When discussing the conservation of wolves, it is important to understand why we should bother to save wolves from extinction. They attack and eat livestock and pets, causing economic losses to farmers and ranchers and anguish to pet owners, and they compete with human hunters for game such as elk. Are they merely a pest species?
To answer this question, we need to know something about the scientific discipline of community ecology. In colloquial usage, ecology is another word for environmentalism, but as a scientific discipline, ecology is the broadest concern of biology, the science of life. Whereas other branches of biology are concerned with cells, organs, or individual animals and plants, community ecology studies how different species of plants, animals, and microorganisms interact with each other within a biological community. A community might be a forest, a stretch of desert, a national park, a portion of the seashore, someone’s backyard, and so on.
Most healthy, self-sustaining biological communities have four types of members:
- Producers. These are either plants or green algae that convert non-living matter into organic substances that they incorporate into their bodies through the process of photosynthesis. They feed everyone else in the community, directly or indirectly.
- Primary consumers. These organisms, mostly animals, eat the producers. Herbivores, such as cows, sheep, and elk, also plant-eating insects.
- Predators. These organisms eat other consumers. Carnivores, such as mountain lions, wolves, snakes, and ladybug beetles.
- Decomposers. Mostly microorganisms and fungi as well as insects that eat dung. They break down the tissues of dead plants and animals and animal excrement and make the chemicals found there available as food for the producers. Nature’s great recyclers.
All four classes of organisms are important to a healthy ecosystem. If one class is diminished, an imbalance occurs which disrupts the nutrient cycle, makes it harder for other species to thrive, and reduces biodiversity. For example, without decomposers like bacteria, dead plant and animal matter can’t be recycled for plants to use, and the nutrient cycle is disrupted. Without plants to make food, primary consumers cannot survive, and soon, neither can the predators that feed on them. Without predators, consumers become too numerous and become destructive of the plant species off which they feed.
National Public Radio’s Morning Edition Show recently broadcast a story on this topic entitled When Big Carnivores Go Down, Even Vegetarians Take The Hit. The broadcast is a little more than three minutes, and you can read it (and listen to it) by clicking here.
A good example of this discussion is the Yellowstone Park community. Wolves were exterminated there as they were in most of America in the 1920’s, but were reintroduced in 1995. First, here is a link to a video on the topic entitled Predators by Bill Ripple, which you can view by clicking here.
Here is an excellent essay on wolves in Yellowstone that appears on the website of the Wyoming chapter of the Sierra Club, which I am reprinting here, in compliance with the Sierra Club’s Terms and Conditions of Use. It was written by members of the Western Wolf Coalition. It explains what the wolf has done for the Yellowstone Park ecological community:
Ecological Benefit of Wolves
Wolves play a vital role in maintaining the health and sustainability of the landscape in the greater Yellowstone region and our western lands. They are a keystone species, one that has a disproportionate impact on its environment relative to its abundance. Since their return in 1995, wolves have benefitted this ecosystem by regulating prey numbers and movements—allowing streambank habitats to recover, reducing densities of coyotes, and providing food for scavengers.
The most recognized and well-documented ecological benefit of wolves is that they have resumed the important role of maintaining healthy wildlife herds in the northern Rockies by selecting young, old, physically impaired, or diseased animals5. By reducing prey numbers, dispersing these animals on the landscape, and removing sick animals, wolves also may reduce the transmission and prevalence of wildlife diseases such as chronic wasting disease and brucellosis7.
In addition to improving the overall fitness of wildlife herds, wolves have also altered the behavior of their prey, leading to a cascade of beneficial effects on the landscape. In the absence of wolves, elk tended to browse heavily in the open flats along rivers and wetlands, since they did not need to evade predators by seeking thicker cover. Without fear of wolves, elk over-browsed the vegetation inhibiting the growth of new trees. Since the reintroduction of wolves in Yellowstone, elk spend more time in the safety of thick cover or on the move6. As a result, riparian areas and aspen groves that had been suppressed by decades of over-browsing are regenerating, improving habitat for species like beavers and songbirds3. Beavers, which create wetland habitats with their dams, have improved water quality in streams by trapping sediment, replenishing groundwater, and cooling water.
Species that rely on healthy riparian habitats and benefit from the presence of wolves in Yellowstone National Park include:
- Yellowstone cutthroat trout and other native fish
- Waterfowl (ducks, geese, trumpeter swans)
- Songbirds (such as warblers, wrens, and thrushes)
Small mammals (such as beavers, muskrats,
and other rodents)
- Insects, amphibians, and countless other species3,6
Wolves and Coyotes
In the absence of wolves, coyotes became a top predator in the ecosystem, but they are not large enough to regulate elk, deer, and moose populations2. The return of the wolf restored a natural complement of predators to northwest Wyoming and returned the coyote to its role as a mid-level predator. Wolves will kill coyotes and outcompete them at kill sites. Coyotes also prey heavily on pronghorn fawns. Since wolves returned to the landscape, pronghorn populations have increased in northern Yellowstone as a result of declining coyote populations and densities 1.
Wolves and Scavengers
Scavengers, such as ravens, eagles, and bears, also benefit heavily from the return of wolves. Wolf kills provide scavengers with an important source of protein, particularly in winter. Twelve species of scavengers are known to visit wolf kills in Yellowstone National Park 10. Ravens are especially attuned to wolves and may fly over wolf packs as they pursue prey, allowing them quick access to wolf kills. In turn, wolves may benefit from ravens by following them to carcasses that can feed both species8.
Prior to the reintroduction of wolves, scavengers were more dependent on animals that died due to harsh winters. Since snow is thawing earlier as a result of a warming climate, there are fewer winter kills available for scavengers. Wolf kills may help buffer the impacts of climate change for scavengers by providing them with a food source in the winter9.
The return of the wolf to Wyoming has had significant ecological benefits in a relatively short period of time. Ecological concerns contributed to the decision to return wolves and should play a role in how states manage this keystone species. Although it is easy to focus on the perceived negative impacts of wolves, it is important to recognize the actual benefits they provide to our ecosystem. By regulating wildlife herds and reducing the prevalence of diseases, revitalizing riparian areas, reducing coyote densities, providing food for scavengers, and indirectly improving conditions for a host of other species, wolves play an essential role in maintaining the ecological health and integrity of the landscape.
Footnotes to this article
- Berger, K.M., E.M. Gese and J. Berger. 2008. Indirect effects and traditional trophic cascades: A test involving wolves, coyotes, and pronghorns. Ecology 89:818-828.
- Berger, K.M. and E.M. Gese. 2007 Does interference competition with wolves limit the distribution and abundance of coyotes? Journal of Animal Ecology 76:1075-1085.
- Cooke, H.A. and S. Zack. 2008. Influence of beaver dam density on riparian areas and riparian birds in shrub steppe of Wyoming. Western North American Naturalist 68: 350-364.
- Halofsky, J.S., W.J. Ripple and R.L. Bestcha. 2008. Recoupling fire and aspen recruitment after wolf reintroduction in Yellowstone National Park, USA. Forest ecology and management 256(5):1004-1008.
- Mech L.D., D.W. Smith, K. M. Murphy, and D. R. MacNulty. 2001. Winter severity and wolf predation on a formerly wolf-free elk herd. Journal of Wildlife Management 65:998-10
- Ripple, W.J. and R.L. Bestcha. 2006. Linking wolves to willows via risk-sensitive foraging by ungulates in the northern Yellowstone ecosystem. Forest ecology and management 230(1-3):96-106.
- Smith, B.L. 2005. Disease and Winter Feeding of Elk and Bison: A Review and Recommendations Pertinent to the Jackson Bison and Elk Management Plan and Environmental Impact Statement.
- Stahler, D.R., B. Heinrich and D.W. Smith. 2002. Common ravens, Corvus corax, preferentially associate with grey wolves, Canis lupus, as a foraging strategy in winter. Animal Behaviour 64(2):283.
- Wilmers, C.C. and W.M. Getz . 2005. Gray wolves as climate change buffers in Yellowstone. PLoS Biology 3:571.
- Wilmers, C.C., D.R. Stahler, R.L. Crabtree, D.W. Smith and W.M. Getz. 2003. Resource dispersion and consumer dominance: scavenging at wolf- and hunter-killed carcasses in Greater Yellowstone, USA. Ecology Letters 6:996–10
© 2013 Sierra Club. All Rights Reserved.
I also came across another excellent article on wolf ecology, this one entitled Wolves As Engineers of Biodiversity, published by the California Wolf Center, which I won’t reprint but you can view by clicking here.