The Asian toad (Duttaphrynus melanostictus) is a toxic and invasive species recently arrived in Madagascar. Experts fear ecological impacts similar or worse to those wrought by the cane toad in Australia. Toamasina, Madagascar. January 2016. Photo: James Reardon.
Toamasina, Eastern Madagascar—International experts have released a report detailing the risks and immediate measures necessary to deal with the plague of invasive toxic Asian toads (Duttaphrynus melanostictus) currently spreading in Eastern Madagascar. Following serious international concern over the predicament of Madagascar’s precious and unique wildlife, including an estimated 800 endemic frog species, the Eradication Feasibility Report stresses the urgent need to field test methods to address this environmental catastrophe.
“Madagascar is a wildlife haven, containing some of the planets richest biodiversity, including lemurs,” said Christian Randrianantoandro of Madagasikara Voakajy, and a coauthor of the report. “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.”
According to the report, the Asian toad arrived in the port city of Toamasina, probably between 2007 and 2010. Using genetic analyses, researchers have found that the toads are most similar to populations in mainland Southeast Asia. The exact origin and method of introduction is still unknown. The core area of the current toad distribution, where the toads are most likely to have originated from, includes the Ambatovy Mine Processing Plant, which represents the dominant economic activity in this area.
“The Asian toad can spread across most habitats with no obvious barriers. However, it is currently restricted to about 110 km2, which gives us hope that we can contain it, but only if we act now,” said James Reardon an eradication expert with New Zealand’s Department of Conservation, and coauthor. “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.”
In addition to its effects on wildlife, the toad could also impact human health. In Laos for example, the Asian Toad has poisoned and killed people who consumed it, and in Madagascar, where edible frogs are a common component of the diet in many rural areas, there is considerable risk of human poisoning through consumption. The Asian toad could also increase the incidence of rat-vectored diseases including plague, should rat populations increase due to a decline in their natural predators such as snakes which are likely to decline with the arrival of the toads. International trade from Madagascar could also be impacted—the Queensland Government in Australia, for example, has already identified the Asian toad as a high-risk “Unwanted Organism” thus putting constraints on importation of goods originating from locations with the toad and poor biosecurity.
Since Jan. 2016, researchers have been working with local technicians, students and communities to test capture and trapping techniques, and possible chemical control methods. Although initial reports are promising, the team has found a diminishing window of opportunity during which eradication may still be feasible. Success will require immediate technical and financial support, as well as the development of in-country eradication capacity.
The situation is even more complicated because of the lack of enforced border biosecurity measures in Madagascar. The study’s authors argue that the cost of eradication can only be justified if the probability of reinvasion has been reduced through an improvement in biosecurity policy, resourcing and enforcement at Madagascar’s borders.
“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,” said Chris Raxworthy, herpetologist and associate curator at the American Museum of Natural History, and coauthor. “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.”
The authors of this report are: Dr. James T. Reardon (New Zealand Department of Conservation), Prof. Chris Raxworthy (American Museum of Natural History, Mr. Pete McClelland (Eradication contractor), Dr. Fred Kraus (University of Michigan, Ann Arbor) and Mr. Christian Randrianantoandro (Madagasikara Voakajy).