Red-imported fire ants are already infamous among ants for their aggressive behavior and painful bites. Unfortunately, according to a recent study, it seems they are getting even bigger, more aggressive, and venomous in coastal areas. Flooding and the consistently rising sea levels seems to be triggering a physiological and behavioral adaptive response in red-imported fire ants that makes them breed larger and more aggressive ants. This spells bad news for Louisiana, as after the South American species was accidentally brought over to the United States via Alabama in the 1920s, they spread quickly across the south, their numbers proliferating throughout the state of Louisiana over the last century. Add to its massive red-imported fire ant population the fact that Louisiana is becoming increasingly flood-prone and faces the highest rate of relative rising sea levels and things begin to look bleak indeed.

Linda Hooper-Bui, a wetland ecologist at Louisiana State University and lead author of this recent study, first noticed the difference in red-imported fire ants after flooding during the aftermath of Hurricane Katrina. Red-imported fire ant populations seemed to boom in New Orleans after Katrina, and Hooper-Bui began to notice that people that had walked through the flood waters had huge unexplained rashes that turned out to be many, more severe fire ant bites.

Hooper-Bui discovered that both fresh and saltwater flooding increases the already aggressive nature of red-imported fire ants and upgrades their arsenal by giving them a larger head so their bite is stronger and much bigger venom sacs that make those bites more painful and increase the swelling. However, while freshwater flooding that occurs inland causes an increase of 34 percent in the volume of venom sacs, coastal saltwater flooding causes a whopping 72 percent increase. Coastal flooding also causes the red-imported fire ant colonies to breed larger and more aggressive ants than colonies located inland. Fire ants are able to cling together to build floating rafts made up of entire colonies in order to survive flooding, but this also forces them to subsequently locate and build a new nest. Hooper-Bui concluded that since frequent flooding disrupts colony life and makes it harder to find food, it is the stress caused by the increased flooding in the state, and particularly by the coast, that is forcing red-imported fire ants to adapt and breed larger, more aggressive ants that can better handle the harsher environment.

Unfortunately, things are only going to get worse in the coming years, with the Gulf of Mexico expected to raise sea levels along the state’s coastline by 4 to 7 feet by the end of this century, increasing tidal and storm-related flooding. The risk of flooding from rivers and rain is also steadily increasing throughout the state. Basically, if you live by the coast, you want to stay as far away from those red-imported fire ants as you possibly can.

Have you noticed red-imported fire ants being larger and more aggressive than in the past?