Agonistic Interactions and Tail-cocking Posture in the Black Vulture (Coragyps atratus)

Abstract

In animals, social behavior and group-living come with many benefits and costs that depend on the life history contexts of individual species. While living in groups can aid individuals in finding resources, for example, conflicts can arise over access to those resources that result in the formation of dominance hierarchies, along with unique methods of signaling and interacting. The black vulture (Coragyps atratus) is a species that exhibits complex group-living behaviors, forming communal roosts where individuals selectively associate with kin, display agonistic behavior towards unrelated rivals, and form dominance relationships based on factors like age and breeding status. The social interactions of black vultures have been described in a few studies, but questions on the circumstances around certain behaviors persist.

This study examined the tail-cocking posture of black vultures, as well as the conditions surrounding certain agonistic interactions such as chases and extended fights. An analysis of camera trap footage of vultures at a communal roost in Kempton, Pennsylvania was conducted; it found that there are a variety of behaviors associated with tail-cocking, and more information is needed to determine the contexts in which it occurs and if it incites responses from conspecifics, and that threatening signals were utilized more regularly before fights than in chases, but the initiation of a threat did not necessarily predict the nature of a dominance relationship between individuals.