Source: US National Invasive Species Information Center
Where do red imported fire ants come from?
Red imported fire ants (RIFA) are native to South America, where a variety of insects, spiders and birds prey on them and help to keep their populations in check. When they spread beyond this region, however, they’re much harder to control.
The first red fire ants to establish outside of their home range are believed to have arrived in Mobile, Alabama, in the 1930s. It’s thought that soil containing the ants was used as ballast for the ships arriving at the port city, allowing the ants to gain a foothold in a new continent.
Since then, the ants have spread across much of the USA, where it is estimated they cost around $6 billion to deal with every year. Genetic studies of the ants have shown that the subsequent spread of the ant to countries including China, Australia and New Zealand all come from North American populations, likely through the shipping of contaminated goods.
What are the impacts of red imported fire ants?
Red imported fire ants have a painful sting, which they use to defend themselves and their colony. If a human or animal accidentally disturbs them, the ants will respond by injecting venom into the unfortunate victim.
For larger animals, including humans, a single sting is about as painful as a bee’s, and while it might cause a pustule to form around the wound it is otherwise harmless. However, in some people the sting can cause a severe allergic reaction which can be life-threatening if not treated quickly.
Smaller animals, such as birds, lizards and some mammals, are at much greater risk of serious harm from the ants, especially if the insects feel threatened. This can encourage them to release pheromones that cause them to swarm and sting in a group which can prove fatal.
The most prolific impacts, however, tend to come as the result of their relationship on much smaller animals.
Suzanne Ryder, the Senior Curator in Charge who looks after the Natural History Museum’s ant collections, says, ‘Arthropods like spiders and other ant species are a big source of food for the red imported fire ant.’
‘While some ant species can live alongside them, many can’t, and this means the fire ants have quite an impact on the ecology of the areas they live in.’
This can prove especially problematic if the ants move onto farmland. As well as threatening the wildlife which live there, they can also eat seeds and damage the shoots of young plants, leading to reduced yields for farmers.
Fire ants are also able to live in urban areas as they can build their nests under concrete and other artificial materials, which can cause structural issues with buildings. They are also known to attack electrical equipment after being shocked.
The collective impact of the ant meant that in the year 2000, the International Union for the Conservation of Species declared it one of the 100 worst invasive species in the world.