Associations of blacklegged ticks and European fire ants on Mount Desert Island

Guarnieri, Lucy; McBride, Sara; Gardner, Allison

From the abstract: "Rising blacklegged tick (I. scapularis) abundance has been documented in Maine for nearly thirty years. I. scapularis has been a growing concern in Acadia National Park, where tick habitat often coincides with the natural areas that are trafficked by visitors, residents and staff. A second pestiferous species, the invasive European fire ant (M. rubra), was first reported on Mount Desert Island as early as the late 1960s and is now infested in very high densities within isolated areas of MDI. Ants are known to prey on ticks, and it can be assumed that these two species, both of whom tend to inhabit leaf litter and underbrush in deciduous forests, must engage in some interaction. The aim of this project is to determine the effect of M. rubra on I. scapularis abundance and disease prevalence, which will help improve the development of management practices for both of these pests. To measure the effect of M. rubra on I. scapularis abundance, ticks were sampled at eight sites with high ant infestation, and eight control sites with no detectable M. rubra presence. The control sites and experimental sites were paired and in close proximity to each other and contained similar habitat features, including plants, canopy and groundcover. Ticks of all three life stages (adult, nymph and larvae) were collected in July and August. The difference in tick abundance at control vs. experimental sites was not statistically significant. In addition to their direct effects on ticks, M. rubra infestations can afflict small mammal populations, which in turn could alter tick and disease ecology, given that larvae and nymphs depend largely on mice to get the blood meals they require for molting. Track plates were deployed at each site in order to measure the effects of M. rubra on small mammal activity. Pathogen testing will be performed to determine whether the ants had a measurable effect on disease prevalence."