Rescue behavior in non-human animals: a systematic review from a comparative perspective

Abstract

Rescue behavior is an extreme form of altruism in which the rescuer positions itself in immediate danger to help a victim at risk of death or severe harm, assuming a high cost to its own well-being. From this action, the rescuer does not receive an apparent reward. Helping behaviors and animal cooperation are widely observed phenomena in various species. However, rescue behavior is extremely rare in nature due to its cost-benefit relationship. Additionally, given the lack of a formal conceptual definition for this phenomenon that differentiates it from other forms of cooperation or altruistic behaviors, there are not many controlled experimental works exploring it. In this study, it was conducted a systematic review of existing literature that experimentally explores rescue behavior in non-human animals. The found articles are analyzed in categories and records to integrate the evidence, exploring different definitions for the behavior, the experimental methods used, and the characteristics presented in the various groups of animals studied. A discussion is generated around the results, focusing on highlighting generalizable conclusions and the main differences among articles. Questions and limitations regarding the methodological and conceptual approach to rescue behavior in relation to theories of altruism, cooperation, kin selection, and observational evidence are proposed. This is the first study that systematically compiles every existing empirical literature on the rescue phenomenon across all taxa.