`Slave ants rebel against enslavers`

Ants enslaved by other ant species damage their oppressors through repeated acts of sabotage, says a new study.

Updated: Sep 27, 2012, 14:26 PM IST

Berlin: Ants enslaved by other ant species damage their oppressors through repeated acts of sabotage, says a new study.

The "slave rebellion" was first observed in 2009 by Susanne Foitzik, professor at Johannes Gutenberg University Mainz, Germany. The latest findings, however, show this behaviour is widespread and not an isolated instance.

In fact, in three different enslaved populations in West Virginia, New York and Ohio in the US, involving T. longispinosus species, workers have been observed to neglect and kill the offspring of their P. americanus slave masters rather than care for them.

As a result, an average of only 45 percent of the offspring survived. This presumably reduces the strength of the parasite ants in the area and thereby increases the chances of survival for the neighbouring colonies populated by the slave ants` kins.

More than half of all animal species live in parasitic relationships, exploiting their so-called hosts, according to a Johannes Gutenberg statement.

From the perspective of evolutionary history, the American slave-making ant P. americanus is an old social parasite that is entirely dependent on other ant species for its survival.

As Foitzik and her work group have shown, the enslaved worker ants feed and clean the larvae, thereby raising the offspring of their social parasite - but only up to a certain point.

These ants become slaves when workers from the slave-making ant colony attack the nests of the host species T. longispinosus, kill the adult ants, and steal the brood.

Back in the masters` nest, which can be located in hollow acorns, nutshells, or twigs, the brood care behaviour of the emerging slave workers is exploited to the advantage of the slavemaker species.

"Probably at first the slaves cannot tell that the larvae belong to another species," explains Foitzik. As a result, 95 percent of the brood survives the larval stage. But the situation changes as soon as the larvae pupate.

"The pupae, which already look like ants, bear chemical cues on their cuticles that can apparently be detected. We have been able to show that a high fraction of the slavemaker pupae are killed by slave workers."

The pupae are either neglected or actively killed by being attacked and torn apart. Several slaves at once may assault a pupa, which is unable to move or defend itself during the pupal stage and is also not protected by a cocoon.