Among the invasive creatures that have been introduced in the South one of the most deadly is a species of red ant. The fire ant is the largest single cause of death for fawns in Florida. Fawns are taught to freeze and remain in place if their mother isn't around, and if they freeze near a fire ant mound the bites of the aggressive ants kill them.
It isn't just fawns or feral kittens that the ants kill, this CBS article
reports of the million+ dollar settlement paid by a nursing home to the family of a patient killed by ant bites.
The bite is highly acidic and is treated by a baking soda and water paste, but, by the time you realize there's a problem, you will be treating a dozen bites.
The pesticides that are most effective against fire ants kill almost everything else, and a water table within a couple of yards of the surface would mean polluting your well if you used them.