Patients in hospital generally trust the nursing staff. After all, they have undergone training and, in some cases, have several years of professional experience.

In the case of carpenter ants, it is not nursing expertise that determines who cares for the patients: “There are no specialised ‘medics’ in the colonies. Instead, this task is carried out by worker ants that are in the process of transitioning from brood care to foraging,” says Dr Erik Frank, senior author of the study and head of an Emmy Noether research group at the Chair of Animal Ecology and Tropical Biology at the University of Würzburg. This transitional phase for the ants usually lasts 20 days.

Another crucial factor is how many previous interactions the carer has had with the injured ant, says Alba Motes-Rodrigo, co-author from the University of Lausanne (Switzerland). These include social interactions such as grooming one another or encountering each other by chance in the nest and touching each other with their antennae.

Ants transitioning between indoor and outdoor duties roam throughout the entire nest and are therefore better connected than other members of their colony. The research team published their findings in the journal *Proceedings of the National Academy of Sciences* (PNAS).

Fully automated tracking: 660 ants under scrutiny

For the study, the team examined six colonies, each comprising 110 ants of the species Camponotus fellah, which belongs to the genus of carpenter ants and is found primarily in the Middle East. Using a fully automated tracking system, the researchers were able to precisely monitor the movements and hundreds of thousands of interactions of each ant, as well as their wound care, over a period of weeks.

“We have long known that the spatial organisation of a colony governs everyday tasks such as brood care or foraging. But our findings go even further,” explains Dr Ebi George, a co-author from the University of Lausanne. They show that the everyday spatial and social overlap between workers also determines temporary tasks such as life-saving wound care, George elaborates.

Carpenter ants: Masters of amputation

In a previous study, Frank and his team had already observed how carpenter ants treat wounds: they amputate the injured legs of their fellow ants by biting them off and treating them with antimicrobial substances. Their guiding principle is always: better safe than sorry.

The ants carry out prophylactic amputations. This not only protects the colony from infection but also doubles the survival rate of the injured workers. “Back then, we were able to show how the wounds are treated. Our current study now reveals who is primarily responsible for this,” says Frank.