Dr. Mark Elbroch, lead scientist of Panthera’s Puma Program, has recently published a critical blog post. In it, he explores the multiple factors that are driving the decline of pumas (Puma concolor, mountain lions, cougars, etc.) near Yellowstone National Park.
Following a fourteen-year study, Dr. Elbroch and his colleagues found that the puma population directly to the north of Jackson, Wyoming dropped by 48% between the years of 2002-2015. The reasons for this stark decline are, as usual, driven by humans.
In the years 1995 and 1996, wolves (Canis lupus) were reintroduced to Yellowstone. This was huge. The return of the ecosystem’s top predator had many positive effects, including a rebound in beaver numbers. This, in turn, strengthened Yellowstone’s wetlands. However, wolves have made life harder for the region’s pumas.
For one thing, wolves occasionally push pumas off kills; forcing them to work harder to get enough food to survive. In addition, wolves are a major cause of kitten mortality. Dr. Elbroch’s post mentions that at least 18% of all the kittens the scientists monitored were killed by wolves.
Then there is the matter of the elk cull.
Elk are the primary prey items for mountain lions near Jackson. But in the year 2000, federal and state wildlife agencies decided that the Jackson elk herd’s numbers needed to be thinned from 16,000 to 11,000 individuals. They also wanted to encourage the elk to space themselves more widely in the landscape, instead of congregating in the National Elk Refuge during the winter.
To accomplish these objectives, game agencies instituted what Dr. Elbroch described as, “‘liberal’ hunting measures” (Elbroch, 2018). I am assuming this means they eased hunting regulations. This move, along with the return of wolves, did lead to a significant reduction in elk numbers.
Unfortunately, elk now keep to the National Elk Refuge even more strongly than they did before. Pumas cannot compete with wolves in the open terrain of the refuge, and so stay in rockier and more densely forested habitats. There are now 70% fewer elk available to pumas during the winter. Consequently, Dr. Elbroch and his team witnessed many pumas starving to death.
Lastly, in 2007 the Wyoming Game and Fish Department decided to target pumas with increased sport hunting. They apparently wanted to reduce the risks to humans and livestock associated with the cats’ presence.
Heightened levels of sport hunting, competition with wolves, and a 70% reduction in the availability of elk had the unsurprising effect of causing great harm to Jackson’s puma population.
To help recover the region’s pumas, Dr. Elbroch and his colleagues recommend greater efforts to redistribute the Jackson elk herd. Furthermore, they advocate for dialing back puma hunting in areas that are inhabited by wolves.
In recent years, multiple studies have found that high levels of sport hunting can increase human-puma conflicts. This casts significant doubt on the notion that more sport hunting is good for pumas, livestock, or people. As Dr. Elbroch points out, ecosystems also need to be managed as unified wholes: not isolated segments.