Relationship of Numbers of Nematode Parasites in Wild Rabbits, Oryctolagus cuniculus (L.), to Host Sex, Age, and Season

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Abstract
Using data from 2779 rabbits collected systematically from 4 sites in Australia, analyses were made of the numbers of the nematode parasites Graphidium strigosum, Trichostrongylus retortaeformis, and Passalurus ambiguus. For statistical analyses simple logarithmic transformation was equally as efficient as transforming according to a fitted negative binomial distribution; in many cases a negative binomial did not satisfactorily fit the data. Using dried lens weight as an age-indicator the relationship of numbers of each parasite to host age was examined. A simple positive linear regression of numbers of Graphidium on lens weight was very highly significant. For Passalurus a quadratic relationship was revealed. No relationship was detected between numbers of T. retortaeformis and estimated host age. The implications of these age relationships are discussed. Following correction of the numbers of parasites to allow for the different host population age structures, it was possible to examine relationships with factors such as season and host sex. Analysis of the data for G. strigosum revealed highly significant seasonal differences in abundance and even more significant between-sex differences [long dash]females harbored more parasites than males. At the most heavily infected and most heavily infected and most studied site, the main feature with both T. retortaeformis and P. ambiguus was highly significant sex times season interaction factors; during the breeding season females were much more heavily infected than males, a tendency towards the reverse being apparent in the nonbreeding period.