May 7, 2009

Study IDs how ants know a nestmate is dead

U.S. entomologists say they have discovered how ants know when a nestmate has died and its time to remove the body from the colony.

University of California-Riverside scientists say when an ant dies its body is quickly picked up by living ants and removed, thus limiting the risk of colony infection by pathogens from the corpse.

Up to now most entomologists theorized dead ants release chemicals created by decomposition, thereby signaling their death.

But in the new study, scientists working on Argentine ants provide evidence for a different mechanism.

The researchers said all ants, both living and dead, continually emit death chemicals, but live ants have them along with other chemicals associated with life. When an ant dies, its life chemicals dissipate or are degraded, and only the death chemicals remain.

It's because the dead ant no longer smells like a living ant that it gets carried to the graveyard, not because its body releases new, unique chemicals after death, said Dong-Hwan Choe, lead author of the research.

Choe said the findings resolve a conundrum of long-standing in animal behavior and correct a misinterpretation of previous results that has become both popular and widespread in literature.

The study that included Professors Michael Rust and Jocelyn Millar appears in the early online edition of the Proceedings of the National Academy of Sciences.