The fleas of house mice (Mus musculus L.) and ship rats (Rattus rattus L.) in forest of the Orongorongo Valley, New Zealand

The ectoparasites of introduced rodents in mainland New Zealand forests include several species of cosmopolitan flea that may be important in the population dynamics and future biocontrol of rodents. We describe a 2-rodent, 2-flea system that showed little change over 20 years. Ship rats (Rattus rattus) and house mice (Mus musculus) were snap trapped at fixed sites in the Orongorongo Valley, Wellington, for a study of their population ecology. The fleas Leptopsylla segnis and Nosopsyllus fasciatus were common on mice and rats respectively, and less common on the alternate hosts. Prevalence was described in relation to sex and age of the host, and to season and year. Male mice were more likely than females to carry L. segnis. Prevalence and intensity of infection mostly increased with age of host. Prevalence of both flea species showed modest seasonal variation, with a dip in autumn. Pregnant or lactating female rats and mice were less likely to have fleas than were non-breeding adult females. Prevalence did not vary positively with host density. We detected a slight overall increase in the prevalence of each flea species over the duration of the study. We conclude with some discussion of flea assemblages in New Zealand.