Hierarchical dominance structure in reintroduced California condors: correlates, consequences, and dynamics
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Populations of reintroduced California condors (Gymnogyps californianus) develop complex social structures and dynamics to maintain stable group cohesion, and birds that do not successfully integrate into group hierarchies have highly impaired survivability. Consequently, improved understanding of condor socioecology is needed to inform conservation management strategies. We report on the dominance structure of free-ranging condors and identify the causes and consequences of rank in condor populations by matching social status with the behavioral and physical correlates of individual birds. We characterized the hierarchical social structure of wild condor populations as mildly linear, despotic, and dynamic. Condor social groups were not egalitarian and dominance hierarchies regulated competitive access to food resources. Absence of kin-based social groups also indicated that condor social structure is individualistic. Agonistic interactions among condors were strongly unidirectional, but the overall linearity and steepness of their hierarchies was low. Although one aggressive male maintained the highest dominance rank across the 3-year observation period, there was considerable fluidity in social status among condors within middle and lower rank orders. Older condors were more dominant than younger birds and younger males supplanted older females over time to achieve higher status. Dominance rank did not predict the amount of time that a bird spent feeding at a carcass or the frequency that a bird was interrupted while feeding. Thus, younger, less dominant birds are able to obtain sufficient nutrition in wild social populations.
KeywordsCalifornia condor Socioecology Dominance hierarchy Reintroduction
We wish to acknowledge and thank the following funding agencies, collaborators, staff, assistants, and partner organizations: United States Fish and Wildlife Service (USFWS), Instituto Nacional de Ecologia (INE), Comision Nacional Para El Conocimiento y Uso de la Biodiversidad (CONABIO), Secretaria de Medio Ambiente y Recursos Naturales (SEMARNAT), Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (CICESE), Wildcoast/Costasalvaje, The Los Angeles Zoo, Sempra Energy, Mohammed Saad, Jeff Zuba, Lisa Nordstrom, Kristin Duncan, Alan Lieberman, Katika Bade.
This research was approved by the San Diego Zoo IACUC animal welfare committee (Project ID#11-014) and the Instituto Nacional de Ecología, México.
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