Title: The benefits of long-term field studies: Insights gained from tracking the social and communicative behavior of northern elephant seals (Mirounga angustirostris)
Abstract: Operating within one of the most polygynous breeding systems documented among mammals, adult male elephant seals battle for position within dominance hierarchies that determine access to large harems of females during the breeding season. Our research group at the University of California Santa Cruz has evaluated the vocal and social behavior of male northern elephant over the past decade by tracking the social, spatial, and communicative behavior of known individuals within and between breeding seasons. This long-term effort has demonstrated that males are operating within a dynamic, familiar, stable social network that is maintained through the exchange of ritualized vocal displays. While specialized signals emitted by competing males often convey honest information about fighting ability in other species, we have demonstrated that social knowledge gained through prior experience with signalers maintains structured dominance relationship among breeding males. Using sound analysis and playback experiments with both natural and modified vocalizations, we have shown that males do not rely on encoded information about phenotype, but rather recognize individual acoustic signatures produced by rivals with whom they have previously interacted through associative learning. Further, we have shown that a male’s response to a competitors’ call is modulated by relative position in the hierarchy, and individuals react differentially to familiar challengers based on the outcome of previous interactions. To evaluate the ontogeny of these specialized signals, we tracked hundreds of male seals of different developmental stages throughout development, and found that the progressive stabilization of these individual vocal signatures coincides with the establishment of familiar dominance relationships between competitors. These findings demonstrate that social knowledge of rivals alone can regulate dominance relationships among males within large, spatially dynamic social groups, and contributes broadly to comparative studies of agonistic signaling among animals competing for resources.