|HOME SCHEDULE AUTHOR INDEX SUBJECT INDEX|
Tri-trophic interactions of wolves, deer, and plant communities in the Northern Wisconsin and Michigan.
Anderson, Dean*,1, Rooney, Thomas1, Turner, Monica1, Waller, Donald1, Wydeven, Adrian2, Wiedenhoeft, Jane2, Beyer, Dean3, Alverson, William4, 1 University of Wisconsin-Madison, Madison, WI, USA2 Wisconsin Department of Natural Resources, Park Falls, WI, USA3 Michigan Department of Natural Resources, Marquette, MI, USA4 The Field Museum, Chicago, IL, USA
ABSTRACT- The effect of high-density deer populations on plant communities has been well documented. However, few studies have examined whether top predators may mitigate this effect spatially. We used data from Northern Wisconsin and Michigan to address the following questions: (1) is there an inverse relationship between deer (Odocoileus virginianus) and wolf (Canus lupus) densities across the landscape?; (2) does species richness of forbs vary as a function of the density of wolves in the area?; and (3) does the biomass of grasses, forbs, and shrubs vary with wolf density? Radio-telemetry and ground-tracking data of wolves were used to identify locations of wolf packs. GIS analysis was used to determine the center point of wolf territories, and the inverse of the distance from the center point was used as an indicator of wolf density. Deer fecal-pellet surveys were conducted at 46 locations to estimate deer densities relative to wolf pack locations. Vegetation was sampled in the Chequamegon National Forest, Wisconsin to quantify the species richness of forbs, and the biomass of forbs, graminoids and shrubs. Results indicate a significant inverse relationship between deer and wolf densities. In coniferous forests and cedar swamps, habitats used extensively by deer, forb species richness had a hump-shaped relationship with wolf density, indicating a potential intermediate-disturbance-hypothesis mechanism. In cedar swamps, biomass of all forb species and shrub species that experience high rates of deer browsing was positively related to wolf densities. In contrast, graminoid biomass was negatively related to wolf densities. These results suggest that wolves mitigate spatially the effect of an over-abundant deer population on vegetation communities.
Key words: predator, plant communities, trophic interactions, herbivore