A pair of eastern wolves trek across the snow. New research details the different impacts wolves and coyotes have on local ungulate populations. Photo by University of Nebraska-Lincoln
April 20 (UPI) -- Without wolves, coyotes have become the de facto top dog throughout the Midwest and East Coast. But new research suggests coyotes lack the hunting prowess to fill the ecological void left by the eastern wolf.
The research, led by John Benson, an ecologist at the University of Nebraska-Lincoln, fits into the larger scientific effort to understand the roles predators play in shaping habitats and maintaining ecological balance.
It seems logical that coyotes and eastern wolves would fail to interact with and impact their habitat and local food chains in the same way, but measuring differences in the two species' ecological footprint isn't easy. Benson and his research partners decided to focus on the two predators' kill rates of deer and moose.
"Predator-prey interactions, like many ecological processes, are extremely complex, highly variable, and context-specific," Benson told UPI.
To shed light on these interactions, researchers tracked the hunting and feeding behaviors of several wolf and coyote packs in Ontario, Canada. Their observations showed wolves rely exclusively on large prey.
Wolves are several pounds heavier than coyotes and burn more calories during a hunt. Thus, they must feed on calorie-rich prey, such as moose and large deer. For wolves, moose meat makes up 54 percent of their ungulate intake, with white-tailed deer supplying the remaining 46 percent. Coyotes rely on moose for just 11 percent of their ungulate meat, with deer making up the difference.
Because wolves rely so intimately upon moose and deer as a food source, wolf and ungulate numbers rise and fall together. A growing wolf population kills more moose and deer, depressing ungulate numbers. In turn, the wolf population begins to shrink. Coyote numbers are more stable, as the canines can turn their attention to smaller prey like rabbits or scavenge for human waste.
For most conservationists, the goal is relatively straightforward: preservation and restoration of ecological balance. But measuring and understanding ecological balance isn't so simple.
However, improved models of predator-prey relationships and ecological systems, while not perfect, are offering some clarity.
"Absolutes are difficult in ecology and conservation -- and nearly impossible with predictive models of wildlife population dynamics," Benson said. "However, we are now able to build population models that will make predictions about the probability of a given population going extinct or declining relative to either the current conditions or some possible perturbation or management action."
Over the last decade or so, a multitude of studies have highlighted the ecological benefits offered by top predators. Research in Yellowstone National Park showed the reintroduction of gray wolf populations helped control ungulate populations, which in turn reduced grazing pressures on riparian habitat, or stream-side vegetation essential for vulnerable bird and fish species.
Other studies have highlighted the impacts of sharks and other top predators on coral reefs and local fish populations.
Benson's work, while just a start, has highlighted the unique role of the eastern wolf.
"We've shown that these wolves and coyotes exhibit different kill rates on deer and moose, and identified some key factors that influence this predation," Benson said. "The next steps will involve linking these predation patterns to the population dynamics of both predator and prey to obtain a more comprehensive understanding of the relationships between these species."
For conservationists, the logic remains the same. Ecological balance is the product of thousands of years, and should be preserved for its intrinsic and extrinsic values. But policy makers and wildlife officials often demand numbers to help make management decisions.
Benson and his fellow wildlife scientists won't ever be able offer certainties, but scientists are getting better at modeling predator-prey interactions and measuring the ecological impacts of specific species.
"The good news is people are trying to do these things -- asking bigger and better questions," Benson said. "And the technology we use in the field and the quantitative methods we use to build the models are improving every day. So as with much in science, the goal will be to keep asking the right questions, collecting the best data we can, and finding the most informative way possible to analyze the data."