Ecologist says top predators restore balance to mountain states’ ecosystems
March 26, 2014
Steamboat Springs — George Wuerthner, a prolific author, ecologist and longtime critic of grazing on public lands, came to Steamboat Springs in the midst of Agriculture Week on Tuesday to talk about the role of predators, particularly wolves, in healthy natural ecosystems.
Wuerthner said the restoration of populations of top predators, including mountain lions and bears, in an ecosystem can restore its original health and actually provide life-giving support to other mammals and birds in times of critical need.
Noting that recent mild winters in Montana have reduced the amount of carrion available to ravens, magpies and wolverines, Wuerthner said wolf packs create carrion year round, which becomes a sometimes critical source of food for other species.
"It's particularly important in late winter and for mother grizzly bears just coming out of the den and looking for their first meal," he said.
Wuerthner's talk at Library Hall was hosted by the Yampa Valley Sustainability Council, the Sustainability Studies Program at Colorado Mountain College, Yampatika and Bud Werner Memorial Library. Wuerthner is a senior scientist and ecological project director for the Foundation for Deep Ecology.
Wuerthner said he hoped to get four key points across to his audience:
• The many ecological benefits created by top predators
• The fact that social ecology (the pack relationships among wolves, for example) are important to the management of predators and, in his view, that state wildlife agencies ignore social ecology
• Indiscriminate lethal control (hunting and trapping) exacerbates conflicts between humans and predators. Shooting the alpha male of a pack of wolves, for example, can reduce hunting success and lead to more and smaller packs within an area. And the reduced social structure and desperation for food can cause younger wolves to prey on livestock.
• Human hunters who harvest elk and deer, for example, are not a replacement for natural predation because animals like wolves and cougars tend to target very different individual animals than do hunters.
The positive effect that predators have on a larger ecosystem often is referred to as the trophic cascade.
The theory behind that much talked-about phenomenon, Wuerthner explained, is that when animals like wolves and cougars are removed from the top of a food chain, the numbers and behaviors of prey species are significantly altered. That shift in turn upsets the balance that once prevailed and harms the overall environment down to plants and invertebrates.
The effect can be measured in the return of wolves to Yellowstone, Wuerthner said. In their avoidance of areas where wolves den, elk are spending more time on higher, steeper slopes, which in addition leads to the perception among hunters that wolves have reduced the number of elk available to them.
"This is an important point," Wuerthner said. "Hunters say the wolves are killing off elk. There are more now than before (wolves) were reintroduced, but they are harder to hunt. If you are hunting in the old places you are used to, you're not going to see as many elk as before."
Hunting has been used as a tool to reduce elk populations to more sustainable levels in regions of the West, and in terms of sheer population numbers, that's effective, Wuerthner said. However, there's a downside, he said. Hunters tend to harvest prime bulls and fat young cows all in their reproductive years. That naturally reduces the overall fertility rates of an elk herd. Wolf packs, on the other hand, are apt to go for a target of opportunity and take down an older cow elk, who also happens to be past her reproductive years.
One study showed that the mean age of female elk shot by hunters is 6.5 years and those killed by wolves average 13.9 years, Wuerthner said.
Wolves have, however, aggressively reduced the number of surviving coyote pups by 30 to 40 percent in Glacier and Yellowstone national parks, Wuerthner said. Coyotes are rivals of wolves when it comes to hunting.
"Fewer coyotes leads to more fox — wolves don't care about foxes," he explained. "Coyotes feed on rodents, now the numbers of rodents have increased and there are more raptors in those areas feeding on rodents.”
Coincidentally, the Jackson Hole News and Guide reported March 19 on new research that confirms that coyotes aren't the only rival predators being targeted by wolves in the vicinity of Teton National Park.
New research released by the Teton Cougar Project shows that only 7 percent of Jackson Hole's mountain lions are surviving to adulthood. The project's Mark Elbroch revealed that only 34 of every 100 kittens born in the area in the past 13 years survived to age 6 months. But when the last six years were considered, the survival rate was halved.
Mapping the trend lines of the increasing wolf population in the study area against the declining survival rates of cougar kittens showed almost a 100 percent correlation, Elbroch said. Cougars that survive to between ages 6 and 18 months are far less likely to become the victims of other predators.
Wuerthner told his audience in Steamboat that just as indiscriminate hunting can disrupt the hunting habits of wolves, it can do the same with cougars, though they don't hunt in packs.
Mature male cougars tend to dominate large territories that overlap the smaller territories of the three or four females they breed with. When a hunter kills a trophy lion, the removal of that dominant individual allows younger, less effective hunters to occupy the territory.
It's most often these younger lions that interact with human society on the edge of cities like Boulder, Wuerthner said. Those are the desperate mountain lions, with few hunting skills, that are tempted by dogs left on the back porch of a house.