Female-Biased Mortality in a Sexually Dimorphic Ungulate: Feral Cattle of Amsterdam Island

I investigated the scale and pattern of mortality among feral cattle (Bos taurus) occurring on Amsterdam Island in 1988 to test hypotheses related to sexual dimorphism. Because cattle are sexually dimorphic ungulates and all deaths apparently were due to starvation, mortality was expected to be biased towards males. Mortality of juvenile males was higher than that of juvenile females (22.4 versus 11.7%), but mortality of adult males was lower than that of females (18.3 versus 47.7%). Causes for differential survival in adult age-classes are uncertain, but could involve sex differences in use of habitat, or consequences of previous selection during domestication.