The feral goats of Raoul Island,and some effects of hunting on their body size and population density

Abstract

A campaign to eradicate goats (Capra hircus L.) was begun in August–October 1972 on Raoul Island, Kermadec group, 1000 km north-east of New Zealand. Of a total of 1286 animals killed, 155 were examined and dissected. The coat colour of 88% was pradominandy black, and of these 80% were patterned with white and/or brown. The hair was short in 85% of the goats, but a few males were shaggy all over. No throat tassels or other features of improved breeds were seen. Both sexes were fecund by 1 year of age. Conceptions occurred up to the winter solstice, but none was recorded for at least 4 months after it. Older females conceived earlier than young ones. Females more than 2 years old were 53% of all fecund females, and produced 66% of all kids born. Productivity was estimated to be 83 or 94 kids per year per 100 females of breeding age, depending on the criteria used. Eviscerated body weight, body length, shoulder height, and horn length all showed clear sexual dimorphism, and all increased with age up to 3 years. Kidney fat increased with age only in males. At the time of sampling, female fatness was not related to reproductive state. In areas which had been hunted during the past decade the population was least dense, there was a higher proportion of young animals, the growth rate up to 1 year old was greater, and adults were larger, age for age, than elsewhere on the island.