Ants Use Sex and Bondage to Out-Compete Rival Species

A new field study of two rival ant species has shown that ant queens will willingly mate with males from the opposing group in order to quite literally serve as "sperm parasites," stealing potential female births. The result is an unusual bedroom arms race between these ants, where they develop new strategies to trick males or to escape a rival queen's lustful clutches.

The study, recently published in the journal Proceedings of the Royal Society B, details how two species of Pogonomyrmex harvester ants dwelling in deserts along Arizona and New Mexico's boarder have occasionally and aggressively hybridized.

According to the study, these ants suddenly find themselves locked in a bizarre display of competitive mating once a year directly following summer monsoon rains. During this time, males from rival colonies don't appear to be able to tell a difference between their own queen and rival queen, and will mate with whoever is willing.

However, the researchers observed that sometimes these males realize they've made a mistake in the middle of their... ahem... session, and will slow down while they struggle to break away. They do this in order to conserve sperm - limited seed that could still be used to make a healthy ant with their proper queen during the brief mating period.

Interestingly, these rival queens have developed a horrifying form of bondage to prevent these suddenly sobered males from getting away.

"They lock slow males in copula significantly longer," explained researcher Helms Cahan, "until they eventually deliver the same amount of sperm that they normally would have."

"Essentially, they are sperm parasites," she said in a statement.

So why do these queens even want to mate with a rival colony's males to begin with? The researchers found that this "stolen" sperm is reserved for a time when the queen is producing sterile hybrid females - ideal workers for the nest. Without males bumbling into the wrong nest and mating with the wrong queen each year, both opposing colonies would find themselves lacking a ready worker supply.

"In this harvester ant system there really needs to be some sort of stalemate," added study leader Michael Herrmann, "because if the males actually were able to tell what type of female they were mating with, they would cut off the sperm to the queens that need it."

The researchers add that this illustrates the power of female influence on the natural world, where "they have their own distinct evolutionary interests and are just as capable of imposing those interests on their partners when conditions warrant."