Red imported fire ants (Solenopsis invicta) are nasty little critters. You’ll know what I’m talking about if you’ve ever accidentally stood on one of their mounds, because it doesn’t take long for the aggressive insects to swarm up your legs and start striking you en masse, leaving you peppered with painful and irritating stings. Alongside racking up billions of dollars each year in medical bills, these ants are also major agricultural pests in some areas, costing farmers millions in crop losses and vet bills.
Now, proving once again that they are formidable invaders not to be messed with, scientists have found that the creepy crawlies are causing a significant reduction in the nest success of caimans in Argentina. Not only do the insects gobble up the baby crocodilians as they hatch, but they also drive the mother away so she can’t look after any survivors. These findings have been published in the Journal of Herpetology.
Although native to central South America, the red imported fire ant (RIFA) is an invasive species that has established itself in numerous other spots in the world, becoming a significant pest in the U.S. and other countries. It’s also becoming increasingly recognized as a formidable predator of various reptile species, triggering changes in their populations in the wild. One study, for example, found that they can kill more than 70% of sea turtle hatchlings in Florida, but as New Scientist points out, they are also known for having a taste for snakes, lizards and even baby deer.
Recently, scientists observed that RIFAs were also invading caiman nests in Argentina during the breeding season, exploiting the warm and moist bedding material for their eggs and larvae, so they decided to investigate whether their presence was affecting nest success. In the lab, the ants were found to decrease hatchling survival rates by around 10% when compared with uninvaded nests. In the wild, however, they wreaked significantly more havoc on nests, causing a 43% reduction in nest success.
This decline was found to be due to a combination of both direct and indirect effects, whereby the ants both attack the mother—forcing her to abandon the nest and thus preventing her from caring for her babies—and also sting and eat the babies as they hatch. According to the study, the ants can kill around a quarter of broad-snouted caiman hatchlings during breeding season.
While this may sound like a lot, it doesn’t have conservationists worried yet and should not represent a substantial threat to caiman populations in South America given the fact that both these species evolved together here. Furthermore, as New Scientist points out, RIFAs have predators of their own, like the decapitating fly, which help control their numbers.