| Summary: | Predators can respond to changes in prey abundance through either numerical or functional responses. Numerical responses may occur rapidly, where the predator numbers closely track those of the prey; alternatively, there may be time lags exhibiting slow changes in predator numbers. Functional responses occur when predators switch between prey species or redistribute to regions of high prey abundance. The Keweenaw Peninsula, in Michigan's Upper Peninsula, extends into Lake Superior. This region is northern coniferous hardwood forests and supports 17 species of carnivores. Potential small mammal prey were trapped, tagged, and released on 1 ha grids to estimate density. Data was recorded on age, species, gender, mass, location, and ectoparasites. Predator numbers at the site were estimated using tracks, scat, remote sensing cameras, and traps. The most common prey items were the woodland deer mouse (Peromyscus maniculatus) and the red-backed vole (Myodes gapperi); to date, seven species of carnivores have been recorded at the field site. Throughout the summer and fall of 2017, small mammal numbers were three-fold less than in 2016. Pine marten (Martes americana) were the most abundant predator at the site, with some of the highest densities reported in the literature. These high predator densities remained after the decline in prey, suggesting a time lag. Concurrently, prey densities remained high on an island in Lake Superior that is devoid of mammalian predators.
|
|---|