Social incompatibility, alarm state, and sexual segregation in urban white-tailed deer

Abstract

Sexual segregation is prevalent among sexually dimorphic ruminants outside the mating season and no consensus has yet been reached to explain this phenomenon. Differential reactions to predation risk or sexual differences in aggression may be responsible for sexual segregation. I investigated how male and female white-tailed deer (Odocoileus virginianus) segregated in an urban environment. Two routes in San Marcos, Texas were surveyed from a vehicle at dawn and dusk for one year. Segregation was examined at the group level, at two spatial scales (groups within 300 or 600 m) and by amount of cover used (< 50 %, or > 50 %). Alarm response to the vehicle was measured for each group. Focal animal sampling was used to measure the time males and females spent within one body length of each other and the number of aggressions within one body length. Males and females were segregated in winter and spring but segregation declined throughout the summer, a trend previously unrecorded. Spatial segregation followed a similar trend. Akaike information criterion model selection indicated that alarm response was related to group size and group composition. Larger groups were less alarmed and female groups were less alarmed when controlled for group size. Females generally used larger groups than males outside of parturition. Males were further apart and more aggressive than females. The difference in group sizes between the sexes indicated that males and females used different avoidance strategies, preventing aggregation of the sexes. This is likely due to the more aggressive nature of males. Predation risk and social incompatibility may both contribute to sexual segregation.