The Trophic Cascade from the Gray Wolf

The Canyon Wolf Pack alpha pair lead their pups along a ridge near Mammoth Hot Springs in Yellowstone National Park, Wyoming. (Mike Cavaroc)
The Canyon Wolf Pack alpha pair lead their pups along a ridge near Mammoth Hot Springs in Yellowstone National Park.

I won’t waste your time in discussing political agendas and biases for and against the gray wolf. We all know that it is a controversial species that many feel is not at all welcome in nature, despite the fact that it has been an integral part of that very nature for tens of thousands of years. Virtually all of the biases against these mystical creatures comes from a simple misunderstanding of their very nature. In previous posts, I have discussed at length why more wolves are needed across the country and dissected the bias from both standpoints. One key factor I have never laid out in full detail, however, is the trophic cascade of events that happens once wolves reestablish a healthy presence in their chosen environment.

First of all, what exactly is a trophic cascade? Put simply, a trophic cascade is a series of natural events that occur from a predator’s presence that benefits life farther down the food chain. In this case, just by doing what a gray wolf is naturally supposed to do, life all around it flourishes, as outlined below. These are not theories or hopeful expectations of what could or might happen, rather, these are actual processes and reactions that have happened and have been documented through both eye-witness accounts and collected data from the last two decades in the Greater Yellowstone Ecosystem.

An Elk’s Role in the Trophic Cascade of Wolves

Bull elk who kept their antlers through the winter run through sagebrush in Grand Teton National Park, Wyoming. (Mike Cavaroc)
Bull Elk Running

One of the two most controversial subjects when discussing the wolf (the other being cattle ranching), elk are the primary ingredient when it comes to the trophic cascade. As the gray wolf’s first choice of food, wolves routinely and systematically weed out the sickest and weakest elk. This has been proven over and over again thanks to the autopsies carried out by Yellowstone National Park on the elk that have been preyed upon by wolves there. This leaves only the stronger and more agile elk alive to pass their genes on, making the entire herd stronger.

How Trees Flourish with Wolves Present

With a consistent threat of being chased around by wolves, elk are on the move more and more with any sign of danger. Since aspen, willow, and cottonwood tree sprouts are a good source of nutrition for elk, the movement of the herd allows these sprouts to grow into mature trees. In the absence of wolves, the elk become complacent, often staying in one location throughout the summer season, never allowing the sprouts to grow enough to become full trees. As a result, all of the aforementioned trees begin to suffer because none of the younger trees are given enough time to grow. Only with a healthy presence of wolves do all these trees begin to thrive again.

 (Mike Cavaroc)
New aspen tree growth

The image on the right clearly represents the difference in the trees due to the presence, and in this case, lack of presence of the wolves. The old, tall tree in the foreground was leftover from when wolves were last roaming the area before their extirpation in the 1930s, or sooner. After that there was no new aspen tree growth because of an exploding elk population and a lack of predators to keep the elk moving, thus the elk were free to graze on all the new sprouts. The large, extensive grove of trees that are smaller are all less than 20 years old, whose growth coincides with the reintroduction of wolves to the region. The image illustrates just how many aspens were trying to grow, but never could until the wolves came back. Of the thousands of new trees that would not even fit into this photo, there were less than a dozen adult trees alive, and there are groves just like it all over Jackson Hole and beyond.

Why Beavers Owe Thanks to Wolves

A beaver chews on an aspen tree branch in its pond in Grand Teton National Park, Wyoming. (Mike Cavaroc)
Beaver Eating Aspen Branch

With aspen, willow, and cottonwood trees all beginning to grow into healthy adult trees, beavers will now have plenty of food to build dams and lodges, in addition to having a plentiful food supply. Prior to the wolves’ reintroduction in Yellowstone National Park in 1995, the beaver was on the verge of going extinct in the area. Even by 2001, only one full beaver colony existed. By 2011, there were nine beaver colonies spread out throughout the park, all because wolves chased elk, thus allowing trees to grow which allowed beavers to use for food and construction.

How Beaver Ponds Benefit the Ecosystem

A moose calf drinks from a pond in Grand Teton National Park, Wyoming. (Mike Cavaroc)
Moose Calf Drinking in Pond

With a healthy beaver population come more beaver ponds. With more beaver ponds come more places for migratory birds to stop and rest along their journeys. Likewise, the riparian environments invite many other bird species to nest while also providing a drinking source for countless animals. The beaver ponds also act against erosion and provide even more nourishment for vital willow trees, which the beavers themselves depend on, as well as moose. Though moose can become prey for wolves, moose also depend heavily on willow leaves and pond vegetation in the warmer months, in addition to having a cool place to lay down and keep out of the heat, all provided by beavers. Calmer portions of the creeks also provide a comfortable environment for otters, fish, and amphibians.

Why Grizzly Bears Partly Owe Their Recovery to Wolves

Grizzly Bear #610 of Grand Teton National Park shows one of her three cubs how to rip down an aspen tree. (Mike Cavaroc)
Grizzly Bear and Cub on Aspen

Wolves are the only predator that will routinely and regularly take down adult, big game wildlife larger than the average deer. With the carcasses that they leave behind, a plethora of other animals benefit. The grizzly bear was never fully extirpated from the lower 48 like the wolf was. A very solitary animal, a grizzly bear can survive deep in treacherous terrain, easily evading humans. As a result, a small presence managed to survive in the 20th century in the most remote areas of Yellowstone National Park. Their recovery into the latter half of the century was still remarkably slow and sightings were very rare. Enter the gray wolf. Within a matter of years, reports of grizzly bear sightings began to come from as far away as Grand Teton National Park to the south by the end of the century. Now, Grand Teton National Park boasts equal, and often times better, grizzly bear viewing than its northern neighbor, Yellowstone National Park. When wolves take down an elk, they gorge themselves with up to 20 pounds of meat each before retreating back to the den, often leaving a lone wolf to guard the carcass, unless the pack itself has had enough. That still leaves hundreds of pounds of nutrition for any other animal capable of chasing away a wolf, particularly a grizzly bear. With the extra nourishment during spring and summer months for grizzlies and their cubs, the grizzly bear population began to explode around the region, paralleling the wolf population while this other vital predator began to help balance out the ecosystem.

Coyotes Return to Scavenging with Wolves Present

A coyote quietly sneaks through snow and sagebrush in Yellowstone National Park, Wyoming. (Mike Cavaroc)
Coyote sneaking through snow

Coyotes are not predators. If you see a pack of coyotes hunting an animal, that is a sure sign that that ecosystem has a severe lack of predators. Coyotes by their very nature are scavengers and rodent hunters. In areas where wolves have been, or are, absent, coyotes are frequently seen harassing animals that they are simply not equipped to take down. Doing so is a clear indicator of how desperate they are for food. With wolves present, the carcasses that they leave behind are plenty of food for coyotes to eat from and maintain a healthy life until the next meal, even after grizzly and black bears have had their fill. Similarly, wolves kill any coyotes they find in their territory. This leads to a smaller coyote population, allowing for many other species to establish a more meaningful presence. Hares and even young big game, such as deer and pronghorn, are given more of a chance to grow into adults. Fewer coyotes also means more squirrels and ground rodents, leading to a much healthier population of birds of prey such as bald eagles and owls.

With Less Coyotes, Foxes Have More Presence

A red fox curls up for a nap on the snow in Grand Teton National Park, Wyoming. (Mike Cavaroc)
Fox sleeping in snow

Thanks to a smaller coyote population, foxes now have the opportunity to feed on more wildlife, such as hares and ground-nesting birds such as killdeer. With foxes preying on many of those animals, even the vegetation on the ground is also affected. Bugs that live on those plants are also affected because of the ground-nesting birds. As a result, this creates more balance in the ground vegetation itself.

With Wolves Nearby, Cougars Return to Their Natural Habitat

Mountain lion kittens sit cautiously behind their mother in Grand Teton National Park, Wyoming. (Mike Cavaroc)
Mountain Lion Mother and Kittens

Without the presence of wolves, mountain lions often venture into open valleys to find their prey, a place that is very outside of their normal habitat. Naturally, cougars prefer dense, wooded areas with plenty of trees. Without another significant predator to take down big game adults, the mountain lions often had no choice but to wander into valleys to find their prey. Upon the return of wolves, however, deer began to flee back into the trees. In addition, the wolves would take over the mountain lion carcasses lying in valleys. This led to a shift in both the mountain lions and their prey as both fled back into the woods. With wolves back in their territory, mountain lions can now return to being the dominant predator in the forests. (Bears are often found in forests, but prefer to hunt and graze in meadows.)

Other Locations Suffering from a Lack of a Trophic Cascade

The canyon walls of Zion Canyon begin to cast shadows across Zion Canyon in Zion National Park, Utah. (Mike Cavaroc)
Zion Canyon from Angel’s Landing

Anyone who has been to Zion National Park has most likely visited Zion Canyon and seen the lush cottonwood trees lining the Virgin River. Did you know, however, that those cottonwood trees may not be around forever? Heavy human traffic in Zion Canyon has forced the historically rich mountain lion population to flee the area, leaving the native deer population to explode and casually graze wherever they want on whatever they want. This is having a devastating effect on new cottonwood trees as well as the river channel itself. Similar catastrophes are occurring completely under the radar in Yosemite National Park and many other areas as well.

So how do you dissipate human traffic to a protected area? Protect more areas. Millions of people plan out vacations every year around protected areas such as national parks. If there were at least twice as many of them, more people would have more options to visit, and from there more solutions could be found to help reestablish a healthy ecosystem. It certainly would not fix the issue alone, but it would definitely be a good first step in the right direction, while at the same time bringing an enormous boost to the economy.

It is truly remarkable how one animal affects an entire ecosystem. Take that one animal out of the equation, and everything you have just read falls completely apart. Gray wolves, and in many areas cougars, are the cornerstone of a healthy ecosystem and anyone who will tell you otherwise has simply refused to educate themselves on how the natural world operates in perfect harmony when it is allowed to. More protection and more tolerance of our predatory treasures are not just good ideas, but undeniably required in order to preserve and maintain the natural beauty of North America.


One thought on “The Trophic Cascade from the Gray Wolf

  1. Pingback: How Yellowstone wolves help other wildlife | Dear Kitty. Some blog

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