Yellowstone National Park

Animals & Wildlife of Yellowstone

Yellowstone is widely considered to be the finest megafauna wildlife habitat in the lower 48 states. Animals found in the park include the majestic American bison (buffalo), grizzly bear, black bear, elk, moose, mule deer, pronghorn, bighorn sheep and mountain lion (puma). Rivers in the Yellowstone drainage comprise the core range of the cutthroat trout subspecies known as Yellowstone cutthroat trout, a fish highly sought by anglers yet one that has faced several threats in recent years, including the illegal intentional introduction of lake trout, which consume the smaller cutthroat trout; the ongoing drought; and the accidental introduction of a parasite which causes a terminal nervous system disease in younger fish, known as whirling disease.

The relatively large bison populations that exist in the park are a concern for ranchers who fear that the bison can transmit bovine diseases to their domesticated cousins. In fact, about half of Yellowstone's bison have been exposed to brucellosis, a bacterial disease that came to North America with European cattle and may cause cattle to miscarry. The disease has little effect on park bison and no reported case of transmission from wild bison to a visitor or to domestic livestock has ever been filed. But since the possibility of contagion still exists, the State of Montana believes its "brucellosis-free" status may be jeopardized if bison are in proximity to cattle. Montana had approved a bison hunt for the fall of 2005, with 50 licenses issued to shoot bison that have left the park. Elk also carry the disease, but this popular game species is not considered a threat to livestock.

To combat the perceived threat, National Park personnel regularly harass bison herds back into the park when they venture outside of park borders. Animal rights activists state that is a cruel practice and that the possibility for disease transmission is not as great as some ranchers maintain. Ecologists also point out that the bison are just traveling to seasonal grazing areas that lie within the Greater Yellowstone Ecosystem that have been converted to cattle grazing (most of these areas are also within United States National Forests).

After the wolves were extirpated from Yellowstone, the smaller cousin of the wolf, the coyote, then became the park's top predator. However, the coyote is not able to bring down any large animal in the park and the result of this lack of a top predator on these populations was a marked increase in lame and sick megafauna.

Starting in 1918, in an effort to protect elk populations, the Director of the Park Service ordered “extermination of mountain lions and other predatory animals” in Yellowstone. Park Service hunters carried out these orders and by 1926 they had killed 122 wolves. By this time wolves were all but eliminated from Yellowstone.

By the 1990s, the Federal government had reversed its views on wolves. In a controversial decision by the U.S. Fish and Wildlife Service (which oversees threatened and endangered species), wolves were reintroduced into the park. Before 1994 there were no wolves in Yellowstone. The wolves that were reintroduced in 1995 and 1996 thrived and there are now over 300 of their descendents living in the Greater Yellowstone Area.

However, ranchers in surrounding areas are concerned about wolves that venture outside the park and prey on their livestock, especially sheep and cattle. For the most part, wolves kill what they were taught to kill as pups, so they tend to prey on elk rather than sheep, but once a wolf pack begins eating sheep and training the pups to eat sheep, there is little recourse but to destroy the offending pack members. Ranchers are compensated for their losses if they can prove that wolves killed the livestock, but they contend that it is often difficult to prove that the kills were not made by coyotes or wild dogs.

Reintroduced wolf packs do not carry endangered species status, so ranchers can kill wolves that threaten their herds, but wolves relocating from Canada on their own have begun to merge with the Yellowstone population, making it difficult to discern which wolves are protected and which are not.
The National Park Service was generally not in favor of the reintroduction, citing evidence that wolves had already begun to return on their own, reestablishing themselves in very limited numbers prior to the wolf reintroduction. Wildlife biologists employed by the National Park Service had documented rare sightings made personally and from eyewitness accounts. It was a quiet concern that the compact agreed on by federal agencies and the states in which Yellowstone is located would ultimately provide less protection to the wolf, because the threatened status would be amended to appease local interests such as ranchers who would not likely face prosecution under the reintroduction agreement.

In Yellowstone's hot waters, bacteria form mats consisting of trillions of individual bacteria. The surfaces of these mats assume bizarre shapes, and flies and other arthropods live on the mats, even in the midst of the bitterly cold winters. Scientists thought that microbes there gained sustenance only from sulfur, but scientists from the University of Colorado at Boulder discovered in 2005 that the sustenance for some species is molecular hydrogen - although there is evidence that this may not be the case for all of these diverse hyperthermophilic species.

Invasive species

Lake trout are an example of an invasive species of fish that is decimating the native cutthroat trout population in Yellowstone Lake.

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