image credit: Shutterstock)
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Female cane toads can lay up to 30,000 eggs at a time and can mate year-round, Live Science previously reported. Unlike other toads, which are exclusively predators, cane toads can also act as scavengers, so they always have plenty of food to eat. Without natural predators, their numbers quickly explode, and they can seriously damage ecosystems where they're introduced.

In the past, people deliberately released these toads in countries that were suffering from pest problems. For instance, in 1935, Australia introduced the toads to eat cane beetles (Dermolepida albohirtum) that were ravaging sugarcane fields. But while the toads successfully squelched the beetle infestations, the toad population quickly grew out of control. 

Researchers believe that a black market pet trade could have caused the recent Taiwan cane toad invasion. Cane toads have long been a popular pet in Taiwan and are also used in traditional medicines, according to AFP. But in 2016, the Taiwanese government banned the import of cane toads, which led people to breed and sell them illegally. The leading theory is that the invasive cane toads either escaped or were abandoned by one of these black market traders. 

The researchers also think the invasion may have started months ago and gone unnoticed until now. "Taiwanese farmers generally ignore toads and even look favorably at toads when they find them, because they help rid the land of pests and are also a good luck symbol," Yang told AFP. "It never occurred to them that this is an invasive species from a foreign land."

The researchers are now hopeful that they have contained the invasion, but it is too early to tell for certain. "Next spring during mating season is when we [will] truly know for sure if we have contained it," Yang told AFP.

Originally published on Live Science.

Harry is a U.K.-based staff writer at Live Science. He studied Marine Biology at the University of Exeter (Penryn campus) and after graduating started his own blog site "Marine Madness," which he continues to run with other ocean enthusiasts. He is also interested in evolution, climate change, robots, space exploration, environmental conservation and anything that's been fossilized. When not at work he can be found watching sci-fi films, playing old Pokemon games or running (probably slower than he'd like).