If Yellowstone and its wildlife were like some gigantic machine, elk would be its fuel
Yellowstone's elk are the primary prey base in the park and without prey, the predators of Yellowstone-- from the wolves to the grizzlies-- would not be able to exist. Today, with the fairly recent reintroduction of wolves back into this system, park managers are studying how wildlife is regaining the tenuous balance that exists between predator and prey.
Previous Wildlife Control Programs Disrupted the Balance
For many years, this balance was thrown off-kilter for Yellowstone wildlife. During the park's first fifty years, there was an active predator control program in the park. Coyotes in particular were shot or poisoned. In the early years, there was some active hunting of mountain lions using dogs. In the fall of 1934, this practice was finally discontinued, but not until after at least one predator, the wolf, was exterminated.
Today, all Yellowstone animals, those with sharp teeth and dull, are given the full protection of a more enlightened people. And, for the first time, a semblance of balance is entering the picture.
Wolf Reintroduction in 1995
Until 1995, there were no wolves in the park, but in that year, wolves captured and transported from Canada were released. That was the first year that things really began to change for the fuel called elk.
As more information is beginning to emerge, scientists are learning that it is not just which predators are preying upon elk, but how many. In Yellowstone, this is a very important realization.
Before the reintroduction of wolves, the predators included coyotes, black bears, grizzly bears, mountain lions and man. The latter element is and was crucial to equation, for elk hunting is big business in the states of Wyoming, Montana and Idaho. Each of these states has a fairly liberal elk hunting season in areas adjacent to the park. In the fall, when the elk begin to move out of Yellowstone's high country to lower lands surrounding the park, elk hunters take a good number of elk, particularly cow elk, from the population. Most of these animals are prime breeding age cows, and thus hunting helps managers keep elk numbers in balance with the carrying capacity of the land. The other predators also are important in managing elk numbers.
Spring is Elk Calving Season
In the spring, starting around the middle of May, elk cows begin to have their calves. The young calf elk provide an important food source to many predators, particularly grizzly bears.
Grizzlies are effective killers of elk calves and each spring, many of the park's grizzlies can be seen hunting the traditional calving grounds. While elk calves are fairly good at hiding, particularly in tall sagebrush, grizzlies can often sniff them out. Black bears, too, are relatively efficient predators of young calves and have been known to make a pretty good living hunting them.
Another very effective predator on elk calves are cougars, which biologists feel are far more effective at killing elk calves than are wolves. Finally, coyotes do account for some elk calf mortality. However, this latter predator is also prey-wolves kill coyotes in Yellowstone and this relationship between members of the canine family is just beginning to be understood.
Interestingly, some emerging work is revealing that coyotes are more prone to killing antelope fawns than elk calves. A new study has shown that in birthing grounds that have both coyotes and wolves, antelope fawn survival is higher than in areas with just coyotes. In other words, wolves are keeping a check on antelope fawn predation by coyotes.
The Strong Live On While the Weak Become Dinner
But the return of wolves into the system certainly has had an impact on elk numbers. In many cases, wolves are able to pull down injured, diseased or old elk far more effectively than any other predator in the park. In one documented case caught on film by a professional wildlife photographer, two wolves ran into a herd of elk, testing the prey for a vulnerable individual. At first, the film shows the wolves running randomly through the herd, when all of a sudden, they focus on one cow elk. As they zero in on this elk, close observation reveals that one of its hind legs is crippled. The wolves ignore all other elk as they weed this one cow out of the herd, and take it down. Examination of the remains by wolf experts including Dr. David Mech, the world's foremost wolf expert, revealed that the cow elk was indeed a weaker animal because she had a debilitating injury, arthritis in the hock joint. This was an injury that was not apparent to the human eye until after the wolves had selected it.
Weather is the Biggest Predator
Finally, it's important to give a nod to the most important element of all-weather. The importance of weather to ungulate populations such as elk cannot be overstated. Hard winters kill elk. Drought and the resulting poor feed kills elk. Weather is the most effective predator of all-without any predators, weather would still account for high elk mortality. Today, seven predators-wolves, black bears, grizzly bears, coyotes, mountain lions, man and, most important, weather-account for elk mortality. But even when elk die of starvation, their carcasses are used. The scavengers of the land-from coyotes to crows, to eagles-use this fuel and the cycle begins all over again.