A population study of feral goats (Capra hirus L.), from Macauley Island, New Zealand
- N.Z. Wildlife Service, Dept. of Internal Affairs, Wellington
- Animal Ecology Division, D.S.I.R., Lower Hutt
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.