Wolves Have Unexpected Effect on Elk Populations
Elk populations in the Yellowstone area are declining and scientists from Montana State University have been trying to identify the cause. Wolves, one of the elks’ natural predators, were reintroduced to Yellowstone in 1995. Although some elk are killed directly by wolves, scientists have found that the wolves have also had an indirect effect on elk populations. Where wolves share land with elk, elk have altered their foraging behavior to avoid confronting their predators. This change in foraging behavior has meant that elk are not receiving the nutrition they need and as a result are producing fewer calves each spring.
Instead of grazing on grass in open meadows where they are vulnerable to attacks by wolves, elk now opt for the greater protection of wooded areas where they browse on twigs, branches and shrubs in the relative safety of forest cover. This dietary change is significant—grasses are rich in nutrients and are a high quality food source, especially in winter when it is crucial the elk obtain adequate food supplies. But the twigs, shrubs, and branches they feed on when in wooded areas are a lower quality food source than grasses. During the winter, the elk that feed on woody vegetation cannot obtain enough food to maintain their body weight. As the winter months press on, they loose weight and grow weak. When spring comes, they bear fewer calves.
References:
- Greater Yellowstone Elk-Wolf Study Shows Elk Having Fewer Calves Due to Changes in Nutrition (Eurekalert)
Photo © BirdofPrey / iStockphoto.
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