A population study of feral goats (Capra hirus L.), from Macauley Island, New Zealand

In August 1966, the entire population of hitherto undisturbed feral goats on Macauley Island, Kermadec Group, New Zealand, was destroyed. Of 3,200 animals (4/ acre) 1,047 were examined after death. Primary coat colours were black (37.8%), tan (11.9%) and white (0.7%). Horns were mostly of the twisted 'prisca' type, maximum lengths being 20.3 in. for males and 9.5 in. for females. Of 118 mandibles 8% showed a range of abnormalities including localised excessive wear, diseased alveolar bone and loss of teeth. Life expectancy at birth was 4.5 years.
22% of females over two years old were simultaneously pregnant and lactating and twins occurred in 39% of pregnancies. Corresponding figures in females under two years old were 1.4% and 2.0% respectively. Mortality of kids between birth and six months was estimated to be between 34% and 57%. A minimum estimate of pre-natal mortality was 33%. Some females bred twice yearly in two ill-defined seasons with peaks probably in August and March.
In the absence of predation, hunting or emigration the population appeared to be regulated by suppression of first year breeding, pre-natal mortality and high mortality of kids up to six months old.