Tests of hypotheses for spatial segregation in carnivores: Habitat segregation or social avoidance

Sexual segregation occurs within a species when sexes differ in habitat requirements or when differences in behavior cause individuals to avoid the opposite sex. Studies of sexual segregation in carnivores suggest segregation between reproductive classes is present and driven by habitat and social factors. Habitat segregation is usually benign but social segregation can have negative impacts. In northeastern Washington, heavy hunting of male mountain lions (Puma concolor) resulted in a net immigration of younger males. As resident males were harvested; younger immigrant males occupied their territories. Such changes in the sex and age distribution can increase the likelihood of infanticide and females with offspring may respond by using space differently than males. In central Washington, light hunting of males resulted in a net emigration of younger males and a stable sex and age distribution including older resident males. I calculated utilization distribution overlap indexes (UDOI) and compared male overlap of independent females to male overlap of females with kittens to test whether habitat or social segregation was related to sexually dimorphic spatial use in the two populations. Analysis of variance revealed that avoidance of males by females with kittens increased during summer, when kittens were vulnerable, in both the heavily hunted and lightly hunted areas. Females with kittens in both study areas decreased their overlap with males to about 1/3 of the overlap they had as independent females---however avoidance of males was more pronounced in the heavily hunted population. In addition, I compared the use and availability of elevation within each individual's home range to test whether females with offspring used elevation within their home ranges differently than solitary females or males. Analysis of variance between use and availability of elevation revealed that in the heavily hunted area, females with offspring used higher elevations than were available within their home ranges and independent females and males did not. In the lightly hunted area, no differences in use/availability were detected between reproductive classes. These results support the social avoidance hypothesis of sexual segregation. Heavy hunting of males appears to increase sexual segregation in mountain lions and other potentially infanticidal carnivores.