| Nubian ibex (Capra ibex nubiana) were studied to evaluate a nutritional hypothesis for sexual segregation. The hypothesis was based on the allometry of gut volume and metabolic requirements, and the heterogeneity of forages in different habitats. This study was hierarchical in design: lower level functions were proposed to drive higher level phenomena. Sex-related differences in digestive capacity were suggested to account for forage selection and eating behaviors of males and females. In turn, forage selection determined habitat choice. Social organization was perceived to result from differences in habitat selection by sex/age cohorts.;Full balance digestion trials demonstrated that males, lactating, and non-lactating females were equally capable of digesting dry matter and neutral detergent fiber of a grass and legume hay. However, retention times of Cr-mordanted fiber by males were longer than those of females, and lactating females retained fiber longer than non-lactating females. Lactating females fully compensated for their greater intake by increasing gut fill.;Males and females ruminated for nearly 10 hours per day when fed a wheat/rye hay, but because intakes differed, females chewed each unit of intake more both when eating and when ruminating. These data, coupled with measures of digestion and retention, suggested that mastication may be a pivotal process utilized by females to increase digestion rates relative to males.;Field observations collected over a 26 month period revealed that mature males were found in groups separate from females, except during rut. Immature males separated from female-dominated groups at approximately the age when their body mass surpassed that of females. Although there was broad overlap in areas used during the non-rut period, 89% of females were observed in quadrats where no mature males occurred. |
