Predators And Prey - And People

By Mark Goodwin | November 2, 2001
From Missouri Conservationist: Nov 2001

During the first part of the 20th century, when wildlife management was in its infancy, most people considered predators a threat to game populations.

Their reasoning seemed logical. Because predators kill game animals, killing predators should result in more game. Guided by this notion, and with enthusiastic support from sportsmen, state and federal wildlife agencies implemented rigorous predator control programs. To further encourage public participation in these programs, these agencies often offered bounties for predator carcasses.

It wasn't long before wildlife biologists started noticing flaws in the idea of predator eradication. Focusing on large-scale removal of small fur-bearing predators like raccoons and opossums had proven ineffective. Eliminating large predators, coupled with a ban on hunting to protect deer populations, had proven disastrous. With no predators to control population growth, deer overpopulate and ravage their habitat and, eventually, fall victim to starvation and disease.

Learning from these failures, wildlife managers began to understand that predators and prey exist co-dependently. More important, they also began to recognize that habitat quality and quantity are the primary keys to maintaining healthy game populations.

Unlike emphasizing predator control, providing good habitat for wildlife proved economical. The success of habitat programs prompted government agencies to eliminate bounty programs. Only recently have wildlife biologists managed game populations by emphasizing habitat. This new direction and policy even resulted in some predators, such as birds of prey, receiving protected legal status.

Wildlife professionals recognize, however, that predators can be a factor in the declines of specific prey populations.

In the late 1980s and early 1990s, for example, duck numbers across North America dipped to a 50-year low. Researchers discovered that in the northern prairie states and Canada, small predators, mostly raccoons and skunks, were destroying up to 50 percent of all duck nesting attempts by eating eggs and killing nesting hens.

Even so, wildlife biologists found that the increased predation had links to habitat quality.

"Broad swaths of vegetation that surround potholes in the northern United States serve as ideal breeding habitat for ducks," said David Wissehr, a waterfowl biologist with the Missouri Department of Conservation. "Extreme dry conditions in the late 1980s and early 1990s resulted in many potholes drying up.

"Ground surrounding existing potholes dried to a point that allowed farmers to cut hay and plant crops closer to the water's edge," he added. "These conditions forced ducks to nest in concentrated numbers in the remaining thin bands of habitat along the edges of potholes, leaving nesting hens and their eggs easy prey for predators. Fortunately, a return of normal rainfall to these regions in recent years has allowed duck numbers to rebound."

Waterfowl aren't the only game species to suffer from predator problems. Across the Sierra Nevada Mountains in California, bighorn sheep populations have struggled recently because of diseases spread by domestic sheep. Reintroduction efforts to establish new herds have failed, not because of disease, but because of predation by cougars. State wildlife officials link this problem to a 1990 ballot initiative, passed by Californians, that outlawed killing cougars, even by wildlife officials, except in extreme cases. The action proved disastrous, both socially and biologically.

Without regulated hunting and trapping to control their numbers, cougars are now more numerous in California than ever. Not only are they causing problems for bighorn sheep, but cougar attacks on people also have increased, as have attacks on pets and domestic animals.

In Missouri, river otters were all but gone due to unregulated trapping and habitat destruction around the turn of the century. Restocking has restored their numbers statewide, but with a cost. Pond owners blame otters for fish kills, and some anglers believe otters kill too many game fish in Ozark headwater streams.

Historically, Missouri didn't have many natural ponds or lakes. That changed with settlement. Farmers built ponds to provide water for livestock. They also stocked ponds with fish. More than 300,000 farm ponds now dot Missouri's landscape, and otters do what comes naturally; they hunt where the hunting is good and easy.

"In ponds of a third of an acre or less that have little cover, otters are hurting fish populations," said Mark Haas, a Conservation Department fisheries biologist. "In winter, when fish are cold and sluggish, otters have little trouble catching them. And, to make matters worse, in small ponds, where fish are easily caught, otters often kill more than they eat, leaving dead fish on the bank."

People and Predators

In most natural situations, populations of predators and prey keep each other's population in check. When prey increases, predators increase, until they knock down the prey population, which results in a decrease in predators, allowing another spike in the numbers of prey.

Adding people to the mix, complicates the predator/prey relationship. In the prairie pothole region, for example, predators might not have had such a dramatic effect on duck reproduction had farmers left broad bands of vegetation around the potholes for duck nesting and rearing habitat.

In California, cougars might not threaten bighorn sheep and humans if hunters and trappers were allowed to help manage cougar numbers.

In Missouri, otters might not be so destructive if our abundance of stocked ponds didn't provide them such easy targets.

People's attitudes and behavior also have a direct affect on predator and, therefore, prey populations,

Trapping river otters, for example, is a logical and natural way to handle Missouri's river otter problem. However, anti-trapping activists oppose managing the population this way.

Fur prices are another way in which humans affect otter populations. When fur prices decline due to decreased demand, many trappers don't bother to target otters.

Others oppose hunting as a method of thinning deer herds, despite studies that show that in suburban areas where hunting is not allowed, deer quickly overpopulate and eat all available food, including expensive backyard flower gardens. The deer eventually suffer from malnutrition. Their growth is stunted, and they become vulnerable to disease. The deer also consume food needed by other wildlife, such as squirrels and songbirds.

Although our human presence results in predator problems, people can also become the solution to controlling animal populations. Although many people ignore this fact, in most places human hunters are safer, more predictable predators of deer than are cougars or wolves. It falls to us to harvest deer at a rate that keeps deer populations in check.

Finding ways for animals and people to coexist is one of the most complex problems facing wildlife management professionals in the 21st century. As greater numbers of people move to urban areas, they have less contact with nature. For them, nature's animals become either something too alien to tolerate or too cute to hunt or trap.

Any action to solve wildlife population problems, must recognize that

  • Wildlife must have homes.
  • Without checks on their numbers, wildlife will overpopulate.
  • Humans have replaced grizzlies, cougars and wolves as the predators most capable of naturally controlling animal populations.

Trapping, Politics and Game Management

Throughout history, people have trapped animals for their meat and hides. Trapping has long been one of the mechanisms that maintains nature's balance between predator and prey. Well-funded, politically active animal rights groups, however, oppose trapping as a wildlife management tool, and they pour money and manpower into ballot initiatives and advertising campaigns that allow the general public to vote on how, when and even if wildlife management and conservation agencies can use trapping to manage wildlife.

Such efforts have resulted in the banning of steel leghold traps in Massachusetts, Colorado, Arizona and California. Although these efforts came about through the legal, democratic process, they point out a widespread lack of understanding of population control mechanisms in the natural world.

This Issue's Staff

Editor - Tom Cwynar
Managing Editor - Bryan Hendricks
Art Editor - Dickson Stauffer
Artist - Dave Besenger
Artist - Mark Raithel
Photographer - Jim Rathert
Photographer - Cliff White
Staff Writer - Jim Low
Staff Writer - Joan McKee
Composition - Libby Bode Block
Circulation - Bertha Bainer