Social behaviour of an experimental colony of wild rabbits, Oryctolagus cuniculus (L.) III. Second breeding season

Abstract

Developments during the second breeding season of an experimental colony of Australian wild rabbits, Oryctolagus cuniculus (L.), are described. The 67 survivors from the first season, including 33 does, formed eight groups, each with its own dominance-hierarchy (established after severe fighting) and group territory. The existence of two types of territory-grazing and shelter-was clearly demonstrated by their behaviour. All groups were of mixed parentage, but the male progeny of the original dominant doe were always dominant. Only the dominant does littered in April, May, and June, and used the permanent warrens established before the beginning of t'he breeding season. Progeny of the original lowest-ranking doe were generally subordinate. They were predisposed to pakhogenic factors and t'heir breeding was inhibited. Subordinate does did not litter until late in the season, using isolated breeding stops dug just before parturition. Possession of burrows, and the quality of burrows, determined breeding success. Intra-uterine mortality was low at the beginning and the end of the season, and highest (81 per cent.) in July. Seventy-five litters (395 kittens) were dropped during the period April- Sovember 1958; 106 kittens (27 per cent.) survived until January. Survival was highest (more than 70 per cent.) among kittens born to dominant does in April and May; it fell as the season advanced, and was lowest (5 per cent.) among kittens born in November. Since the subordinat'e does did not start to breed until the second half of the breeding season only a small proportion of their progeny survived. Pasture deterioration, leading to shortage of food, was apparently the most important factor influencing the kittens' behaviour and mortality. The mothers neglected suckling and the kittens left the nests prematurely. Pathological findings are given for most of six adult's that died during the season. Staphylococcus aureus and Pasteurella septica were isolated.