Too Many Deer on the Road? Let Cougars Return, Study Says

Too Many Deer on the Road? Let Cougars Return, Study Says

Predator removals are the most unnatural of all our wildlife “management” perversions.

Restoring predators is the cheapest and quickest way to deal with excess deer and feral pigs, thereby rebalancing wildlife populations. Predators also do the best job of removing sick animals, protecting healthy deer, elk and bighorn from animal epidemics including sheep pneumonia and CWD.


NOTE: post originally appeared on on July 18, 2016


Cougars can kill hundreds of deer over the course of their lives, leading some scientists to argue that restoring them to 19 states with large deer populations could prevent automobile-deer collisions.


What large mammal regularly kills humans in the Eastern United States?

And what other large mammal might significantly reduce those deaths?

The answer to the first question is the white-tailed deer. Deer do not set out to murder people, as far as anyone knows, but they do jump out in front of vehicles so often that they cause more than a million collisions a year, resulting in more than 200 deaths.

The answer to the second question, according to a new scientific study, is the cougar.

Laura R. Prugh, a wildlife scientist at the University of Washington; Sophie L. Gilbert, a wildlife ecologist at the University of Idaho; and several colleagues argue in the journal Conservation Letters that if eastern cougars returned to their historic range, they could prevent 155 human deaths and 21,400 human injuries, and save $2.3 billion, over the course of 30 years.

And although cougars do kill humans sometimes, the scientists estimated that the total number of lives lost would be fewer than 30, far fewer than the number of lives saved.

The scientists studied 19 states, including Maine, Missouri, Ohio, South Carolina and Wisconsin. Four other states — Delaware, Illinois, Maryland and Rhode Island — were part of the eastern cougar’s historic range, which was wiped out by the early 1900s. However, those states do not have enough open forestland to support viable cougar populations, the scientists said.

I have a personal interest in this new report. In 2004, I wrote an entirely selfish and completely undocumented essay lamenting the damage that deer were doing to my garden and suggesting, only partly tongue-in-cheek, that the lawn and garden community would be willing to sacrifice a few pets and joggers if mountain lions could be brought to the suburbs to get rid of the Bambi plague.

I noted that deer were also responsible for human deaths, although that was not my true motivation.

I’m sure I wasn’t the first to have this idea. What deer do to cultivated suburban yards can make otherwise peaceful people quite bloody minded.

But I didn’t do the numbers.

Dr. Prugh and her colleagues have done the numbers in an attempt to find some real answers.

The return of cougars on their own is entirely possible, they say. The animals have come back to parts of the Midwest over the past few decades and are starting to appear in the East. One animal was documented in Connecticut. That kind of natural repopulation would be likely to face less resistance than a human-engineered reintroduction, which she was not advocating, Dr. Prugh said.

But would their reappearance really help?

She and her colleagues took a methodical approach to putting together available numbers on how deer populations grow, how many car accidents involve deer and how accidents increase with a growing deer population. They gathered information on how many deer a cougar might kill — about 259 over an average life span of about six years — and how much open, forested land was necessary for cougars to sustain a wild population — about 850 square miles.

Then the scientists tested a variety of mathematical models and came up with their projections. One of the questions they needed to consider was whether the cougars would be killing just deer that would die anyway from starvation or illness.

The scientists took what Dr. Prugh said was a conservative approach that about 75 percent of the deer the cougars killed would have died anyway. They also considered that as adult deer decrease in number, more fawns survive. So killing deer doesn’t immediately shrink the population.

Adrian Treves, the head of the Carnivore Coexistence Lab at the University of Wisconsin, Madison, who was not involved with the study, said he was impressed with the analysis and thought it might underestimate the benefits of cougars. He said in an email that there would probably be an even greater reduction in deer-vehicle collisions, “if governments and private citizens allow cougars to recover to historic levels.”

Figuring out the downsides of having cougars back was more difficult. The numbers of cougars would be considerable in some states once the deer and cougar populations stabilized — about 1,000 each in New York and Wisconsin, 350 or so in Missouri and only eight to 15 in New Jersey. They estimated lost livestock values in the areas studied at $2.35 million a year. But they were not able to get good estimates of pet loss, because it is hard to pin down which pets that disappear were killed by cougars. They may have been killed by coyotes, or cars, or may have been taken in by someone else.

Also, they could not account for the obvious emotional response to predators. Even if the estimate is correct that five times as many people would be saved by cougars as would be killed, death by deer and cougar are different.

“The idea of being killed in a car crash with a deer just doesn’t scare people the way the idea of a cougar leaping on your back in the woods does,” Dr. Prugh said.

But she says she hopes that if cougars do return to the Eastern states, an understanding that they could bring tangible benefits will make people “a little more accepting, even if they are still scared.”


The little Mexican Wolf would be a physiologically beneficial addition to far-West Texas wildlife.

Ranching, wildlife management, finance, oil & gas, real estate development and management.
  • “. . . the little Mexican Wolf would be a physiologically beneficial addition to far-West Texas wildlife . . .”

    I cannot think of one far West Texas rancher who would agree with that statement.

    If you’re interested in the truth about wolves, here are two books that have it.

    The Real Wolf by Ted Lyon and Will Graves with contributions by additional researchers and experts on the animal.

    Wolves in Russia by Will Graves

    • Dear Russ,

      I want to begin by thanking you for taking the time and trouble to read my remarks and to respond to them.

      Russ, I am a rancher in far-West Texas.

      The book which you have referenced represents the historic attitude towards wolves, and the principal thinker is Valerius Geist. He is an outspoken deer expert, a most engaging gentleman who was very helpful to us when we wrote our elk study. Dr. Geist authored at least one very good paper, discussing the problems that timber wolves have posed for unarmed human populations in places like Russia during World War II. He is speaking of those huge timber wolves. The societies were characterized by small isolated populations; and the worst dangers as I recall were in Stalinist Siberia. There, the Communist Party (like the Czarists before them) did not allow the citizenry to arm itself for all the obvious reasons.

      Even the biggest, most dangerous predators are discouraged by hunting. I’ve spent considerable time fishing in Alaska. I can tell you that where wolves are hunted they are very wary of humans. Same story with bear: In the Kamchatka Peninsula in the Russian far-East, if you spot a grizzly bear you only see his rear end because he is running: this is because these animals are hunted. Those animals in Yellowstone Park are never hunted: They may try to eat you.

      Of course nobody wants 200+ pound wolves roaming around populations that have no way of defending themselves. But, you are comparing apples and oranges.The Mexican Wolf is not even as large as a big labrador: They will not be a danger to humans, and if you run your cattle correctly they will not be a danger to them either.

      Wolves are an apex predator and as such they are essential to the health of the grass that your cattle eat. Please watch for my next post “The Serengeti Rules” which deals with this issue. Suffice it to say that every system requires the keystone species, a large grazer moving around, plus lots of prey species, plus lots of predators. Pull any of these elements out and the system goes into decline: that is why our far-West Texas ranges can support about 10% of the animal numbers that were run in the 1880s.

      I don’t know if wildlife populations matter to you, but, I read the other day that out West, where wolves were reintroduced coyote numbers dropped (wolves kill coyotes) and pronghorn fawn survival increased 400%. That sounds right and as the benefit works through the system, it will turn out that there would also be lots of increased grass for cattle. As far as their role in the system, cattle are the proxy for the bison that would be there but for humans.

      This furor about a small wolf which will never number more than 100-200 in far-West Texas shows that we ranchers are as big a problem for wildlife as any government agency. Last night I got in a friendly debate with a wildlife advocate who wants all the ranchers removed from public lands so that the wolves can make a come back. The irony is that conservationists like him, and ranchers like you are in fundamental agreement about your desired outcomes, and improved range conditions for cattle cannot be achieved without improving conditions for wildlife and that can’t happen without improving conditions for cattle, and predators. We’re all in one boat Russ: Both sides must rethink their basic suppositions, which is to say stop killing one group of animals to “help” a favored group, thereby inadvertently harming everything!

      Having said that, I thank you very much again for taking the trouble to express your thoughts on wolves.


      Chris Gill

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