Social behaviour of an experimental colony of wild rabbits, Oryctolagus cuniculus (L.) IV. Conclusion: outbreak of myxomatosis, Third breeding season, and starvation

Abstract

This paper reports on the final 19 months of observations of the social behaviour of an experimental colony of the Australian wild rabbit, Oryctolagus cuniczclus (L.), at Gungahlin, A.C.T. An outbreak of myxomatosis, socid developments during the third breeding season, and a population crash due to starvation are outlined. Of the 19 rabbits that survived infection with myxomatosis 15 were descendants of the original dominant doe. They formed four separate sooial groups. During the period May-December 1959, 89 litters (368 kittens) were produced by the population, which at the onset of the breeding season included eight does. Of the kittens 119 (32.3%) survived until January 1960. Survival was highest (more than 80%) among kittens born early in the season and lowest (9.5%) among those born in December. Intra-uterine mortality was greatest in July when 25% of the litters were lost. It was low, however, compared with that in the preceding year, when the population density in December was 47% higher. Starvation reduced the population to 42 in April-May 1960. Resistance to starvation was proportional to age. The dominant rabbits, being older, survived best. In several instances a remarkable resistance to starvation was shown. Up to 55% of the pre-starvation body weight was lost by animals that died; some survived after a loss of up to 45%.