Self-assessment strategy during contest decisions between male Great Himalayan leaf-nosed bats

Abstract

Agonistic interactions in animals are often settled based on the rules of an assessment strategy. We tested the predictions of evolutionary game theory models (including two models based on self-assessment: (a) the energetic war of attrition model, (b) the cumulative assessment model, and a third model (c) based on mutual assessment model) during contests between males of the Great Himalayan leaf-nosed bat Hipposideros armiger. We also studied the potential proxies of resource holding potential (RHP: body mass and forearm length) and their relationship to contest duration and the level of escalation. Overall, heavier males won more contests than lighter males, and they had an advantage in physical fights. In physical contests, the contest duration was positively correlated with the body mass of the loser but not the body mass of the winner. These results supported the prediction that males make decisions based on their own RHP (self-assessment: the energetic war of attrition model) rather than on RHP of their opponent (mutual assessment). Contest duration was not related to the forearm length of the winner or the loser. No relationship between body size (i.e., body mass and forearm length) and contest duration was observed for non-physical contests. This did not support any of the predictions applying to the energetic war of attrition model, the cumulative assessment model, and the mutual assessment model, indicating that no assessment occurred during non-physical contests. This study provides the first empirical evidence that bats make decisions based on their own RHP during agonistic interactions. This study provides empirical evidence supporting the hypothesis that during physical contests bats make decisions based on estimates of their own ability (self-assessment) rather than on a process of mutual assessment. This finding will facilitate comparative studies of fighting strategy across bat species.