Predators And Prey - And People

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Published on: Nov. 2, 2001

Last revision: Nov. 9, 2010

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

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