Yellow crazy ants are rather cute, as ants go. They don’t have pinchers, their bodies are delicate and golden colored and their little black eyes look friendly on almond-shaped heads.

But they are actually one of the most fearsome invasive species on the planet and are notoriously aggressive towards other species. Now baby seabirds in Hawai’i are falling victim to the ants' march—in a devastating manner, as Jason Bittel reports for On Earth.

The wedge-tailed shearwater nests in burrows on Pacific islands, hiding its young underground. This was a good strategy. But then the ants arrived. Researchers aren’t sure from whence they came; it may have been West Africa originally. But they do know that the invaders can arrive on driftwood rafts or as stowaways on ships. And they know this: The crazy ants' main weapon is acid, which they spray over any unwanted competitors, including the shearwater chicks.

“The chicks are adapted to stay in that burrow for safety and shelter, so they’ll sit there and just be swarmed by ants,” Plentovich told On Earth. “The parents continue to feed them, so we see chicks with big fat bellies, but as they grow, the chicks develop these horrible abnormalities.” Those wounds include missing toes, mangled beaks and even damage so severe that "their nostrils grow closed and skin covers the eyelid entirely," writes Bittel.

The horrific effects are just a hint of the full extent of invasive ants’ damage to ecosystems. If the shearwaters can’t survive, then the guano they usually leave on islands disappears… and the whole nutrient web is thrown off. The solution may be to fight fire with fire. Bittel writes:

On two islets, Mokuauia and Moku Nui, Plentovich oversaw the eradication of another invasive, bigheaded ants, only to see the area soon after overrun by yellow crazies. “The best control for an invasive ant is another invasive ant,” says Plentovich. “There’s still a lot about these ants we don’t understand.”

The spread of invasive ant species means that ant wars are breaking out around the world. Tawny crazy ants are pushing fire ants out in the U.S. (Both are invasive species.) The Asian needle ant is overwhelming the aggressive Argentine ant in some places. Poison can also drive ant species back. Much of the alarm over these invasions has to do with the fact that humans don’t notice the change until it appears it is too late for one species or another. Ants, after all, are very small.