With the rise of globalization, long-distance commutes and commerce have increased drastically. This along with other factors have increased the frequency of introduction of invasive or non-native species to aquatic and terrestrial ecosystems around the world. Invasive species refer to the plants and animals that evolve in one location and are introduced into another location through various means.
Such species travel through the oceans by swimming or hitching a ride on ships, boats, logs, or even leaves. Upon arriving at a new location, several things can happen. A species can find a new habitat harsh and eventually die off, it can adapt to the environment and have a little environmental impact, or it can take over, thereby causing harm to the naturally existing wildlife in a variety of ways.
One famous example of animal stowaway is the conquest of North America’s Great Lakes by zebra mussels in 1988. Native to the Caspian and Black Seas, the mussels were transported by a cargo ship from their source destination. Since its introduction, the tiny creatures multiplied uncontrollably, starving out a huge population of native mussel of the Great Lakes and causing devastating ecological damage and economic loss. These mollusks have now spread from Canada to Mexico and are considered a great nuisance species. A huge sum of money is spent annually to control their numbers.
The recent introduction of the common Asian toad called Duttaphrynus melanostictus to Madagascar has instigated fears that the toxic amphibian could devastate the island’s already beleaguered endemic fauna, including lemurs and several other animals found nowhere else on earth. Ever since their introduction, the toads have been gradually spreading across the island.
The fears have been now confirmed by the recent findings by a research team led by Ben Marshall, a masters student at the Bangor University. The researchers now confirmed that virtually all predators native to Madagascar are highly sensitive to the toad’s toxins. This means that the toad’s skin is laced with a deadly toxin that kills almost everything that tries to eat the animal. The study was published in the journal Current Biology on June 4, 2018.
The potent toxins called bufadienolides secreted by the amphibian disrupt the flow of sodium and potassium in cell walls, something that is very crucial for the functioning of muscles, and particularly the heart.
“Animals that are not resistant to the toads that take a mouthful of toad can die extremely quickly from heart failure,” says Wolfgang Wüster, a herpetologist at Bangor University in Wales. He adds, “Madagascar has been isolated for tens of millions of years. It’s never had toads. Why would the local animals be resistant to toads? We always expected them to be sensitive. But now we have much better evidence that that’s really the case.”
It is probably too late to remove the toads from Madagascar as their numbers have increased vigorously and there’s no good way to easily find and kill them. However, the study may help researchers in the island nation to take measures to protect certain species or sites from the invasive species.
Toxic toads are an invasive species in many places across the globe. Take Cane toads, for example. They have been spreading across northern Australia for several years now, causing drastic declines of species such as quolls and snakes. This event is well-studied, and it has been found that a lot of species had been affected by it.
Some other examples of invasive species include the gypsy moth called Lymantria dispar in eastern North America, the Eastern grey squirrels in Europe, and the nutria (Myocastor coypus) in North America.
Governments are now focusing on how to handle a ship ballast to combat invasive species. New laws in several nations require ships to exchange their ballast water while out in the ocean or treat it to kill stowaway species prior to being released.