Crazy ants are currently invading Texas and the southeastern United States, displacing and eliminating the fire ants throughout those areas, according to new research from The University of Texas at Austin. This is of course not a surprise for many of those throughout those regions who have had experiences with those ants. This is just the most recent of the recurrent ant invasions that have been happening since large-scale human movement between North and South America began in the 1800s. These invasions have had profound effects on the natural environments and ecosystems of North America.
The new research has found that the “ecologically dominant” crazy ants are diminishing the biological diversity of the areas that they invade — eliminating a variety of different ant and arthropod species. The researchers argue that their spread can be limited if proper measures are taken — mostly if people take care to avoid transporting them inadvertently.
“When you talk to folks who live in the invaded areas, they tell you they want their fire ants back,” said Ed LeBrun, research associate with the Texas invasive species research program at the Brackenridge Field Laboratory in the College of Natural Sciences. “Fire ants are in many ways very polite. They live in your yard. They form mounds and stay there, and they only interact with you if you step on their mound.”
The crazy ants though, they go everywhere — regularly invading people’s homes, nesting in them, in their walls, and damaging electrical equipment — all in great numbers.
Crazy ants were first found in the US back in 2002 “by a pest control operator in a suburb of Houston, and have since established populations in 21 counties in Texas, 20 counties in Florida, and a few sites in southern Mississippi and southern Louisiana. In 2012 the species was formally identified as Nylanderia fulva, which is native to northern Argentina and southern Brazil. Frequently referred to as Rasberry crazy ants, these ants recently have been given the official common name ‘Tawny crazy ants’.”
As mentioned before though, ant invasions are nothing new — the Argentine ant came through the port of New Orleans sometime 1891, before spreading throughout the South. “In 1918 the black imported fire ant showed up in Mobile, Ala. Then in the 1930s, the red imported fire ant arrived in the U.S. and began displacing the black fire ant and the Argentine ants.”
The press release continues:
The UT researchers studied two crazy ant invasion sites on the Texas Gulf Coast and found that in those areas where the Tawny crazy ant population is densest, fire ants were eliminated. Even in regions where the crazy ant population is less dense, fire ant populations were drastically reduced. Other ant species, particularly native species, were also eliminated or diminished.
LeBrun said crazy ants are much harder to control than fire ants. They don’t consume most of the poison baits that kill fire ant mounds, and they don’t have the same kinds of colony boundaries that fire ants do. That means that even if they’re killed in a certain area, the supercolony survives and can swarm back over the area.
“They don’t sting like fire ants do, but aside from that they are much bigger pests,” he said. “There are videos on YouTube of people sweeping out dustpans full of these ants from their bathroom. You have to call pest control operators every three or four months just to keep the infestation under control. It’s very expensive.”
The researchers speculate that in the ants native area — northern Argentina and southern Brazil — that populations are probably held in check by other ant species/enemies. In the US there doesn’t appear to be any such natural controls though.
As a result, the crazy ants here “can attain densities up to 100 times as great as all other ants in the area combined. In the process, they monopolize food sources and starve out other species. The crazy ants, which are omnivorous, may also directly attack and kill other ant and arthropod species. The overall result is a significant reduction in abundance and biodiversity at the base of the food chain, which is likely to have implications for the ecosystem as a whole.”
“Perhaps the biggest deal is the displacement of the fire ant, which is the 300 pound gorilla in Texas ecosystems these days,” said LeBrun. “The whole system has changed around fire ants. Things that can’t tolerate fire ants are gone. Many that can have flourished. New things have come in. Now we are going to go through and whack the fire ants and put something in its place that has a very different biology. There are going to be a lot of changes that come from that.”
There remains much that is unknown about the Tawny crazy ants, including their potential range, so it is unclear what effects they may potentially have. As of now, “most of the colonies are in fairly wet environments with mild winters, near the coast, so it may be the case that they can’t thrive in drier or colder climates, and that fire ants will remain dominant in those areas.”
Their spread is also limited by the fact that because the reproductive members of their species don’t fly, they can’t spread very quickly. “When left to their own devices, crazy ant colonies can only advance about 200 meters a year. That means they’re dependent on humans to colonize new areas.”
“They are opportunistic nesters,” said LeBrun. “They can take up residence in everything from a house plant, to an empty container left outside, to an RV. So they’re easily transported by us. But the flip side of that is that if people living in or visiting invaded areas are careful and check for the crazy ants when moving or going on longer trips, they could have a huge impact on the spread.”
The researchers state that nursery products are also likely one of the key ways that the crazy ants spread, “so both buyers and sellers should be watchful for these ants. Cutting down on the number of transplantation events could slow the spread by years or decades. And that extra time could give the ecosystem time to adapt and researchers time to develop better control methods.”
“We can really make a difference,” he said, “but we need to be careful, and we need to know more.”
The new research was recently published in the journal Biological Invasions.