Rescue behaviour and sanitary care in the ants

Abstract

Prosocial behaviour - actions that benefit others - belongs to the most important elements of the social way of life. Rescue behaviour - coming at the rescue of endangered individual(s) - belongs to the most interesting subcategories of risky prosocial behaviour. Rescue behaviour was first described in the animal world in the army ants from the species Eciton hamatum, and was subsequently studied in ants from many other species from the subfamilies Formicinae, Myrmecinae, Ponerinae and Dolichoderinae. That research was carried out both in the field and in the laboratory with the use of a wide spectre of behavioural tests involving confrontations of potential rescuers with individuals characterized by impaired mobility (immobilized as a consequence of being buried in sand or/and trapped in artificial snares), or with ants attacked by their natural enemies, such as antlion larvae, spiders or termites. The aim of that research was to analyse the effects of numerous factors exerting influence on the propensity of the ants to engage in rescue behaviour and on behavioural patterns expressed in that context, including, in particular, the so-called precise rescue behaviour, a testimony of unexpectedly advanced cognitive skills of these insects. These factors included age, behavioural specialization and life expectancy of both victims and potential rescuers, as well as their previous experiences, genetic factors, and ant species and specificity of its ecology. Some studies also checked if the ants rescue not only their nestmates but also individuals from alien colonies of the same species or from alien species, or involved attempts at identification of signals emited by the victims as the so-called calls for help. Some researchers also reported that some ants provide sanitary care to their nestmaes injured by natural enemies or suffering from infections and found out that such care may bring benefits to both victims and their healthy nestmates, as the rescued individuals may continue to work for their colony, and contacts with infected individuals may exert a stimulatory influence on immune system of healthy workers and thus become an element of prevention of the spread of infectious diseases. Nevertheless, reduced life expectancy is often accompanied in ants by the so-called social withdrawal that may also be expressed as reduced propensity to engage in rescue behaviour. Such individuals are also less readily rescued by their nestmates. Rescue behaviour was observed and analysed also in vertebrates, birds (two species) and numerous mammals (rats, mice, dogs, mongoose, boars, elephants and various cetaceans and primates). The research on animal rescue behaviour throws an important light on the evolution of altruism and prosocial behaviour as well as on cognitive skills of animals and factors that may enhance or reduce them,  The results of the research on ant rescue behaviour also provide an excellent illustration how comparative research may contribute to the formulation of general rules and principles by allowing us to gain a more complete picture of the studied issues and to draw more general conclusions.