Ant and Death

Ants have a sense of their own mortality

Worker ants accurately gauge their life expectancy, regardless of their actual age, and take on riskier tasks as they feel their days ebbing away. In social insects such as ants, bees and wasps, workers change tasks depending on their age. Older workers do the relatively risky foraging outside the nest, while younger ones engage in safer maintenance tasks within it. By extending the workers' average life span, this fine-tuning helps to maximise the fitness of the colony. However, no one knew whether the division of labour in ants was activated by age-related physiological changes or through some other mechanism.

The rest of the article is behind a subscription wall but I read the piece in the magazine the other day and the conclusions are fascinating. Half the ants in a colony had their life expectancy shortened either by CO2 exposure or by direct injury to their surface leaving them prone to infection. All the CO2 damaged ants started foraging away from the colony earlier and more often with the ones which had the most serious CO2 damage starting soonest. The physically injured ants followed the same pattern except that the more seriously injured started no sooner than the less serious ones.

It would seem that both the CO2 damaged and the physically damaged ants 'knew' their life span had been shortened and behaved in the same way as uninjured but aging ants do, that is, taking on more risky activity. The reason the most seriously physically harmed ants did not behave differently from less seriously harmed ones seems to be about the difficulty in gauging early death through infection as opposed to nervous system damage via CO2 exposure.

Amazing stuff.