Intersexual social behavior of urban white-tailed deer and its evolutionary implications

Abstract

White-tailed deer ( Odocoileus virginianus (Zimmermann, 1780)) are now common in many urban environments throughout their geographic range. Yet, how male and female deer in the urban environment associate, behave socially, and the evolutionary implications of that behavior remains unstudied. We examined predictions of the predation risk and the social factor hypotheses to explain intersexual grouping patterns and social behavior observed in white-tailed deer inhabiting the small city of San Marcos (population size ~45 000) in central Texas. Two routes were surveyed weekly from a vehicle at dawn and dusk for 1 year. Group size, composition, distance to vehicle, and alarm state of deer to the vehicle were recorded. Focal animal sampling was used to measure the time males and females spent and number of aggressions within one body length of each other when in groups. Female-only groups were most prevalent year round followed by mixed-sex groups, which increased in prevalence in summer and during the mating season. Alarm state was weakly related to group size but not to group composition. Males were farther apart and more aggressive than females in groups. Proportion of males in mixed-sex groups declined with increased group size. Intersexual patterns of grouping and social behavior of urban deer supported the social factor hypothesis but not the predation risk hypothesis.