Seed preferences and foraging by granivores at raccoon latrines in thetransmission dynamics of the raccoon roundworm (Baylisascaris procyonis)

摘要

Raccoons (Procyon lotor) habitually defecate at preferred sites (latrines). Feces at latrines often harbor eggs of the roundworm Baylisascaris procyonis, a parasite of raccoons that is pathogenic to numerous species of small vertebrates. Undigested seeds are also commonly found in raccoon feces, the composition varying with availability of seed types. Thus, feces at latrines may serve as a source of food and pose a mortality risk for small granivores. To examine this interaction, we manipulated the seed composition in feces at simulated raccoon latrines and tested for differences in vertebrate visitation rates as a function of seed type. Treatments involved placing seeds, including corn, cherry ( Prunus virginiana), dogwood (Cornus racemosa), and a combination of the three types, at simulated raccoon latrines. Using Trailmaster(TM) camera systems we documented 2406 vertebrate visits by 16 mammal and 11 bird species during 455 camera-nights. Small granivorous mammals, including white-footed mice (Peromyscus leucopus) and eastern chipmunks (Tamias striatus), were the most common visitors. Visitation by white-footed mice was significantly greater when corn, the most preferred seed type, was present in raccoon feces. Visitation by eastern chipmunks and other vertebrate species did not vary with seed type. Active foraging was documented for five vertebrate species and accounted for 10% of all recorded events. We conclude that raccoon latrines are routinely visited by a variety of vertebrate species, especially small granivores. Active foraging for seeds in raccoon feces is an important risk factor for transmission of B. procyonis to small vertebrates, and white-footed mice may suffer elevated rates of infection when corn is present in raccoon feces.