A writhing ball of slimed-up, musky-smelling snake might be just the level of grossness needed to repel the attacks of voracious fire ants.
New research published this spring in The Science of Nature revealed that the scent glands near the back-end of serpents can release enough nasty chemicals to kill ants on touch.
“It’s a remarkable event,” said Robert Vander Meer, a research chemist with the Agricultural Research Service of the U.S. Department of Agriculture.
Previous research had shown that Texas blindsnakes, a largely underground species, might repel ants using the secretions they produce from glands near their cloaca, or the opening from which all snakes defecate. Many snakes will secrete this musk from these glands, located on their undersides, near their tails, rubbing their whole bodies in it.
Dr. Vander Meer and his colleague, Paul Weldon, who was with the Smithsonian Conservation Biology Institute before his death in 2022, wanted to test these observations in the lab.
Dr. Weldon acquired scent-gland secretion samples from several species: the Middle American burrowing python, boa constrictor, ball python, king cobra, timber rattlesnake and unicolor cribo. First they sprayed musk taken from the Middle American burrowing python on ant species, but it didn’t seem to have much effect.
They then took the secretions from the other snakes and placed the substances in water offered to captive red imported fire ants and carpenter ants. Most ants avoided the secretion-laden liquid altogether, though carpenter ants seemed a little more resistant to the chemicals.
But some less prudent fire ants that touched the liquid containing snake-butt stank often died — they would curl up into a comatose state and never recover, Dr. Vander Meer said.
“Having spent weeks surrounded by gland secretions, that doesn’t surprise me,” said Tracy Langkilde, a biologist at Pennsylvania State University who wasn’t involved in the study. She lamented about horrible lunch breaks in her own work, which has involved “eating sandwiches after handling shweezy garter snakes.” The recent study’s observation that snake musk repels ants “makes a lot of sense,” she said, especially for burrowing snakes like those in the study that might come into contact with ants more often.
Dr. Langkilde usually studies physical adaptations for ant defense, such as lizards shaking them off. But this potential chemical defense “opens up a whole new area of ant research,” she said.
Dr. Vander Meer said the fact that so many snake species have secretions that repel ants may mean the feature is an evolutionary adaptation that developed early in serpents. The Texas blindsnake, for instance, is from an ancient lineage of serpents. Its glandular emissions most likely continued to improve as it repeatedly encountered ants. “The ancient history of the snakes and ants correspond with each other,” he said.
This is helpful for North American snakes as they contend with invasive imported red fire ants, which have an insatiable appetite for reptiles, especially eggs and younger snakes. “The snakes have an internalized defensive mechanism built in for potential ant predators,” Dr. Vander Meer said.
If so, it’s possible that mothers even secrete this scent on eggs after laying them as protection. Those species that act a little more motherly, staying with their eggs after hatching, might coat their young with the scents to protect them as well, Dr. Vander Meer speculated.
Meredith Swartwout, a postdoctoral ecologist at the University of Toronto-Mississauga who was not involved in the paper but who has studied fire ants, thinks the evidence of scent glands protecting snakes from predatory ants “seems dubious.” Some unpublished trials she ran on hatchlings didn’t reveal them secreting musk. “Perhaps only snake species that spend a lot of time living with or hunting ants are able to successfully use their scent gland secretions to deter ants,” she said.
For Dr. Vander Meer, the work is just starting. Since snake musk seems to repel — or even kill — fire ants, it may have potential for development as red imported fire ant control. He still has in a freezer the musk extracts that Dr. Weldon collected, and he plans to work on identifying and isolating the specific compounds that are effective against fire ants.
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