Analysis of weights and growth rates of an experimental colony of wild rabbits, Oryctolagus cuniculus (L.)

Abstract

A statistical analysis of the weights and growth rates of members of an experimental free-living colony of the Australian wild rabbit, Oryctolagus cuniculus (L.), the social organization of which has been studied in detail for two years, was carried out. Different seasonal conditions were the cause of very significant changes in the weights and growth rates of rabbits. Animals born at the beginning of the breeding season (June 1957 and April 1958) were heaviest and those born at the end (December 1957 and November 1958) were lightest. In some cases the difference in weights of juveniles at corresponding ages exceeded 30 per cent. Because only dominant and high-ranking does bred early in the season the heavier-weight groups were largely filled by their progeny. Statistical analysis of weights taken in 1957 revealed that at all ages from 30 to 150 days kittens of a dominant doe were heavier than kittens littered at the same time by a second-ranking or a thirdranking doe. The magnitude of the seasonal factors affecting growth was determined by the use of a simple mathematical model, and a relation between rainfall and the seasonal factors was found. The average weight of kittens born during the second breeding season was 200 g less than that of corresponding kittens born during the first season. The altered behaviour of the colony induced by increasing population was at least partly responsible for this disparity. Evidence was obtained that the weight of a free-living rabbit cannot always be used as a reliable indication of its age.