Graphidium strigosum and Trichostringylus retortaeformis in a confined population of wild rabbits

Abstract

Replicated rabbit populations were maintained in experimental enclosures at each of three densities (approximately 12.5, 25, and 50 rabbits per ha); in addition, populations were maintained at a density of about 50 per ha but in enclosures of three different sizes (about 0.1, 0.2, and 0.4 ha). Altogether 230 rabbits commenced the experiment. Towards the end of the breeding season all the surviving rabbits (or their replacements) were killed and counts made of the numbers of G. strigosum and T. retortaeformis. Statistical tests were done relating the numbers of these parasites to the treatment to which their hosts had been exposed and to a range of factors that had been measured either during or at the termination of the experiment. Numbers of G. strigosum varied in relation to the treatment to which their hosts were exposed, in particular to the length of time that the rabbits had been under the conditions of the experiment and to factors directly related to the treatment, especially rabbit density and the amount of social contact with other rabbits. These extrinsic factors had a much less marked effect on the numbers of T. vetortaeformis in the rabbits. Male rabbits of low social status carried significantly more T. uel'ortaeformis than did their more dominant counterparts. It is suggested that this was the result of social factors affecting the susceptibility of these subordinate animals to infection with this parasite.