The ecology of orally ingested parasites in ungulates of Etosha National Park.

摘要

Wildlife populations contain a diverse assemblage of parasites; hosts are often infected by multiple parasite species and parasites may infect multiple host species. I studied parasites infecting herbivorous mammals of Etosha National Park, Namibia, and examined how host-parasite relationships are modulated by host ecology, parasite interactions and environmental variability. The focal parasites were the orally ingested gastrointestinal strongyles (Nematoda, Strongylida) and Eimeria spp. (Protozoa, Eimeriidae).;Variation in host foraging behavior influences parasite prevalence and transmission. I used estimates of host intake rates and diet to examine variation in strongyle prevalence among host species. Species that require increased intake rates per metabolic weight exhibited higher strongyle prevalence, because either they are unable to combat these infections or the fitness cost of mounting a stronger immune response is too high.;Ecological questions about host-parasite systems often require estimates of parasite intensity. The main indirect method for quantifying gastrointestinal parasite intensity uses weight of fecal matter, and systematic variation in fecal water content could bias interpretation of propagule intensity patterns. From examination of springbok (Antidorcas marsupialis) and zebra (Equus quagga) feces, water variation influenced interpretation of sex differences in intensity, but not seasonal or age differences.;Disease dynamics are affected by seasonality, host age and immunity. I assessed temporal and host demographic variation in parasite prevalence and intensity of zebra, springbok, wildebeest (Connochaetes taurinus ) and gemsbok (Oryx gazella). Age-related parasite patterns provided evidence of variable protective immunity against parasite types. Strong seasonal differences in parasitism suggest a long dry season may limit survival of parasite environmental stages.;Finer taxonomic resolution in parasite identifications enhances the study of host-parasite relationships. I described three new species of Eimeria from springbok and then examined GI parasite interactions within hosts and among study areas. I found significant positive associations in parasites intensities and co-occurrences and that variation in host condition was best explained by combining the effects of multiple parasite types. Hosts from the study area with the least rainfall generally had reduced parasite prevalence or intensity. Understanding how parasites respond to environmental variability will provide critical insight into how climate change could alter host-parasite dynamics.