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Ecoscenario: Yellowstone National Park 4/16/03 3:25 PM The most abundant large mammal in Yellowstone is the elk. Their numbers vary with the seasons. In summer there are seven or eight herds, totaling almost 30,000 animals. In the winter, many elk migrate out of the park, many to an elk refuge near Jackson, Wyoming. About 15,000–22,000 elk winter in the park. Male elk, or bulls, are often solitary. Courtesy of National Park Service Courtesy of Teri Dannenberg Female elk (cows), calves, and yearlings stay in herds that are led by a dominant bull elk. On the rocky cliffs of Yellowstone's mountains you might spot bighorn sheep. These sheep can walk on the steep cliff faces, making it possible to avoid less-nimble predators. In the densely wooded slopes bears search for the sweet fruit of wild huckleberries. Down in the flat grasslands, bison and pronghorn antelope graze on grasses and sedges. In the northern sections of the park, the snow is not as deep in winter. Here you might see a bobcat, because bobcats avoid deep snow. Wildcats, like bobcats and lynx that also occur in the park, are rarely seen. The cats are most active at night, and avoid people. Courtesy of Teri Dannenberg Two bighorn rams facing off before fighting by crashing into each other with their horns. Courtesy of Teri Dannenberg Marmots make their homes under rocks and rubble. Black bears, brown bears, coyotes, and wolves are difficult to spot, but sightings are more common now that their numbers are increasing. Wolves can be heard calling to each other in the night. Annual productivity, or the amount of energy provided by the producers in this ecosystem, is high, 3600 kilocalories/ square meter/year of plant material. file:///Ecoscenario/yellow/content.html Page 10 of 15
Ecoscenario: Yellowstone National Park 4/16/03 3:25 PM ISSUES In the early 1900s in an effort to stablize the herds of elk, bison, and mule deer, predators ( wolves, cougars, and coyotes) were removed or eliminated from the park. By the time it was discovered that it was not predators, but reduction of winter grazing lands, that had caused the decline, the population of wolves had become dangerously small. Wolf sightings became rarer and rarer until 1970, when no wolves were reported in Yellowstone National Park. The reintroduction of wolves has been an issue at Yellowstone National Park. National park policy calls for the restoration of a species when sufficient habitat exists to support the population, management can prevent threats to outside interests, the restored species is almost identical to the lost species, and the loss of the species is the result of human activities. Wolves were in the Yellowstone ecosystem before the park was founded in 1872. Wolf-removal programs were instituted to benefit the elk, deer, and moose. By the 1940s sightings of wolves had become rare. In the 1970s there was no evidence that breeding pairs of wolves remained in Yellowstone. The wolves were gone, but the population of elks continued to decline. Yellowstone National Park began managing the elk population, and their numbers increased from 3100 in 1968 to over 30,000 today. Park managers say that elk are returning the Yellowstone ecosystem to a natural balance, in which elk numbers are limited by food supply. Others worry that there are now too many elk and that they are changing the landscape of Yellowstone from forest to elk grazing land. Elk browse on tender aspen saplings, reducing the number that mature. This disrupts the normal forest succession in Yellowstone. In 1978 the U.S. Fish and Wildlife Service proposed the reintroduction of wolves into the Yellowstone ecosystem. It was predicted that the populations of elk, bison, mule deer, and moose would be regulated by wolf predation. Ranchers and hunters outside the park immediately opposed reintroduction. Ranchers were worried that wolves would find cattle and sheep easier prey than elk. Hunters were worried that elk populations would be reduced and that fewer hunting permits would be issued. file:///Ecoscenario/yellow/content.html Page 11 of 15
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