![]() "I was initially skeptical that it would be possible to detect something as diffuse in the forest floor as nutrients from dead animals," said Peterson, who has been studying the wolves and moose of Isle Royale for decades. Since large herbivores, like moose, are attracted to nitrogen-rich plants, the carcass sites become foraging sites, further supplementing soil nutrients from the urine and feces of the animals eating there. The nitrogen levels in plants growing on the carcass sites was from 25 to 47 percent higher than the levels at the control sites. Carcass sites also had an average of 38 percent more bacterial and fungal fatty acids, evidence of increased growth of bacteria and fungi. They found that soils at carcass sites had 100 to 600 percent more inorganic nitrogen, phosphorus and potassium than soil from surrounding control sites. They also analyzed the microbes and fungi in the soil and the leaf tissue of large-leaf aster, a common native plant eaten by moose in eastern and central North America. They measured the nitrogen, phosphorus and potassium levels in the soil at paired sites of wolf-killed moose carcasses and controls. ![]() "It's important because it illuminates another contribution large predators make to the ecosystem they live in and illustrates what can be protected or lost when predators are preserved or exterminated."īump and his colleagues studied a 50-year record of more than 3,600 moose carcasses at Isle Royale. "This study demonstrates an unforeseen link between the hunting behavior of a top predator - the wolf - and biochemical hot spots on the landscape," said Bump, an assistant professor in Michigan Tech's School of Forest Resources and Environmental Science and first author of the research paper. Joseph Bump, Rolf Peterson and John Vucetich report in the November 2009 issue of the journal Ecology that the carcasses of moose killed by wolves at Isle Royale National Park enrich the soil in "hot spots" of forest fertility around the kills, causing rapid microbial and fungal growth that provide increased nutrients for plants in the area. Our results suggest that the influence of predation on lower trophic levels may depend on the composition of predator communities.A large and unexpected one, say wildlife biologists from Michigan Technological University. The consistency in results between the two systems suggests that brown bear presence actually reduces wolf kill rate. Similarly, the presence of bears at wolf-killed ungulates was associated with wolves killing less often during summer in Yellowstone. In Scan-dinavia, wolf packs sympatric with brown bears killed less often than allopatric packs during both spring (after bear den emergence) and summer. On the contrary, our results showed the opposite effect. Although brown bears can monopolize wolf kills, we found no support in either study system for the common assumption that they cause wolves to kill more often. the number of days between consecutive ungulate kills) as a proxy of kill rate. ![]() We used long-term datasets from Scandinavia (Europe) and Yellowstone National Park (North America) to evaluate how grey wolf (Canis lupus) kill rate was affected by a sympatric apex predator, the brown bear (Ursus arctos). ![]() Trophic interactions are a fundamental topic in ecology, but we know little about how competition between apex predators affects predation, the mechanism driving top-down forcing in ecosystems.
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