In some cases, an invasive animal can really take over a country or island's ecosystems. Such is the threat in the large island nation of Madagascar, where invasive Asian toads are set to encroach upon the native wildlife, as a new report suggests. It also notes that the frogs are already spreading uncontrollably in the eastern part of the island. In yet another example of what can happen if biodiversity changes in vast ways, experts say this poses a direct threat to human health and the economy.

In the latest study, a team of international experts examines the feasibility of a wide-scale eradication program on the 226,657 square-mile nation (nearly the size of Chile), following a series of successful, controlled field tests. Based on their findings, scientists warn there is a "diminishing window of opportunity."

The Asian toad (Duttaphrynus melanostictus) is thought to have arrived in Madagascar's port city of Toamasina via freight containers travelling from Southeast Asia between 2007 and 2010.

"The Asian toad can spread across most habitats with no obvious barriers. However, it is currently restricted to about 110 square kilometers, which gives us hope that we can contain it, but only if we act now," James Reardon, co-author of the recent report and an eradication expert with New Zealand's Department of Conservation, explained in a news release.

Researchers estimate that a population of about four million toads has been established around the port city of Toamasina and is expanding outward from that area at a rate of two kilometers per year.

"If the toads become established in the Pangalanes Canal system -- one of the longest manmade canals in the world -- eradication will no longer be an option, and they will likely cause ecological damage similar to that of the Cane toad in Australia," Reardon added.

The toads -- also known as the Javanese, black-spectacled or black-spined toad -- are long-living, rapid breeders that produce up to 40,000 eggs a year. They secrete a milky toxin that is poisonous to native birds, mammals and snakes that prey on the toads.

"Madagascar is a wildlife haven, containing some of the planets richest biodiversity, including lemurs," Christian Randrianantoandro, co-author of the recent report from Madagasikara Voakajy, said in the release. "Without swift action, we expect the effects of this toad to be devastating. It could disrupt food chains and cause native predators, prey, and competitors to decline or even go extinct." (Scroll to read more...)

Asian toads have also had an impact on human health, with reported cases of death and cardiac arrest in Laos. The danger of consuming these particular toads is also of particular concern in Madagascar, where rural populations regularly include toads in their diet.

Scientists also warn that a decrease in predators due to toad poisoning would lead to an increase in rat populations. In turn, this could have an impact on human health through the spread of diseases, such as the plague.

Biosecurity concerns have also impacted Madagascar's international trade, especiall since Australia's government identified the Asian toad as a high-risk "Unwanted Organism."

Therefore, scientists recommend a complete eradication of the toads from Madagascar, which would "eliminate all possible ecological, economic and social impacts the toads may have ... with no long-term cost implications other than ongoing biodiversity improvements."

Researchers have been testing small-scale eradication trials since January, and have found success with methods involving manual removal, trapping with drift fences, tadpole trapping, removing the toxins from the toads and using them as a lure, and spraying them with citric acid.

However, eradication of an entire amphibian species has never been achieved on a large scale, so success would depend on three things: detection methods that would pick up every animal across the entire area; toads being captured and removed faster than they breed, and no further toads being brought into the country.

"Considering the broad range of biological and economic negative impacts that are expected from this toxic toad, future generations will be furious, should we not make an eradication effort now, while there is still a chance of success," Chris Raxworthy, co-author and herpetologist and associate curator at the American Museum of Natural History, added in the release. "We do not want to look back twenty years from now and wonder what Madagascar would be like if we had addressed this issue properly."

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