Could Mountain Lion Hunting Harm Mule Deer?

A mother mountain lion and her cub.
There may be a surprising link between mountain lion hunting and mule deer populations, and it’s not what you might think. Headrest by Valerie. CC BY-NC-ND 2.0

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.

See caption.
Some of the landscape near Jackson Hole, Wyoming. Jackson Hole, Wyoming by Maurizio Laudisa. CC BY-NC-SA 2.0

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.

A mule deer.
Wyoming Mule Deer by USFWS Mountain-Prairie. CC BY 2.0

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.

25 Thoughts

  1. I hope pumas to be saved and also the other wild animals too dear Josh, so sad to hear that hunting is still damage to the nature. Thank you, Love, nia

    Liked by 1 person

    1. Thanks Nia! In the US hunting isn’t the biggest threat to pumas, but in other parts of the world it’s a much more severe problem. Still, more and more studies are suggesting that too much puma hunting can have unintended consequences, which is why it’s still best for management agencies to use caution when making rules about puma hunting.

      Liked by 1 person

    1. Yes, Jess, part of the problem comes down to the way conservation is funded in the U.S. Hunting-related sales play a large role, so the interests of hunters often take precedence – even when they conflict with the wishes of most of the public. While hunters have done a lot of good for many species in the U.S. – and while regulated puma hunting is much better than an unregulated free-for-all – when it comes to predators like mountain lions there are still lots of biases that get in the way of sound management. That’s why research like Elbroch and Quigley’s that puts those biases to the test is so important.

      Liked by 1 person

  2. Hello Josh,
    As always, thank you for sharing such invaluable information in a way that is thought-provoking and accessible to all readers. For me, this also shows how “inter-connected” each part of nature is…it is not simply ‘pick and choose’ and no action is isolated.
    Wishing you a great week ahead!

    Liked by 2 people

    1. I had the same though as you: I had no idea that puma diets change with age, but now it makes sense – an elk would be hard to bring down for a young, less experienced cat!

      I’d assume that elk populations might grow with fewer mature, seasoned pumas on the landscape, but I don’t know for sure. I guess that’d depend on whether wolves start to focus more on elk due to less competition from pumas, and possibly other factors that I’m not aware of.


      1. Nice thought on the wolves. Then you have to think how different vegetation is affected by changing numbers of theses animals. This really shows just how much everything is connected in any given ecosystem. Nice write up!

        Liked by 2 people

  3. Crazy how killing amazing creatures actually have negative consequences on the environment, huh?! Makes me so sad to think people are willing to kill these cats that are just minding their damn business and living their lives the way they’re supposed to.

    Liked by 2 people

    1. We’ve known for a long time that removing too many top predators is bad for the environment, but some wildlife agencies seem slow to accept science. It is sad that agencies like Colorado Parks and Wildlife are culling these amazing cats, even though we know that they’re not to blame for the decline in mule deer numbers.

      Liked by 1 person

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