Some Population Parameters and Seasonal Changes in the Weights of Internal Organs of Rabbits, Oryctolagus cuniculus (L.), at Macquarie

Abstract

The sex ratio, age distribution and seasonal variations in body weight and weight of several internal organs of rabbits were studied, between December 1973 and February 1975 on subantarctic Macquarie Island. The sex ratio (male : female) was 1 : 0.84. Rabbits over 18 months old predominated in the population in summer 1973-74, but from April 1974 the population was composed equally of adults and rabbits less than 18 months old. The second half of the 1973-74 breeding season contained only 36% of the births of that season, but supplied 70% of the young rabbits that entered the population. Females weighed more than male rabbits in the summer but males were heavier in the winter. The mean weights of liver, kidneys and spleen in adult females were significantly heavier in the summer, when food plants were growing and the quality of food highest, than in winter. In adult males these mean weights were similar in summer and winter. Both males and females showed no significant difference in the mean weight of adrenal glands between seasons.