Toward a behavioral ecology of rescue behavior

Abstract

Although the study of helping behavior has revolutionized the field of behavioral ecology, scientific examination of rescue behavior remains extremely rare, except perhaps in ants, having been described as early as 1874. Nonetheless, recent work in our laboratories has revealed several new patterns of rescue behavior that appear to be much more complex than previously studied forms. This precisely-directed rescue behavior bears a remarkable resemblance to what has been labeled empathy in rats, and thus raises numerous philosophical and theoretical questions: How should rescue behavior (or empathy) be defined? What distinguishes rescue from other forms of altruism? In what ways is rescue behavior in ants different from, and similar to, rescue in other non-human animals? What selection pressures dictate its appearance? In this paper, we review our own experimental studies of rescue in both laboratory and field, which, taken together, begin to reveal some of the behavioral ecological conditions that likely have given rise to rescue behavior in ants. Against this background, we also address important theoretical questions involving rescue, including those outlined above. In this way, we hope not only to encourage further experimental analysis of rescue behavior, but also to highlight important similarities and differences in very distant taxa.

Figure 1.

A larval pit-digging antlion (Myrmeleon sp.) exposed on the sand surface (top left), and in the process of burying itself under the sand (top right). Bottom: Funnel-shaped antlion pits in fine sand

Figure 2.

Mean duration of four rescue behavior patterns performed by groups of 5 Cataglyphis cursor ants in response to an ensnared test stimulus

Figure 3.

In this photograph, a C. cursor rescuer already has transported sufficient sand away from the victim, exposing the nylon thread snare holding its nestmate in place (part of the white filter paper has been exposed as well), and is shown biting the nylon thread snare that holds the victim to the paper

Figure 4.

Mean duration of rescue behavior performed by C. cursor rescuers, either all foragers, all nurses, or all inactives, in the presence of a single experimentally ensnared victim, either a forager, a nurse or an inactive