Reproductive tolerance in male primates: Old paradigms and new evidence.

Within social groups of primates, males commonly compete over reproduction, but they may also rely on cooperation with other males. Theory suggests that it may be adaptive for male primates to tolerate some reproduction by other males if reproductive tolerance fosters cooperation, particularly that dominant males yield so-called reproductive concessions to subordinates to entice their cooperation. We review four recent studies that claimed to have found evidence for reproductive concessions or similar forms of reproductive tolerance. However, upon critical reevaluation of their results, no study provides conclusive support for reproductive concessions as predicted by theoretical models. Yet two studies demonstrated a form of reproductive tolerance that cannot be explained by any of the existing models, and that seems to have evolved only in multi-male, multi-female societies with diverse strategic options for males. Our article provides guidance how to study this form of reproductive tolerance in the absence of a unifying model.