In the year 2000 a group of scientists began monitoring 147 wild pumas across 2,300 square kilometers in the area of Yellowstone National Park in the state of Wyoming in the United States and carried on doing so for 17 years.
Over this period the population of pumas in the area fell by nearly a half, or 48% to be precise. The question the researchers wanted to find out why this happened. Was it human hunters or a lack of suitable prey? Or was it the presence of recently reintroduced gray wolves, which came to be competitors to local pumas as apex predators?
The answer, according to a newly published paper, is that the wolves have had an outsized influence on local pumas because they influence not only the big cats’ prey selection options and habitat use patterns (something that has already been known) but also inhibit their survival by reducing their reproductive rate while preying on puma kittens.
Although human hunters were found to contribute to a decline in puma numbers in the area, the impact was relatively low since “it was estimated that hunting in this particular system was equivalent to the effects of 20 wolves on puma abundance,” observes Panthera, a conservationist group dedicated to the protection of big cats worldwide, which sponsored the study.
“These results were surprising. While puma populations clearly mold themselves around wolves, no one would have predicted that wolves curb their numbers more than human hunting,” notes Mark Elbroch, the nonprofit’s director of its Puma Program. “The results should impact how we manage pumas in areas where the two carnivores coexist, including whether or not we allow them to be hunted.”
Gray wolves were driven extinct by people in Yellowstone National Park in the 1920s, which soon led to an ecological imbalance. Without a natural predator, local elk populations increased, which caused intense degradation in the area’s habitat. In 1995 wolves were reintroduced to Yellowstone by the US’s National Park Service to restore ecological health to landscapes under their management.
“A key cautionary takeaway for state wildlife agencies utilizing hunting as a management tool for pumas is that their populations can decline rapidly where wolves are recovering or being reintroduced,” Panthera said in a statement.
As rewilding efforts get underway in other areas, wildlife experts should assess the status of carnivores like pumas before reintroducing other top carnivores to avoid drastic population declines of the kind that has taken place in the Greater Yellowstone area’s ecosystem.
The findings also demonstrate “the interconnectedness of ecosystems and the need within the fields of conservation and wildlife management for a broader, multi-species strategy, as opposed to single species management,” Panthera stresses.
However, this does not mean that grey wolves should now be hunted again so as to improve the lot of pumas in the area, experts caution.
“In no way should these findings be misconstrued as a scientific endorsement of the hunting of gray wolves,” Howard Quigley, executive director of Panthera’s Conservation Science department.
“Instead, if we are to protect these apex carnivores whose survival is so critical to that of their ecosystems and surrounding human communities, the science clearly indicates that the way forward is to reduce or eliminate the hunting of pumas, or at least be very conservative where they share their homes with wolves,” Quigley says.
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