Sex differences in weather sensitivity can cause habitat segregation: red deer as an example

Sex differences in habitat use (habitat segregation) are widespread in sexu ally dimorphic ungulates. A possible cause is that males are more sensitive to weather than females, leading to sex differences in sheltering behaviou r (the 'weather sensitivity hypothesis'). However, this hypothesis has neve r been tested. We considered the allometric rates of net energy gain during times of cold weather,and food shortage in a model. We argue that the high er absolute heat losses relative to intake rates of larger ungulates should indeed lead to higher weather sensitivity in males than in females. Furthe rmore, we tested the weather sensitivity hypothesis empirically in red deer , Cervus elaphus, on the Isle of Rum, U.K. We predicted that (1) use of rel atively exposed, high-quality forage habitat should be negatively influence d by bad weather; and (2) this influence should be stronger in males. We fo und that bad weather (strong wind, low temperature, heavy rain) in winter a nd spring influenced use of high-quality forage habitat negatively in all d eer; that adult males responded more strongly to low temperature and strong wind than did females; and that adult males foraged on windy days at bette r sheltered sites than did females. Thus, the weather sensitivity hypothesi s is supported both theoretically and empirically. We suggest that the weat her sensitivity hypothesis ran potentially explain winter habitat segregati on in a large number of ungulate species. (C) 2000 The Association for the Study of Animal Behaviour.