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Declining Deer Population: Blame It On The Mountain Lions

May 7, 2016
Clear Creek Canyon Deer. Notice how scrawny they are

Clear Creek Canyon Deer. Notice how scrawny they are


This is the time of year with Spring in full bloom that here in Colorado, we are likely to see more wildlife. It has been my good fortune to see a fair amount these past few weeks – beaver (which I had never seen until now), muskrat, avocets and then a few days ago a herd of seven mule deer grazing on the side of a slope above Clear Creek just beyond the entrance to Clear Creek Canyon. We had been hiking. Nancy went on a bit; as usual, I waited behind and took a seat on an inviting rock, looked up; there were all seven of them making their way down along a stream bed not far from me.

Alert, the deer were typically nervous, their ears going back and forth. Apparently deciding that in the end I was not much of a threat, they inched closer until they were no more than a hundred feet away, maybe closer. Common as deer are, it is still a great thrill for a kid (well, I’m 71 now) from Brooklyn to be in the presence of a deer herd wandering freely in the Colorado mountains. I don’t remember seeing them in Flatbush where I was born, not even in the wilds of Prospect Park.

Unlike the other wildlife described above, deer are quite common – not just in Colorado, but nationwide. It is not unusual to see small herds in the mountains either in the early morning or towards dusk. In some places, like Boulder, they are something between house pets and nuisances, enjoying garden produce sometimes more than the people who are raising the crops. On his farm in Lyons, I remember that my father-in-law would scare them away by firing blanks at them with is rifle. It worked pretty well for a short while and then they returned.

National Trends

Nationwide, the useful and informative website “Deer Friendly” provides a good deal of insights into both national and local trends.

2000-14 HarvestBoth here in Colorado and nationally deer populations are in decline – one might say plummeting. Nationally the trend is long-term. “Deer Friendly” reports that from 2000 to 2014 deer population have decreased from close to around 7,350,000 to 5,960,000, a drop of nearly 19%. It must be noted that these are approximate figures given that the ways in which deer are counted vary in different states, still the trend appears pretty clear: deer populations are dropping. These numbers fail to note that a hundred years ago, the deer population – like that of so much other wild life – was almost hunted to extinction. Looking at the figures over the longer term, this is quite a come back. So it would be more accurate to say, that there has been something of a deer revival which peaked – like the stock market – around 2000 and has been unstable ever since. (Wonder if there is some connection? – but for the sake of sanity – let’s not go there, at least not yet.)

Following the national trends, the Colorado deer population is also in decline these past 15 years. According to Colorado Parks and Wildlife (CPW), reported in The Denver Post, in August, 2014 “CPW’s most recent population estimates continue to show a significant statewide decline in mule deer, down by 36% to 390,000 in 2013 from 614,000 in 2005. The national decline of 19% noted above covers a 15 year period; Colorado’s mule deer decline of 36% is covering only an eight year period suggesting that deer populations in the state are dropping at nearly double the national average.

2016 - May 4 - Clear Creek - Near Golden - 23What’s the deal? Why the decline in the numbers?

Not to be cynical but, the big deal, frankly, is that hunting is a billion dollar business in Colorado and the concern over deer population decline involves hit on the state’s prosperity.

“Deer Friendly” cites three factors in the numbers’ shrinkage: “food supply, predation and energy development.” Explaining the decline at a 2014 conference made up mostly of Colorado mule deer hunters, Brad Weinmeister, a CPW biologist put it this way:

“We are all guilty of it [the decline in the deer population]. The last 20 to 20 years there has been a lot of growth in homes in th country with the new roads, driveways, dogs, horse pastures and traffic. It takes away from habitat and puts stress on the animal.”

While there is much truth in Weinmeister’s statement, it is a bit of a stretch to say that “we are all guilty.” Is that environmental version of the Calvinist idea that we’re all sinners? No we are not all guilty…and there are some well-known suspects in fact who are frankly far more guilty than others. Don’t blame the hunters either. Besides the fact that the numbers of hunters culling deer herds provide a necessary check on a deer population, deer hunters are, in their overwhelming majority quite sensitive to careful wildlife management – if only to maintain the sport they so love.

No, the decline has much more to do with the development epidemic that has touched every corner of the state and is most intensive in the mountains. Between ski centers, home building, the kind of mining that has eroded much land and poisoned no small amount of Colorado’s water supply, wild life have had a pretty hard time of it. Add to it now the fracking frenzy  and it is surprising that the deer decline isn’t greater. It was the combination of these factors, more commonly known as “development” are behind the wildlife decline not just in Colorado, but throughout the Western United States. And then there is Denver, deemed the fastest growing city in the United States today.  A recent U. S. Census Bureau report notes that 1000 new households a month are moving to Denver. 

A recent report by by the Center for American Progress and the nonprofit Conservation Science Partners details the loss of “natural land” (forests, wetlands, deserts, grassland) over the period 2001-2011 in eleven western states. It claims that every 2.5 minutes natural land “the size of football fields” is lost to development and urbanization. As an article in the Denver Post notes “a bear walking a random path couldn’t go farther than 3 1/2 miles on average before encountering ‘significant human development.’  In the decade studies, Colorado lost some 4321 square miles natural land, second only to California in the amount sacrificed to developers.

There is another factor at play – fracking. There are now estimates that Colorado now has more than 55,000 – you read that correctly – fracking wells. Their presence has greatly disturbed ecosystems and in different areas, the mountains included, water supplies. The relationship between fracking, disturbed ecosystems and the decline in the deer population has been noted by a number of environmental organizations that oppose the plans to kill mountain lions and black bear.

But, as Colorado is unlikely to do next to nothing (no – it will do nothing at all)  to put the brakes on Colorado’s development mania, state authorities have looked for another  explanation for mule deer decline and have come up with a somewhat less than brilliant solution to boost the deer herds: cut the mountain lion population! I guess it couldn’t be called “blaming the victim” but maybe it could be called “blaming the least guilty suspect.”

So mountain lions now are the fall guys for developers and real estate companies.

Last August, the Colorado Springs Gazette ran a story about how Colorado Parks and Wildlife hopes to increase deer populations in four nearby game management units as they are called north of the Arkansas River, between Salida and Canon City by allowing hunters to kill more mountain lions that pray on deer. It would permit hunters to increase the “mountain lion harvest” from a limit of 24 to 25 cats annually with a goal of doubling the area’s deer population.

The same article notes:

“The plan has drawn the ire of animal rights and conservation groups, who say that oil and gas development, habitat loss, disease and competition from elk and livestock are bigger threats to mule deer than any of their predators.”

As my daughter’s used to say when I’d say something either obvious or downright dumb…duhhhh!

USGS-map-of-CWD-distributionAnother factor is the prevalence of infectious brain disease, or chronic wasting disease as it is also called, that has been killing deer as well as elk and moose in Colorado – and in 22 other states and two Canadian provinces. Just how much chronic wasting disease has contributed to Colorado deer decline is difficult to ascertain, in part because the linkage between that cattle-infected and deer infected varieties while genetically very close is still open to question.

Nor have their been studies (to my knowledge) that would provide scientific evidence explaining the extent to which the disease is linked to population decline. Still it is striking that the parts of Colorado that have the most intensive number and size of cattle feedlots are also those in which the deer population have chronic wasting disease in epic proportions. So it can be said that cattle feedlots and mule deer chronic wasting disease seem to go together “like a horse and carriage.”And as the condition seems to have the ability to mutate and effect one species after another, the eerie possibility of some variation of chronic wasting disease “jumping” from deer and elk to their main predators in these parts – mountain lions. To date, there has been no evidence of such an outbreak among mountain lions, but it wouldn’t be a great surprise should it happen – if it hasn’t already. So Colorado mountain lions are getting it from both sides – from hunters and from the deer and elk they largely depend on for survival.

And as the condition seems to have the ability to mutate and effect one species after another, the eerie possibility of some variation of chronic wasting disease “jumping” from deer and elk to their main predators in these parts – mountain lions. To date, there has been no evidence of such an outbreak among mountain lions, but it wouldn’t be a great surprise should it happen – if it hasn’t already. So Colorado mountain lions are getting it from both sides – from hunters and from the deer and elk they largely depend on for survival.

The condition leads to “the characteristic spongy degeneration of the brain, leading to emaciation, abnormal behavior, loss of bodily functions and death. First identified in captive mule deer populations in a Colorado mule deer facility in 1967, the disease has reached endemic proportions in “a large swath of land in northeastern Colorado and southeastern Wyoming. First identified in captive mule deer populations in a Colorado mule deer facility in 1967, the disease has reached endemic proportions in “a large swath of land in northeastern Colorado and southeastern Wyoming.” There was also a 2008 case of contaminated elk meat sold at a farmers’ market in Longmont, Colorado that was found to come from a captive elk population infected with chronic wasting disease. How long will it be before the first reports of mountain lions being stricken too?

Is it more than a coincidence that this condition is especially widespread in that part of Colorado – the northeast – also known for its large cattle ranches and feedlots? Closely related forms of the condition have jumped from cattle to humans through the food supply; could the condition not have also mutated to effect genetically related (to cattle) deer, elk and moose?

According to the Colorado Cattlemen’s Association, Colorado feeds more than 2.3 million cattle annually, raised on 11,600 farms and 206 feedlots. Of Colorado’s 35,600 farms in 2013, 56.1% raised livestock (cattle and sheep primarily). Livestock are slaughtered in 24 USDA approved slaughter lots. Cash receipts for Colorado livestock and products total more than $3.7 billion, of which more than 75 percent of cash receipts come from cattle and calves. It is shipped worldwide and has been since the 1870s when a cattle baron named John Wesley Iliff shipped tens of thousands of head of cattle to France during the 1870-1871 Franco-Prussian war. That is a prodigious amount of meat that is processed here, most of it on the state’s northeast quadrant where 150 years prior, the deer and the antelope played and buffalo roamed.

Chronic wasting disease that brings down deer, elk and moose is related to a group of fatal diseases referred to as “transmissible spongiform encephalopathy (TSE). The group includes “mad cow disease” (bovine spongiform encephalopathy, or BSE) in cattle, scrapie in sheep and variant Creutzfeldt-Jakob disease in human, which, according to the World Health Organization, has been “strongly linked” to eating beef products contaminated with central nervous system tissue, such as spinal cord and brain from cows infected with mad cow disease. For an excellent article on “Mad Cow Disease” – first cousin to chronic wasting disease among cattle, read this. It speaks more about the condition’s spread in California, but if anything, it describes the situation in Colorado eastern plain feedlots as well.


  1. I have seen one of these magnificent cats in my 47 years in the state; it was down by Crested Butte on a hike along what is called Cement Creek. It was walking along a ledge on the other side of the creek. I was with Nancy and daughter Molly, who was a baby, my sister and her then-husband, Hubby and their son, Benji. It walked parallel to us for about 20 feet and then, thankfully disappeared into the brush. No one else in the party saw it and when I told them that I did I am not certain that they believed me. I’ve also looked for them on several occasions in the mountains above Boulder but have never seen another.
  2. Also published at Counterpunch 
3 Comments leave one →
  1. Sarge Cheever permalink
    May 9, 2016 2:52 am

    Interesting. Dears and rabbits have proliferated in suburbs in the Northeast and there id often a fight a to whether they should be culled or not. Yet, about 1905 or so it was calculated that there were only 500,000 dealer left in the U.S. an that they were in danger of extinction. Or so I read some where. There was a conservation movement (Ted Roosevelt) and the deer population slowly grew until it grew quickly in the last few decades. Sarge

  2. May 9, 2016 7:13 am

    This from Doug Vaughan lifted from Facebook:

    Having grown up on venison in a family of hunters and fishermen, I’m now afraid to eat wild game, not just deer and elk but turkey, pheasant, duck. So many streams, fields and pastures (and golf courses in the case of Canada geese) on which they forage are severely polluted with pesticides. Not as bad as beef but there’s another link, the effect on the gene pool of ruminants (and us) from feeding on pesticide-laden corn. On the drive back from Pennsylvania, where chronic wasting is epidemic among deer near farms, I ran out of gas and coasted downhill from I-76 exit to the town of Iliff, speak of another devil, through a miasma of cowshit and piss from feedlots along the Platte. An unemployed art teacher fighting for disability with rare hemacomatosis, running the only ramshackle store (liquor, smokes, an AR-14 propped in the corner), gave me a ride to Sterling for gas. Lanky teen cuhboyz and tight-jeaned bighatted cuhgirlz from Laramie’s show-horse team stopped to buy jerky from the only black kid in town, Marq, behind the counter at Conoco. Everyone worried about the prison shutting down for lack of inmates, the frackers cutting and running, with gasoline back up to $2.40/gal at Conoco, corn down, too. Nobody notices the stench of death hanging over the town. In Greeley they used to gleefully proclaim, “Smells like money!!”

  3. Robin Gaura permalink
    May 17, 2016 5:54 am

    Another possible factor in the decline in population of ruminants in the west could be the massive spraying of Roundup, or other glyphosate based herbicides on public lands and riversides. There is no way to find out how much is being sprayed, as no one keeps track of it. Glyphosate has devastating impacts upon gut biota of mammals, as well as acting as a broad spectrum antibiotic and chelator, among other health effects. In its role as a chelator, it strips soils and bodies living beings of manganese, zinc, and other essential minerals. The consequent mineral deficiencies are implicated in many degenerative diseases.
    One wildlife biologist has found several species of bird in Montana have gone extinct, due to developing an undershot beak, due to zinc deficiency. With the longer lower beak they cannot access their foods and die young. The same appears to be true with elk, as they are born with a longer lower jaw, which prevents successful nursing and access to foods. They die within the first year of life.
    I can´t remember the biologist´s name, I think I found her studies through Tony Mitra, on youtube. Other important information on the human consequences of glyphosate+adjutant mixtures on human food supply can be found at Dr Stephanie Seneff´s website at MIT, Dr Theirry Vrain, Dr Don Huber. There are many you tube lectures to support the science. This is a health disaster of epic proportions, affecting all creatures, not only humans. In 2013, the amount of glyphosate allowed in foods was increased massively by legislation that not one citizen group asked for.
    I have lived near mountain lions in both CA and AZ. When we last lived in the US, in the foothills of the white mountains, someone was dumping lots of the cats in the BLM lands around us, then hunting them. I knew of 6 mountain lions killed near our ranch by local ranchers, for sport. Lots goes on in the wilds that the `law´never knows about. It really is the wild west. The cats need a 200 mile range, and so are vulnerable as they traverse their area, at some point or other.

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