A comparative analysis of precision rescue behaviour in sand-dwelling ants

Abstract

A sand-dwelling Mediterranean ant, Cataglyphis cursor, recently was discovered to engage in two new forms of rescue behaviour, behavioural patterns that require would-be rescuers to recognize what, exactly, holds nestmates in place. That is, when sand digging and limb pulling, two well-known forms of rescue in ants, did not result in release of victims ensnared with nylon thread and partially buried beneath the sand, rescuers next began to transport sand away from the snare and to direct their behaviour to the snare in particular, biting and tugging at the snare itself. To determine whether these new forms of precisely directed rescue behaviour, as well as their exclusive delivery to nestmates, as in C. cursor, were characteristic of other ants occupying similar ecological niches, we conducted experiments with five sand-dwelling Mediterranean ant species: Cataglyphis floricola, Lasius grandis, Aphaenogaster senilis, Messor barbarus and Messor marocanus. Our experiments revealed the full range of rescue behaviour, including snare biting and sand transport, in two species, C. floricola and L. grandis. Both species directed rescue exclusively towards nestmates, treating other individuals, even conspecifics, with aggression, thus highlighting the ants' discriminative capacities. Differences in the performance of rescue behaviour between these and the remaining species mirror differences in their ecology, including the threat of predatory antlions. Finally, because this precisely directed and exclusively delivered rescue behaviour in ants resembles behaviour that has been labelled empathy in rats, our results demonstrate that what can appear to be complex, cognitively motivated behaviour might come about through much simpler mechanisms.