Host age predicts parasite occurrence, richness, and nested infracommunities in a pilot whale-helminth network.

Ecological data on marine mammal parasites represent an excellent opportunity to expand our understanding of host-parasite systems. In this study, we used a dataset of intestinal helminth parasites on 167 long-finned pilot whales Globicephala melas (Traill, 1809) from seven localities in the Faroe Islands to evaluate the extent to which the host's age and sex influence the occurrence, richness, and nested pattern of helminth parasites and the importance of individual hosts to the helminth community. We found positive effects of age on both the occurrence and richness of helminths. Older host individuals showed an ordered accumulation of parasites, as evidenced by the nested pattern in their composition. Males had a higher occurrence of parasites than females, but the richness of helminths did not differ between sexes. Our findings suggest that differences in host-parasite interactions in long-finned pilot whales result mainly from age-structured variations in biological and behavioral characteristics.