November 6, 2009, 3:28 pm
Moose eat plants; wolves kill moose. What difference does this classic predator-prey interaction make to biodiversity?
A large and unexpected one, say wildlife biologists from Michigan
Technological University. 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.
“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. “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.”
Bump and his colleagues studied a 50-year record of more than 3,600
moose carcasses at Isle Royale. They measured the nitrogen, phosphorus
and potassium levels in the soil at paired sites of wolf-killed moose
carcasses and controls. 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 found that soils at carcass sites had 100 to 600 percent more
inorganic nitrogen, phosphorus and potassium than soil from surrounding
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.
The nitrogen levels in plants growing on the carcass sites was from
25 to 47 percent higher than the levels at the control sites. 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.
