Every night, several ants sacrifice themselves for the survival of the colony.  When most of the ants have retreated inside the nest at sunset, up to eight ants will stay outside to fill in the entrances with sand. Tofilski’s team found chances of survival were less than 25% for the stragglers, thereby making this nightly task suicidal.

Brazilian ants seal their nest from the outside every night. Photo: Tofilski et al., American Naturalist (November 2008)

Many questions arise as a result of this study.  For example, how is it determined which ants remain outside the nest?  Do the older, sicker ants sacrifice themselves for the greater good?  The researchers are also unsure who or what the Brazilian ants are protecting their nest from each night. Are they protecting the colony from army ants?

This fascinating study will be featured in the November issue of the journal American Naturalist.

For more information, see ScienceNOW Daily News: “Last Ant Standing” by Charles Choi