Bighorns Shun Desert Water Tanks

This has been an ongoing controversy as wildlife managers have built giant water tanks within wilderness, allegedly to help Kofa bighorn sheep.  Instead, the bighorns avoid the water tanks.

The Kofa National Wildlife Refuge has also been planning to kill Kofa mountain lions to decrease predation on the bighorn sheep.  It’s a classic example of managers doing everything in their power to manipulate the natural world for a single-species – and getting it wrong anyway.

Bighorns Shun Desert Water TanksPEER News Release 9/15/09

(Tucson, AZ) Remote cameras installed to detect bighorn sheep use at two controversial man-made water developments constructed in the Kofa Wilderness in 2007 suggest the tanks have completely failed to provide water for bighorns. The cameras, installed by the US Fish and Wildlife Service (USFWS) at the McPherson and Yaqui Tanks, captured photos of mule deer, hawks, doves, vultures, coyotes and bobcats, but not a single bighorn drinking from the tanks in the two years since their construction.

“Building these artificial water developments in an attempt to artificially inflate bighorn sheep numbers was contrary to preserving the area as wilderness,” stated George Nickas, Executive Director of Wilderness Watch. “We’ve felt all along that the project was wrong from both a legal and ecological standpoint. The camera data bear that out and they completely undermine the USFWS’ argument that the tanks are necessary in Wilderness.”






  1. hilljack Avatar

    At least after all the effort of installing these tanks some wildlife is using them. I don’t know what they look like but mabye constructing them to have a natural appearance would work better.

  2. Ryan Avatar


    I would have to disagree on you take that their doing things wrong, the tanks, while not directly benefitting bighorns, are benefitting other species. As a side note Cougar removal has helped in raising sheep populations in other populations. There are plenty of cougars, there are not plenty of desert sheep.

  3. Ray Avatar

    “It’s a classic example of managers doing everything in their power to manipulate the natural world for a single-species – and getting it wrong anyway.”

    Do you suggest they do nothing? I’m confused… desert bighorns are endangered, the gov’t attempts something to help them, it doesn’t work, so they never should have tried in the first place? I understand there are plenty of other factors that affect bighorn populationss besides water, but I don’t get what was wrong with this effort.

  4. Brian Ertz Avatar

    Ryan says :

    I would have to disagree on you take that their doing things wrong, the tanks, while not directly benefitting bighorns, are benefitting other species.

    yeah – like mule deer, which compete with bighorn for forage.

    maybe if we built the tanks in wilderness, then slaughtered out all of the mule dear – then the bighorn would use the tanks ?

  5. ProWolf in WY Avatar
    ProWolf in WY

    They say they are killing the cougars to protect the sheep. Why are they so interested in the sheep? The answer is hunting. While I am a hunter myself, I question whether removal of a predator is really the answer. Are they not also considering what the population of mule deer will do if they remove predators? I doubt there is much competition with mule deer and desert bighorns, but it can still have a negative effect ont he ecosystem with large deer populations.

  6. Ryan Avatar

    “yeah – like mule deer, which compete with bighorn for forage.”

    Not really as there populations overlap a bit, but are generally not concentrated in the same areas. Coyotes, rabbits, eagles, birds, and about many desert creatures benefit from the water.


    Desert bighorns populations are not in good shape, the amount of hunting allowed is pretty minimal. I would suffice to say that maybe 100 tags are issued for the whole nation for desert sheep. Cougar predation has been noted as a cause for certain species that are in perils lack of rebound. It was noted in Peninsular Big Hord sheep (endangered), the wood caribou of the serilkik (sp) mountains, and certain populations of california bighorn sheep.

  7. Ryan Avatar

    “Game and Fish Department biologists informed the
    commission at its Aug. 7 meeting that the monitoring
    of one radio-collared mountain lion revealed it had
    killed 14 bighorn sheep since February, an average
    of one bighorn sheep about every 10 days. At this rate, this one lion is on pace to kill an
    estimated 37 bighorn sheep annually.
    By comparison, the estimated annual yearling recruitment from the Kofa National Wildlife
    Refuge bighorn sheep herd is only 39 animals.”

    KOFA has held one of the last healthy populations of Bighorns and sheep from Kofa have been transplanted all acoss the west. Its a very important population and protecting it is of the utmost importance.

  8. Ralph Maughan Avatar


    I agree that there may be a serious cougar problem here. Ecological changes have increased the number of cougar in an area where they once were rare.

    Draft EIS on the proposal to limit cougar on the Refuge:

  9. Ryan Avatar


    What from what I have read Cougar populations in the desert have been artifically high due to their predation on range livestock and wildhorse and burro foals, which is a good food source when their young, but they become challenging in size cougars revert to preying on Big Horns. Comments can be made about hunters, but less than .001% of hunters will ever get a chance to hunt any wild sheep in the lower 48 contigious states, or perhaps all of north america. The bighorn sheep is an Icon of the west and represents all that man has done both wrong and right with regards to destroying the populations.

  10. ProWolf in WY Avatar
    ProWolf in WY

    I would suffice to say that maybe 100 tags are issued for the whole nation for desert sheep.

    I didn’t know the population was that low.

  11. Ron Kearns Avatar
    Ron Kearns

    Brian Ertz,

    Thank you for posting this article. I have numerous comments to make about the Kofa NWR artificial water sources in wilderness and mountain lion issues, although I have been busy with interviews and with comments for the DEA Limiting Mountain Lion Predation on Desert Bighorn Sheep on the Kofa National Wildlife Refuge. I will try to respond by this weekend.

    There are issues of falsification of official documents by agency staff regarding these tanks and exaggerated and misleading claims regarding mountain lion predation rates.

    Ron Kearns
    Retired Kofa NWR Wildlife Biologist
    Former Federal Collateral Duty Refuge Law Enforcement Officer

  12. Ron Kearns Avatar
    Ron Kearns

    The following link has photos of wildlife *at* and some drinking from McPherson and Yaqui Tanks. The only bighorn camera-captured at either tank was not “using” the tank as the AGFD/FWS claimed. Logically, if an animal is “using” a water tank that would mean that he is drinking from the tank since the tank’s purpose is to provide drinking water for *use* by wildlife. The 1/2 bighorn photo frame only displays the south-end of a north-bound bighorn ram.

  13. Ralph Maughan Avatar

    Well then if bighorn don’t use the tanks, but mule deer do, the tanks might serve to increase the number of mule deer and so then the number of cougar. Is that right?

  14. Ron Kearns Avatar
    Ron Kearns


    Yes, that is one likely consequence, among others.

    One of the reasons I posted to your site is to garner opinions—such as yours—and perhaps add to the debate regarding artificial waterholes and mountain lion predation on desert bighorn.

    I have many opinions based on 25+ years working as a USFWS employee at Kofa NWR and from living in the area for 33 years. However, there is great value in hearing other opinions from all disciplines. Unbiased critical thinking and solutions to contentious issues often arise from people separated from the direct controversy where biases—assumed or blatantly demonstrated—are frequently intensified.

    Thank you for your comment.

  15. Ron Kearns Avatar
    Ron Kearns

    The link accesses an article with more detail about the 1 ram photo, the mule deer v. bighorn habitat question, and a different perspective on the ‘need’ for the $40,000 tanks (total cost).

    Arizona Daily Star Tucson, AZ


  16. Larry Thorngren Avatar

    As an infrequent visitor to KOFA over the past twenty years, I am curious about the lion that Ryan said killed 14 bighorns. Were the kills in rugged sheep habitat or were they kills of sheep that were lured to unsafe areas by the water tanks? The fact that the sheep are not using the tanks makes me think that they don’t feel safe enough to get a drink. Did cougars get every sheep that went for a drink?
    When I was photographing peninsular desert sheep at Borego Springs, CA, I saw desert sheep drinking from the small stream in Palm Canyon every day, but there were steep escape areas a few bounds away from the water.

  17. Ron Kearns Avatar
    Ron Kearns

    Larry T.

    A year ago and 3 months ago, PEER submitted a FOIA request for the map plotted GPS location data of lion-killed Kofa bighorn so we could determine if lions were using the waterholes at a ‘prey trap’. The FWS refused to give us that information because they said then (in June 2008) that this was just a Scoping process and that we could seek the information later during the Draft EA (DEA). PEER did not file an appeal because we thought that the DEA—since it took a year and over 1 month to complete—would have maps with GPS locations of where lions were snare-captured and where they killed prey—bighorn and mule deer primarily. The DEA has one general map of the refuge depicting the boundary, refuge roads, and surrounding highways!

    Therefore, I cannot say with any confidence where the lions killed bighorn. We all could determine that with locations plotted on a map with radii expanding out at various concentric distances from the waterholes as the focal points.

    This is what the FWS states in the DEA regarding locations relative to water sources. I would prefer to see the plotted data because the FWS/AGFD disingenuously omitted the plots of many water sources in the 2007 Investigative Report, so I do not trust the following data and it most likely underrepresents—or at least misrepresents—available water sources:

    “Data from the collared lions indicates that 28% of ungulate kills occurred within 1600 meters of a water source, while 20% occurred within 800 meters. Only 12% of ungulate kills occurred within 100
    meters of a water source (USFWS, unpubl. data).”

    Obviously, even 1600 meters (just less than 1 mile) is not a great distance for lions that have home ranges > 100 square miles. In addition, from aerial views of some Kofa waterholes, they appear as the hub of a wagon wheel with mule deer trails representing the spokes radiating from the hub. These well-travelled trails serve as conduits along which lions can ambush ungulates.

    However, to specifically answer your question, lions did not keep bighorn away from these 2 new water tanks because no lions were camera-captured in over 14, 952 hours that the camera was installed at new McPherson and no lion images were captured at Yaqui during a shorter period. Furthermore, there would have been evidence of lion-killed mule deer if lions were preying upon the numerous deer that were documented using these new tanks.

    The tanks were constructed in very good mule deer habitat and very poor bighorn habitat that is only used occasionally by rams and very rarely by ewes, lambs, yearlings, and young rams that might cross the valley in bands (groups) to move between ranges or ewes moving to lambing grounds. I have hiked and aerial surveyed the McPherson Valley extensively since 1978 and I have frequently observed mule deer but never any bighorn, whatsoever. That single frame capture of a bighorn ram corroborates my claim that this is not good bighorn habitat; even for rams that occasionally occupy the lower country during some seasons of the year.

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Brian Ertz