Whistle Convergence among Allied Male Bottlenose Dolphins (Delphinidae, Tursiops sp.)

Dolphins are adept at learning new vocalizations "whistles# throughout life\ an ability thus far demonstrated in few nonhuman mammals[ In dolphins\ this ability is well documented in captivity but poorly studied in the wild\ and little is known of its role in natural social behavior[ This study documents the previously unknown phenomenon of whistle convergence among habituated free!living male bottlenose dolphins "Tursiops sp[#[ Over a 3 yr study period\ three male subjects formed an alliance\ spending most of their time together and cooperating to herd females[ Within individuals\ whistle repertoires were more variable than expected based on previous studies\ mostly performed with captive dolphins\ but became less so during the course of the study[ Among individuals\ the distinctiveness of individual repertoires decreased such that the three males were virtually indis! tinguishable by the end of the study[ Initially\ some whistle types were shared[ By the end of the study\ the three males had formed a close alliance\ and had all converged on one particular shared whistle form which they had rarely produced before forming the alliance[ The results are discussed in terms of their implications for the prevailing {signature whistle| hypothesis\ as well as possible mechanisms and functional signi_cance of whistle convergence among cooperating males[ Corresponding author] R[ Smolker\ Biology Department\ Marsh Life Sciences Building\ University of Vermont\ Burlington\VT 94394\ USA[ E!mail] rsmol! kerÝzoo[uvm[edu