New research published in this month's Animal Behaviour reveals that ants seem to be able to predict their own best before dates.
Dawid Moron from Jagiellonian University in Poland artifically aged European Myrmica scabrinodis ants by exposing them to CO2, which damages the nervous system, or by giving them small injuries to make them vulnerable to infection and dehydration. Over the following five weeks the team then followed up how the injured ants fared against their uninjured nest-mates, and what roles they fulfilled in their colonies. Intriguingly, compared with uninjured ants of a similar age, the compromised individuals tended to take on higher risk tasks, such as foraging outside the nest, at a much younger age than normal. And the more severe their injuries, the sooner they took on these tasks. Such roles are usually assigned only to much older ants, which are deemed more expendable because they are closer to the ends of their lives. They are also more likely to carry parasites and other infections that might pose a threat to the colony, so it makes sense for them to spend more time outside the nest, compared with more valuable younger healthier specimens, that are confined to barracks initially.
These new findings shed light on how this pecking order might be achieved, which is at least partly due to ants having a strong grasp of their own mortality, and even their "time to live"!