Last week, Drs. Mark Elbroch and Howard Quigley announced a “provocative” new paper (Elbroch, 2019). In it, they concluded that high levels of mountain lion (Puma concolor) hunting might harm mule deer (Odocoileus hemionus) populations in the American west.
This finding might seem counterintuitive, but it’s based on years of hard science.
Elbroch and Quigley, both of whom work for the wild cat conservation organization Panthera, recently completed a 4 and-a-half-year study called the Teton Cougar Project. During that time, Elbroch, Quigley, and a host of other researchers gathered obscene amounts of data on what mountain lions (AKA “pumas”) were eating near Jackson Hole, Wyoming.
Elbroch and his team attached GPS collars to 13 pumas, allowing them to monitor the cats’ movements. They visited 3,261 “clusters:” groups of GPS points that indicated the cats weren’t moving much, and possibly on a kill. In this way, the researchers recorded 1,398 puma kills (Elbroch & Quigley, 2019).
Elbroch & Co. then took all this data and subjected it to mathematics, revealing a compelling pattern.
The age of a puma strongly predicted its preferred prey. From ~12-20 months old, pumas typically hunted small animals like porcupines. The cats then began to target deer, and started incorporating elk (Cervis canadensis) into their diets around 40 months (3.3 years) of age. After that, the studied pumas increasingly specialized on elk as they grew older (Elbroch & Quigley, 2019).
This could have startling implications for puma hunting.
When people hunt pumas, they usually prefer the oldest and most impressive individuals. Thus, high levels of hunting could skew puma populations so that there’s an overabundance of younger cats on the landscape – who primarily eat deer.
Why does this matter?
Thanks to severe droughts and habitat loss, mule deer are declining in the Rocky Mountains (Koshmrl, 2019). People have long believed that killing pumas can bolster mule deer populations, even though this is not supported by science. Nevertheless, Colorado Parks and Wildlife recently launched a puma and bear cull to help mule deer, despite widespread opposition from scientists and the public.
Culls like those being practiced in Colorado might, paradoxically, harm the very species they’re meant to protect. However, Elbroch stressed that scientists need more evidence to know for sure if this is the case.
Elbroch and Quigley’s study is the latest in a long line of research claiming that too much puma hunting can have unintended consequences. For example, in this post I wrote about how excessive sport hunting can endanger humans and livestock by disrupting pumas’ social systems.
Given this growing body of evidence, wildlife agencies should exercise restraint in regard to puma hunting: their decisions need to be based on the best available science and the wishes of all their constituents, not just those of special interest groups.