Because most previous research has focused on population numbers, studying wolves at the pack level is critical.
This study looked at the effects of human-caused mortality on wolf pack social dynamics, taking a novel approach to analyzing species impacts based on group structure.
Humans impact wolf packs in national parks
JEAN-CHRISTOPHE VERHAEGEN/AFP via Getty Images
The study, which was published today in Frontiers in Ecology and the Environment, was led by Kira Cassidy, a research associate at Yellowstone National Park, and included co-authors from five national parks as well as University of Minnesota Voyageurs Wolf Project researchers Thomas Gable, Joseph Bump, and Austin Homkes.
"We wanted to focus on the impacts of human-caused mortality to the pack, a finer-scale measure than population size or growth rate," Cassidy explained, as per ScienceDaily.
They've discovered that the likelihood of a pack persisting and reproducing decreases as human-caused mortalities increase.
While many studies have looked at how humans affect wolf populations, this study took a different approach and looked at how human-caused mortality affects individual wolf packs.
Cassidy and her colleagues compared what happened to wolf packs after at least one pack member died from human causes to packs where no members died from human causes.
When a pack member died of human causes, the researchers discovered that the likelihood of the pack remaining together until the end of the year decreased by 27%, and the likelihood of the pack reproducing the following year decreased by 22%.
When a pack leader died, the chances of the pack surviving until the end of the year dropped by 73% and reproduction dropped by 49%.
Although the researchers did not investigate whether human-caused mortality affects the size of wolf populations in national parks, this study demonstrated that humans are clearly altering certain aspects of wolf ecology in national parks, even if they do not affect overall population size.
Humans are a disproportionate cause of mortality for wolves that live primarily in national parks, which is one reason for this.
In other words, wolves die from human causes more frequently than would be expected given the amount of time they spend outside of park boundaries.
The wolves in Voyageurs National Park spent the most time outside of the park boundaries of any national park studied.
Wolves with territories in or overlapping with Voyageurs spent 46% of their time outside the park.
As a result, people were responsible for 50% of these wolves' deaths, with poaching being the most common cause of death.
Human-caused mortality accounted for 36% of collared wolf mortality in all five parks studied, including Denali National Park and Preserve, Yellowstone National Park, Grand Teton National Park, and Yukon-Charley Rivers National Preserve, with human-caused mortality accounting for 36% of collared wolf mortality in all five parks.
During hunting and trapping seasons, legal hunting and trapping of wolves outside of national park boundaries accounted for 53% of all human-caused mortality for wolves from national parks.
These findings highlight the importance of collaboration between various state and federal agencies in conserving and managing wildlife that enters and exits protected areas such as national parks.
Although wolf packs once roamed from the Arctic tundra to Mexico, habitat loss and extermination programs resulted in their extinction across the majority of the United States by the early 1900s. In 1973, the United States, as per the National Park Service.
The Fish and Wildlife Service (FWS) designated the Greater Yellowstone Ecosystem (GYE) as one of three recovery areas for the northern Rocky Mountain wolf (Canis lupus).
41 wild wolves from Canada and northwest Montana were released in Yellowstone from 1995 to 1997.
Wolves from the expanding population, as expected, dispersed to establish territories outside the park, where they are less protected from human-caused mortalities.
The park contributes to the species' long-term viability in GYE by providing a location for research on how wolves may affect various aspects of the ecosystem.
The 25th anniversary of wolves returning to Yellowstone was on January 12, 2020.
Wolves eat a wide range of prey, both large and small. They effectively hunt large prey that other predators are unable to kill.
In Yellowstone, elk account for 90% of their winter prey, and deer account for 10-15% of their summer prey. They also slaughter bison.
Wolf kills benefit many other animals. When wolves kill an elk, ravens, and magpies appear almost immediately.
Soon after, coyotes appear and wait nearby until the wolves are satisfied. Bears will usually be successful in chasing the wolves away.
Many other animals, ranging from eagles to invertebrates, consume the carcasses.
