The Gray Wolf: An Apex Predator Story

The gray wolf’s (Canis Lupus) story is a fascinating account of species near-extinction and comeback in the American west. Here, we will look at some specifics about the gray wolf, what an apex predator is, the gray wolf’s re-introduction into the northern Rocky Mountains and why the wolf and apex predators in general are vital players in a healthy ecosystem. We’ll also introduce the idea of using both Scientific Ecological Knowledge (SEK) and Traditional Ecological Knowledge (TEK) as a means of restoring an ecosystem.

DEFINITIONS

• Apex Predator: The top predator in a food web, without any natural predators.
• Mesopredator: A mid-ranking predator in a food web.
• SEK (Scientific Ecological Knowledge): Scientific knowledge generated through a strict and universally accepted set of rules formed by academic disciplines (ecology, biology, forestry, etc). Addresses the return of an ecosystem to a close approximation of its condition prior to disturbance. In restoration, ecological damage is repaired; both the structure and the function of the ecosystem are recreated. Time frame is in decades.
• TEK (Traditional Ecological Knowledge): Describes indigenous or other traditional knowledge of local resources handed down through generations generally through traditional songs, stories, and beliefs. It includes the restoration of relationship to land, based on respect and reciprocity for the gifts we receive from the land. A partnership with dynamic natural processes. Time frame is in generations.
• Reference Ecosystem: A community of organisms that serve as a model or benchmark for restoration following a disturbance by human activities such as agriculture, logging, development, fire suppression, or non-native species invasion.

Wolves are the wild ancestor of all domesticated dogs. Their body size varies from three to five feet long with a tail of one to two feet long. Females weigh from 60 to 100 pounds and males range from 70 to 145 pounds. Their average lifespan is 8 to 13 years. They are carnivores that prefer large hoofed mammals but will also eat smaller mammals, generally eating every 5 – 7 days. Wolves live in packs of 2 – 15 members but can increase up to 30 members before some individuals break off to find new territory. There are both male and female hierarchies in the pack; the alpha male is dominant over the entire pack and only the alpha male and alpha female breed. Breeding occurs from late January through March, gestation is about 63 days, and there are typically 4 to 6 pups in a liter. Wolves communicate through body language, much in the same way our domesticated dogs do. Howling is used for long-distance communication to pull a pack together.

The wolf was once widespread across most of North American but it was hunted to near extinction in the early 1900’s. Today the North American Gray Wolf ranges across the Northern Rockies, the Pacific Northwest, the Western Great Lakes Region, from the US/Canada border into the Arctic (including Alaska and Greenland), in a small region along the
Arizona/New Mexico border, and a few struggling to survive in Mexico. In the 1800’s, Yellowstone National Park was once home to several large predators including grizzly bears, black bears, wolves, and mountain lions along with a robust population of bison, elk, mule deer, pronghorn, and bighorn sheep. The last Yellowstone wolf pack was killed by humans in 1926. With the wolves gone, the bear and lion populations greatly diminished and the elk populations skyrocketed. Elk populations continued a boom and bust cycle due to targeted killing as well as fluctuation due to climate variability. Fast forward to 1995 when, in an effort by the federal government to remove the gray wolf from the endangered species list, 41 gray wolves were reintroduced into Yellowstone National Park and additional wolves were reintroduced into Idaho. Some people were concerned that this reintroduction would wipe out the elk populations. However 25 years of study has shown that the wolves prey on the weaker, undernourished, bull elk and older cow elk which has helped to create a much more resilient and balanced elk population. The wolves also prey on elk calves, however this has not led to an overall reduction in survival of elk calves. In Idaho, state pushback to the wolf reintroduction program led to turning over the management of the project to the Nez Perce Indian tribe who viewed the wolf recovery efforts as linked to the recovery of their tribe as well. The tribe was eager to restore the biodiversity and ecological balance of the northern Rocky Mountain ecosystem. Like many Native Americans, the Nez Perce have a special affinity with the wolf, and share a similar history of persecution and being forced onto ever-smaller habitats. Restoring the gray wolf to its historic range allowed the tribe to reestablish its cultural ties to the wolf. Importantly, the gray wolf recovery effort marked the first time a native tribe was able to take the lead role in reintroduction of an endangered species.

Wolves fill a unique role in an ecosystem both as an apex predator and a keystone species. Recall from the previous post (The Oregon Alligator Lizard and his Food Web) that a keystone species plays a critical role in a food web. If a keystone species is removed from a food web, the ecosystem would change dramatically. An apex predator is at the top of the food web of a given ecosystem (“top dog” in this case), and also has a profound effect on the functioning of the ecosystem. Wolves help restore stability to their ecosystem by providing scavenging opportunities for other animals and improving riparian areas by hunting herbivores. In Yellowstone, for example, the reintroduction of wolves forced elk to stay on the move, freeing sensitive riparian areas from overgrazing and allowing vegetation to recover along streams. More willows and aspen trees provide food and habitat for beavers. Beaver ponds benefit aquatic habitats in several ways including allowing trees to provide shade to cool the water and improve habitat for fish. Wolves also help to control the coyote (a mesopredator) populations, which in turn allows the rodent populations to increase and provide food for struggling birds of prey. The remains of a carcass left behind by wolves help feed grizzly bears, bald eagles, wolverines, and other scavengers.

Apex predators influence ecosystems in several important ways including limiting the number of prey in a habitat (i.e. elk in Yellowstone) and thereby controlling smaller mesopredators. Without apex predators, a habitat experiences an outbreak of mesopredators which leads to diminished biodiversity. Studies have shown that apex predator populations are self-regulated. Whereas small carnivores share fast reproduction rates and have higher densities, large carnivores (like wolves) have a slow reproduction rate, extended parental care, sparsely populated territories, reproductive suppression, shared parental care, and cooperative hunting. This self-regulation may ensure that the largest and fiercest do not overexploit their resources.

MAKING THE CONNECTION

In my last post I introduced the concept of a food web and how the interconnectedness of species within a given food web is vital to a healthy ecosystem. Here I’ve tried to hone in on the importance of apex predators in food webs. This is an important concept to understand since many of our apex predators are viewed by humans as threatening and in need of “control” or extermination. Wolf restoration programs are generally viewed as positive by people that have the least experience with them and negative by people who live in areas where wolves reside and sometimes prey on livestock. In North America, livestock does not make up a major portion of wolf prey. Furthermore, wolves do not automatically hunt livestock, although they may learn to kill them at some point. Confirmed wolf depredations make up a comparatively small portion of all livestock losses. If livestock owners engage with wildlife management agencies to address concerns about predation, the tensions that exist between these groups can be reduced. Yellowstone National Park is actually a rare place where wolves are completely protected. The reintroduction and monitoring of the wolf packs of Yellowstone has provided a unique opportunity for people to understand the true nature of these animals. We are able to see that they are subtly restructuring the ecosystem.

Robin Wall Kimmerer guides us to think about ecological restoration of our land through two lenses: SEK and TEK or indigenous ways of knowing + western scientific knowledge. She explains that it is not only the land that is broken, but our relationship to the land that is in need of repair. TEK is an important overlooked resource in ecological restoration. Reference ecosystems can be identified using SEK however with TEK, information on a reference ecosystem relies upon oral history, ethnographies (the customs and cultures of a group of people), harvest practices, management practices, and material culture. Incorporation of TEK allows movement from simply ecological restoration to biocultural restoration. Kimmerer explains that “biocultural restoration is an approach to healing damaged lands and to healing relationship between people and place with the aim of generating a mutually sustaining, life-renewing landscape which supports the livelihoods of both human and more than human beings who are dependent on that landscape.” This practice draws on multiple ways of knowing. It leads to reciprocal restoration, where restoration of land and ecosystems contribute to cultural revitalization and, in turn, this renewal of culture promotes restoration of ecological integrity. I encourage you to listen to Kimmerer speak more fully on this topic (see reference #9).

ADDENDUM

I mentioned above that when the gray wolf population was absent in Yellowstone National Park the bear and mountain lion populations decreased. I’d like to provide some further research and discussion on why this would happen.

Let’s first look at the wolf – bear interactions. Grizzly bears, black bears, and gray wolves have historically shared habitat throughout their range in North America. These interactions revolve around food sources and are characterized as “mutual avoidance”. Wolves may occasionally kill weak or young bear and bear have been noted to occasionally kill wolves, but these interactions are rare; most interactions between the two species are stand-offs as they defend their young or food source. Wolves prey on ungulates year-round whereas bear feed on ungulates primarily as winter-killed carcasses (after emerging from their dens) or ungulate calves in the spring. Bear mainly feed on grasses, sedges, forbs (flowering plant), berries, nuts, and roots. In YNP, most early-winter wolf-killed carcasses are consumed by coyotes before bears emerge from their dens. It has been suggested that bears benefit from wolf presence in the park because wolves prey on ungulates year-round and since bears readily displace wolves from their kill, this allows a more reliable food source for the bear for a larger portion of the year.

Now let’s look further at wolf – mountain lion interactions. A recent study showed that where these two species overlap in an ecosystem, wolves cause a decrease in mountain lion numbers by starving out adults and killing their kittens. When wolves are absent in a habitat, elk herds spread out and reside in relative comfort in mountains. However when wolves are present, elk herds congregate in larger groups in open grasslands to protect themselves from a wolf pack attack. Since mountain lions stalk and ambush their prey under cover of brush, they are less effective in hunting in the grasslands and starvation becomes an issue for the cats. Recent studies show the effect of wolf populations on mountain lions to be profound and much more impactful that human hunting of mountain lions.

It seems the earlier statement made about both bear and mountain lion populations decreasing when wolves are absent from an ecosystem may be outdated. More recent research that has been conducted since the wolf reintroduction into YNP seems to indicate that there is at least a benefit for bear to share habitat with wolves and a sort of equal standing between the two species allowing them to co-exist. However it seems clear that mountain lion populations definitely suffer a decline when sharing habitat with wolves.

I hope this discussion further illustrates the complex interactions between various species in an ecosystem and the delicate balance needed to maintain a healthy, functioning food web.

REFERENCES:

1. Kesselheim, A. The Howling Wilderness. January 2021. The Sun. Chapel Hill, NC.
2. https://www.nationalgeographic.com/animals/2020/07/yellowstone-wolves-reintroduction-helped-stabilize-ecosystem/
3. https://www.nationalgeographic.org/media/gray-wolf-educator-guide/?utm_source=BibblioRCM_Row
4. https://academic.oup.com/bioscience/article/53/4/330/250155
5. https://onlinelibrary.wiley.com/doi/abs/10.1111/oik.01977
6. https://www.nwf.org/Educational-Resources/Wildlife-Guide/Mammals/Gray-Wolf
7. https://digitalrepository.unm.edu/cgi/viewcontent.cgi?referer=https://search.yahoo.com/&httpsredir=1&article=1650&context=nrj
8. https://en.wikipedia.org/wiki/Apex_predator
9. https://www.youtube.com/watch?v=qioZC81b7WM
10. https://dfw.state.or.us/Wolves/docs/2019_Oregon_Wolf_Plan.pdf
11. https://www.nps.gov/yell/learn/nature/bearwolves.htm
12. https://www.smithsonianmag.com/science-nature/how-wolves-western-united-states-are-driving-down-mountain-lion-populations-180976775/