Amid controversy, gray wolves (Canis lupus) were reintroduced to Yellowstone National Park in 1995. Now, new studies are hinting at the added benefits that the once-spurned carnivore have rapidly brought to the preserve.
Research published last month revealed that—unlike other top predators—Yellowstone’s wolves routinely leave unfinished elk (Cervas elephas) and moose (Alces alces) carcasses. These provide essential scraps for scavenging coyotes (Canis latrans), eagles, and other animals. Related work suggests that these carcasses provide dinner more consistently, and for more species, than remains discarded by human hunters.
Other recently published findings show that wolves may also be rebalancing Yellowstone’s ecosystems. Some streamside trees, such as species of cottonwood (Populus) and willow (Salix) are growing vigorously once more in areas overgrazed for much of the last century, researchers wrote.
“Part of the integrity of the ecosystem has been restored,” said Christopher Wilmers, an ecologist of the University of California, Berkeley, and lead author of two of the studies. The findings vindicate the decision to bring wolves back, he said.
Wolves were systematically hunted in Yellowstone and much of the Western United States from the 1800s onwards. Yellowstone’s last pack was eliminated in 1926.
“In the early 1900s no one stopped to consider the ecological role of wolves,” commented Robert Beschta, a forestry scientist at Oregon State University in Corvallis. “Wolves were considered a predator with no value and seen as a huge constraint on allowing a productive ecosystem to flourish,” he said. Wolves, mountain lions (Puma concolor), and coyotes (Canis latrans) were all targeted as threats to livestock and game, he said.
When the National Park Service first considered reintroducing wolves in the late 1980s, critics warned that the predators might seriously impact elk, deer, and moose herds. Nevertheless, 31 wolves were re-introduced in 1995 and 1996 to Yellowstone, which spans portions of Idaho, Montana, and Wyoming. That population, now living in the vast park and its surroundings, had swelled to 220 animals in 21 packs by the end of 2001.
While elk numbers have been reduced by around 18 percent since the mid-1990s, few devastating impacts associated with the reintroduction program have yet been recorded, said Wilmers.
Feeding the Masses
Instead, the park is now enjoying some wolf-related benefits. According to Wilmers and colleagues’ study, published in the November Journal of Animal Ecology,wolves may be providing other scavengers with more regular meals than they’ve had since the early 20th century.
Mountain lions and grizzly bears (Ursus arctos) have a habit of sticking close by their kills, even when full. Wolves, on the other hand, tend to move away to “sleep off their meal,” said Wilmers, making meat available for scavengers.