Skyrienė, G., Ulevičius, A. and Samas, A. 2011. Levels of Helminth Infection of Small Rodents in Two Interspersed Habitats – the Forest and Beaver Sites. Baltic Forestry 17(2): 299-307

Helminth infection in small rodents (Apodemus flavicollisand Myodes glareolus) was studied in forest and in beaver sites that were tightly spatially interspersed. Beaver sites were regarded as disturbed habitats inhabited by these two typical forests dwelling small rodent species. We tested the hypothesis that beaver sites, as disturbed habitats, can influence the abundance of infections with helminths, typical of forest rodent species. The composition of helminth species overlapped fully in the two tested habitats for M. glareolus (8 species of parasites) and nearly completely also for A. flavicollis (7 species in beaver sites and 6 species in the forest). M. glareoluswere more heavily infected with Syphacia petrusewiczi in beaver sitesthan in the forest in autumn and winter. The mean abundance of all helminths in M. glareolus was significantly higher in beaver sites only in the winter, with no significant differences in any other season. For A. flavicollis, we did not find statistically significant differences in mean abundance of helminths between the habitats neither for any particular helminth species nor for all helminth species taken together. We found some changes in the helminth community structure (as reflected in dominance hierarchies of helminths species) between the two studied habitats. S. petrusewiczi dominating markedly over the other helminth species in M. glareolus in the beaver sites, whereas dominance with this helminth was much weaker in the forest. For A. flavicollis, we found different dominant helminth species in each of the two habitats: Syphacia montana was strong dominant in beaver sites, but it was not found in mice dwelling in the forest, where Syphacia stroma dominated at the beaver sites. The patterns of taxonomic diversity of helminths and the distribution of parasites among host individuals did not reveal any significant differences between the tested habitats which were variable among host species and seasons. Our study has revealed habitat differences only in some aspects of the helminth infections of the two typical forest dwelling rodent species, whereas other tested parameters were highly variable and did not showed significant inequalities between habitats. These findings suggest a rather weak impact of the beaver sites on the epidemiology of helminth infections in typical forest dwelling small rodent species.

Key words: Apodemus flavicollis, Myodes glareolus, helminths, helminthinfection levels, forest, beaver sites, habitat disturbance