The discovery in Japan of at least two colonies of aggressive fire ants thought to have been imported from China has triggered alarm among local authorities, with wildlife experts warning that the infestation needs to be stamped out immediately if the insects are to be prevented from gaining a foothold.
Should the ants evade the extermination teams that have been dispatched to locate and destroy their colonies, the experts say they could have a severe impact on native flora and fauna – pointing to numerous other examples of imported species playing havoc with Japan’s indigenous wildlife.
The first swarm of fire ants was discovered on May 26, in a shipping container that had arrived in Amagasaki from Japan’s port of Kobe. The shipment, which originated in the Chinese province of Guangdong, had been unloaded at the port six days previously. A visual inspection of the container at the port had failed to notice the ants’ presence.
The container was returned to Kobe port to be sterilised and officials of the Environment Ministry moved quickly to quell concerns, using a chemical disinfectant to kill the creatures.
In a statement, a ministry official insisted, “It is unlikely the fire ants have settled in the area and are breeding.”
Five days later, officials were forced to revise that claim when a second colony of ants was discovered in the yard where containers are stored at Kobe port.
They emphasised that because the nearest homes are more than 2km from where the ants were found, there was no danger to the public. Native to South America, fire ants can grow up to 6mm long, are aggressive and their bite can induce anaphylactic shock and, in extreme cases, death. As their name suggests, a single ant’s bite produces a severe burning sensation and swarms of the insects can cause extensive injuries to humans and other animals.
“The problem is that ants, spiders and other sorts of insects are small and can easily be carried around the world on cargo ships,” said Kevin Short, a professor in the environmental education department at the Tokyo University of Information Sciences.
“That means they are usually identified in port areas initially, but they can spread very quickly and we will only really know if they have managed to evade the effort to eliminate them when they are found somewhere else as well,” he said. “And at that point, it will be extremely hard to contain them any more.”
And Short believes that fire ants might ultimately become more of a problem for Japan than the venomous redback spiders that arrived from Australia more than a decade ago and have since set up breeding colonies in parts of the country.
“The redbacks have largely been contained and tend to hide in out-of-the-way places, like drains, so they are not so much of a nuisance,” he said. “But fire ants can spread across large areas very rapidly and survive in a far wider range of habitats.”
And, as well as the impact on humans, Short estimates that fire ants may very well have a calamitous effect on the smaller and less aggressive species of Japanese ants.
He points to several precedents, such as the largemouth bass, which was introduced deliberately as a game fish in 1925 but has since gone on to decimate local freshwater fish competing for food and space. Listed as one of the top 100 worst invasive species in Japan, it is presently prohibited to import, transport or keep the fish in Japan.
On the island of Chichijima, 1,000km south of Tokyo, the green anole lizard has similarly all but wiped out some indigenous insects after first brought to the island by the US military shortly after the second world war. Worryingly, the lizards – which are a mere 15cm long and appear to pose little threat – have been found on more islands in the Ogasawara archipelago, which was recognised as a UNESCO Natural World Heritage site in 2011.
There are thought to be millions of lizards on Chichijima and nearby Hahajima, where they arrived in the 1980s.
Both the Celastrina ogasawaraensis, a butterfly designated as a nationally protected species, and the indigenous Ogasawara dragonfly have been driven to the brink of extinction by the lizards. The plight of local insect life has had a knock-on effect for other unique species of birds and bats.
Elsewhere, American bullfrogs imported as part of a plan to export frog meat to Europe managed to escape their enclosures and have multiplied rapidly, while Mississippi crayfish brought in for the frogs to eat also managed to get free.
Snapping turtles – which can grow up to 15kg and have a beak strong enough to take a person’s finger off – have been dumped by people who bought them as pets and then could not take care of them. Red-eared slider turtles are found in the wild for the same reason, along with American raccoons.
“Those are just some of the examples of non-native creatures that have been let loose here and the consequences of that,” said Short. “But having fire ants here would be a major problem.”