Moose populations have been declining in their southern ranges across the United States. In addition to low productivity, habitat degradation, and a northward shift of populations, the deer brainworm (Parelaphostrongylus tenuis) is another hypothesis for the decline. White-tailed deer and terrestrial gastropods are the intermediate hosts for P. tenuis(and are unaffected by the parasite), and higher deer density in moose ranges may be associated with increased prevalence of the parasite in gastropods. Moose accidentally ingest gastropods while foraging, resulting in parasite transmission. This study evaluated environmental factors associated with gastropod abundance in Mount Baker. We used five gastropod sampling methods spaced 10m apart on four 100m transects located on Mount Baker in Saranac Lake, New York. We recorded gastropod abundance, and environmental factors (habitat type, soil pH, soil moisture, soil temperature, sunlight) at each sampling device during four site revisits. Based on previous studies, we expected that gastropod abundance would be greatest in wet, mixed coniferous-deciduous habitats.
Results/Conclusions
We used a mixed linear model, with site visit as a random variable and soil pH, soil moisture, soil temperature, habitat type, and substrate as fixed variables. Soil moisture had a strong effect on gastropod abundance (p = 0.02) while the other variables were insignificant in this model. Gastropods were most abundant in habitat types with very wet soils (p = 0.01). We also tested the relationship between soil moisture and trap type using a non-parametric Kruskal-Wallace test, but found no relationship.
Our results suggest that moose foraging in areas with high soil moisture may be more likely to encounter higher densities of gastropods, potentially increasing the risk of parasitic threats from deer brainworm if gastropods are accidentally ingested while foraging. Further studies should examine whether this relationship holds true across the Adirondacks and New York State where moose are present.