Relationships among Prey Abundance, Habitat, and American Marten in Northern Maine
- Lachowski, H. Joseph
University of Maine
American marten (Martes americana) are thought to be associated with forested landscapes that include mature, conifer-dominated forests. Further, marten preference for mature conifer stands has been associated with greater prey densities and volumes of coarse woody debris relative to deciduous and regenerating stands. In a northern Maine forest preserve, however, marten extensively used mature mixed coniferous-deciduous and deciduous dominated stands, as well as stands defoliated by spruce budworm (Choristoneura fumiferana). Further, research on an adjacent site characterized by extensive forest harvesting indicated that marten used mixed and deciduous forests, and selected against regenerating clearcuts. North America studies have frequently suggested that small mammal populations are also positively associated with presence of coarse and woody debris. I examined marten food habits and habitat features associated with small mammal captures to evaluate the hypothesis that marten select habitat in response to differences in macro- and micro-habitat selection by their principal prey.
Percent occurrence of food items was quantified for 219 marten scats. Red-backed voles (Clethrionomys gapperi) and deer mice (Peromyscus maniculatus) occurred in 45.5% and 32.3% of scats, respectively. Snowshoe hare (Lepus americanus) and red squirrel (Tamiasciurus hudsomicus) were more frequently consumed during winter (35.3% of winter scats) than during summer (17.5%). Berries comprised a major component of marten diets (> 71% occurrence in scats) during summer and fall. Marten seemed to select voles and mice in proportion to their relative abundance. Red-backed voles and deer mice accounted for 49% and 23% of live-trapped small mammals, and occurred in 45% and 32% of marten scats.
Small mammal populations declined 67% between 1995 and 1996. During both years, deciduous and mixed stands had greater small mammal abundance than coniferous and regenerating stands. Abundance of voles and mice in budworm-killed stands declined only 27% between years, whereas population declines were more drastic (88%) in regenerating stands. Snowshoe hare density was greater in regenerating and budworm-killed stands than in deciduous or mixed stands. Budworm-killed stands may be important to marten because of their prey base, abundance of coarse woody debris, and because they retain some mature overstory characteristics.
Small mammal abundance was greater in mature stands than in regenerating or budworm-killed stands, and was correlated with variables reflecting stand maturity (canopy cover, dbh, stump volume). In this study, small mammals did not seem to select habitat based on coarse woody debris, perhaps because dead woody material was sufficient in all of the stand types.
Extensive use of mature mixed and deciduous stands by marten in northern Maine may result from higher prey abundance compared to regenerating and coniferous stands. Small mammals were positively correlated with habitat features associated with forest age. Both marten and their small mammal prey have affinities for stands with mature characteristics, but also utilize regenerating, insect defoliated stands with residual canopy cover, snags, and live trees. Thus, forest harvesting practices that retain some structural attributes of mature forests may be beneficial to martens and other forest predators that utilize red-backed voles and deer mice as principal prey.
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