Heroic ants sacrifice their lives to safeguard nest

September 30th, 2008 - 1:47 pm ICT by ANI  

London, Sept 30 (ANI): While studying social insect behaviour, researchers from the Agricultural University of Krakow, Poland, discovered a remarkable example of self-sacrifice in a species of ant found in Brazil.
They found that the ants sacrifice themselves in order to pre-empt a threat.
When the sunsets, the ants seal up the entrance to their nest, but in doing so a few remain outside to kick sand over the entrance hole until it becomes invisible. These ants then die due to the cold, or get blown away in the wind.
This door-sealing activity of these 2-millimetre ants (Forelius pusillus) represents the first recorded case of insects sacrificing themselves through a premeditated and pre-emptive procedure.
“The ants sacrifice their lives every evening even if the colony isn”t under attack by predators,” New Scientist quoted Adam Tofilski of the Agricultural University in Krakow, Poland, and head of an international team investigating the phenomenon, as saying.
The researchers discovered the nightly door-closing ritual after observing nest entrances of ants at field sites near Sao Simao in Sao Paulo state, Brazil. They observed how apparent stragglers were trapped outside every night.
“The nest entrance is sealed at sunset. One to eight workers finish the job from the outside and, in doing so, sacrifice their lives,” said Tofilski.
The task takes about 50 minutes and the technique the ants use to kick sand backwards over the hole with their hind legs is unique to the chore, reinforcing the evidence that this is a pre-meditated activity. Once their task is complete, they usually quickly walk away.
In order to trace the fate of these ants, the researchers placed sheets of thin plywood containing false openings over some real nest entrances.
These were used to transfer ants engaged in the task of sealing the holes to containers with sand at the base. The ants carried on working until they had finished and were then left to await the dangers of the Brazilian night.
The researchers found that out of 23 ants transferred in this way, only six survived until morning. The bodies of 10 were recovered, and the other seven were missing, most likely blown away and presumed dead.
The authors said that given the typical nest populations of 100,000, the sacrifice of up to eight workers a night is worth paying for the security of the nest.
Tofilski said that the ants are probably older workers approaching death who are more dispensable than their younger nest mates, and so are programmed to perform riskier tasks as they age.
The study is published in the American Naturalist. (ANI)

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