Proposed Scheme for Comparative Analyses of Alliance Formation in the Genus Tursiops : A Systematic Review

ABSTRACT

Male alliances to cooperate for access to females have been reported in some populations of the genus Tursiops , with variation in their status (allied or not). Given the variation in alliances, it may be possible to identify the factors that favor alliance formation through a cross‐population comparative analysis. However, the association criteria that determine alliance status in these previous studies are inconsistent, which has prevented researchers from determining whether the variation in alliances reflects the inherent characteristics of each population or is simply pseudo‐variation caused by criteria differences. To ensure the validity of future comparative analyses, through a literature review, we investigated the extent to which inconsistencies in association criteria among studies affect the variation. In 55 studies across 23 regions, we found discrepancies between the alliance status reported in the original studies and the outcomes of analyses in which criteria were exchanged within each study. Our results suggest that while inconsistencies in association criteria currently have little influence, the possibility that inconsistencies account for pseudo‐variations in the alliance status cannot be excluded. Based on this, we recommend that alliances should be determined by criteria that integrate behavioral data in addition to association data.