Impacts of Livestock on Southwestern Wildlife
Presented to Forest Service Training School
March 13, 1977
If there is one fact that wildlife people have succeeded in driving home in recent years it is the importance of habitat in maintaining wildlife populations. The fact that we've been more than moderately successful in this area is indicated by the tack being taken by the anti-hunting element. Hunting critics now accuse us of using habitat destruction as a red herring to cover up the fact that it is really hunting that is wiping out wildlife populations--including, I suppose, such avidly pursued big game species as the endangered Kirtland's warbler, Everglade kite, spotted bat, and long-toed salamander.
The blossoming interest in wildlife habitat preservation has resulted in increasing confrontations between conservation groups and those special interest groups more interested in greenbacks than in green belts. The consequences to wildlife habitat of river bottom clearing, stream channelization, or strip mining are readily demonstrated and concerned individuals and conservation organizations don't hesitate to express their opposition to such activities. When necessary they even take legal action to stop projects that will clearly destroy or degrade wildlife habitat. The problem of overgrazing impact on wildlife is more complex, however, and the damage to habitat is less easily demonstrated. But that does not mean that the long-term consequences of overgrazing are any less severe than those of various other insults to our environment.
Whenever I talk or write on this subject I invariably get accused of being anti-grazing, anti-cattleman, or anti-beef. I haven't yet been charged with being anti-American but it wouldn't surprise me. The fact of the matter is I like beef about as much as anyone and I'd be concerned about any move to deprive me of this form of protein. I am anti-land abuse in whatever shape or form it is manifested, including excessive grazing. I have tried to emphasize this point on other occasions but invariably my remarks are interpreted to be an indictment of the entire livestock industry. It simply isn't so and I want to again emphasize this point.
I am a firm believer in the wise use of all natural resources. I could no more object to converting range forage to beef than I could object to the hunting of deer and elk. But grazing, like hunting, should be geared to remove only the annual crop, to take the interest without dipping into the capital. Anything more is overgrazing and if it is carried on long enough will eventually reduce carrying capacity drastically for both livestock and wildlife--just as your capital account will be reduced by taking out more than the interest.
Moderate grazing can actually be beneficial to some forms of wildlife. Personally I'm inclined to believe that healthy wildlife populations should be nothing more than a by-product of sound range management programs. I am happy to support such programs. It is the all too prevalent abuse of our rangelands by too many head of livestock that concerns me.
National Forest lands in the Southwest are in far better condition than rangelands administered by other land management agencies. But, there is room for much improvement yet. Many of you would freely admit this, I'm sure. I'm not going to bore you with estimates of the percentage or acreage of National Forest lands classified as poor or worse. You should be more familiar with the data than I am, since they were taken from FS reports and publications. Suffice to say that many allotments are still seriously overgrazed and the USFS is nowhere near the point where it can rest on its laurels--particularly here in Arizona.
Some of you may well be wondering: Isn't it possible to go out on practically any range in the state and find song birds, small mammals, and, depending on vegetation type, quail, turkey, deer, elk or javelina? In view of this how can I stand up here and carry on about widespread overgrazing and its impact on wildlife habitat?
How indeed? The fact that such a thing is indeed possible is the reason why it is difficult to convince sportsmen and others with an interest in wildlife that overgrazing is truly damaging to wildlife populations. Bulldoze a stand of bottomland mesquite and the consequences are pretty dramatic: All the wildlife that once used that thicket disappear. The impacts of overgrazing, however, are more subtle. A species or population is seldom eliminated completely, although that too can happen, as the extirpation of the Masked Bobwhite will attest. But more typically, overgrazing acts to reduce the carrying capacity for indigenous wildlife.
Let's consider some representative Arizona wildlife species and review what we know or suspect of the impacts of overgrazing.
Gambel quail: Here is a species heavily dependent on the seeds produced by a variety of forbs that develop as a result of winter rains. No one to my knowledge has compared population levels under different intensities of grazing. It is possible at times to find considerable numbers of Gambel quail even in heavily grazed situations. Yet we know the bird requires good ground cover for nesting, and we know it is more vulnerable to predation by Cooper's hawks, its principal predator, when ground cover is scarce because of overgrazing. Further, when ground cover is scarce a covey is inclined to run ahead of a hunter instead of scattering and freezing as it would in good cover. This works to the advantage of the less-than-sporting hunter, willing to ground-sluice a covey. (I once had such a paragon of sportsmanship brag about getting 14 in one shot! And he probably crippled another half dozen or more in the process.) Paradoxically, behavior of this type under overgrazed conditions when ground cover is scarce frustrates the hunter who refuses to shoot a bird on the ground. He may wind up chasing the running quail until he is exhausted.
As for year-to-year quail population levels, we know that the Three Bar Wildlife Area, ungrazed since the early 1940's, is consistently one of the best quail areas in the state. The difference between quail populations on the Three Bar and on adjacent areas is particularly noticeable in years when the rains don't come and when cattle have been even more destructive of quail habitat than usual.
Extremely heavy grazing in the Oracle Junction area, not far from here, has severely damaged Gambel quail habitat and reduced its attractiveness to the hunter. It used to be my favorite quail area in the 1950's. I rarely even try hunting there anymore.
Scaled quail: Everything I said about Gambel quail is even more true for the scaled quail. This is more of a grassland species and is even more adversely affected by overgrazing as a result. The population of Oracle Junction is near the north end of its distribution. Habitat destruction by overgrazing during the past 25 years has about eliminated scaled quail from this area.
Mearns quail: The welfare of this species is absolutely dependent on tall perennial grass cover. This is especially necessary during the nesting season but it's also important as escape cover throughout the year. This is one species that's actually benefited by some grazing, yet excessive grazing will have severe impacts. Moderate grazing encourages the sedge and sorrel so vital as food sources for this bird but without the tall grass cover no amount of feed is going to prop up the population.
Whitetail deer: Tall grass cover seems to be nearly as important for the diminutive Coue's deer as for Mearns quail. The two species occupy the same habitat in Southern Arizona. Both seem to do best in moderately grazed or ungrazed situations. We don't understand why the Coue's deer favors good grass cover but it apparently does. Research data again is scarce because no one has investigated the issue. On the Three Bar area a chaparral watershed converted to grass was found to be far more heavily used by whitetails than adjacent brushy watersheds. Also on the Three Bar we have noticed increasing incursions of whitetails into lower elevations into what we would normally consider mule deer habitat. As mentioned before, the area has not been grazed in nearly 40 years and we believe the improving grass stands at the lower elevations are responsible for the downward movement of the whitetail. In other areas the converse has been observed: Whitetails retreating to higher elevations as the lower areas have been overgrazed.
Mule deer: There is probably more controversy over the effects of overgrazing on the mule deer than on any other species. I suspect the main reason for this is the oft told tale of the improvement in mule deer habitat that occurred 75-100 years ago when heavy livestock use drastically altered the character of historical mule deer habitat. As the perennial grasses were eliminated the shrubs increased in density and expanded into former grasslands.
As a result of this widely recognized fact--that overgrazing of the historical pristine conditions favored mule deer populations--we now have people, including some biologists, who believe that the overgrazing prevalent today is still beneficial to mule deer. This is nonsense, of course.
What is ignored in this scenario is the fact that once the virgin grasses were suppressed erosion followed. As soil erosion continued the density of desirable forbs, half shrubs, and shrubs decreased. What we have today in Arizona, in many areas that once supported luxuriant stands of grasses, is a gully-scarred landscape producing little more than worthless shrubs. Obviously such an end product of chronic overgrazing is not going to be in the best interest of mule deer populations--or of any other desirable species of animal life.
Unfortunately there have been no studies comparing heavily grazed and ungrazed areas which would demonstrate conclusively the impact of overgrazing on mule deer. On the Three Bar Wildlife Area again we have good deer population estimates but none for adjacent grazed areas. However, it has been obvious to the biologists working there that despite some ups and downs in numbers, mule deer numbers on the Three Bar have been significantly higher than on the adjacent grazed area.
Some of our research findings suggest that the reason for the apparent differences in deer numbers may be due to higher fawn survival on the ungrazed Three Bar. In recent years survival, as measured in January of each year, has shown about 15 more fawns per 100 does on the Three Bar than on Unit 22 as a whole. Also, we've found a positive relationship between winter precipitation and forb production (not surprising!) and then between forb production and fawn survival. This suggests that the lower fawn survival outside the Three Bar is probably due to a reduction in forbs available to deer because of heavy cattle use. Sounds reasonable enough.
I'm confident that if the effort were made some interesting data could be obtained by comparing deer pellet group counts inside and outside enclosures on various National Forests. Not long ago I sat in on one day of the grazing appeal hearing for the Tule Allotment in Tucson. Jack Adams had an interesting chart which showed the density of deer pellet groups on three areas was inversely related to the degree of livestock use. The heavier the use by cattle the fewer the deer pellet groups. Some of Don Neff's work on the Beaver Creek area yielded the same results. Heavy use by cattle on watershed 11 and 12 resulted in reduced use by both elk and deer. Nowhere have I been able to find evidence that the overgrazed ranges of today actually support more mule deer or receive heavier deer use than lightly grazed or ungrazed areas. If overgrazed areas were indeed conducive to high mule deer populations, there are many ranges in the state where we should literally have a deer behind every bush and tree! The fact that deer numbers have been down during the past 10 years or so despite the prevalence of overgrazing should speak for itself.
Merriam turkey: In recent years a significantly higher poult survival has been recorded in ungrazed areas than in heavily grazed situations. And why not? The Merriam turkey is another ground nesting species, dependent on good ground cover during the nesting season. Young poults are both more vulnerable to predation in overgrazed areas and also likely to have fewer protein-rich insects to feed on in areas with little in the way of herbaceous cover. Insects have been found to be extremely important in the nutrition of all young gallinaceous birds.
Elk: A number of studies in different states have demonstrated that elk do best in areas not grazed or lightly grazed by domestic livestock. Don Neff's studies at Beaver Creek here in Arizona showed that elk were affected even more than mule deer by heavy livestock use of study watersheds.
Bighorn sheep: The burro has been catching all the hell but there is evidence that cattle have more of an impact on desert bighorns than burros simply because they are more widespread and found in many bighorn areas where no burros are found. And don't misconstrue this as a defense of the jackass. I'm all for burro management. My management plan, however, would be to eliminate the last jackass from the western rangelands. I would even volunteer my vacation time to serve on such a management team!
Song birds: Just as elimination of ground cover by overgrazing degrades habitat for the ground nesting game birds I discussed before, it has the same impacts on many species of smaller ground nesting or ground feeding small forms of bird life. I won't dwell on it but there have been a number of studies that have shown the reduction in both species and in total numbers as a result of overgrazing.
Cottontail rabbits and blue grouse are similarly adversely affected by the elimination of ground cover that results from overgrazing. I could go on but perhaps I've made my point. It is difficult really to come up with any species that, in the long run, would be benefited. Like deer some species might initially be favored by the early stages of range abuse, but chronic overgrazing will eventually impact adversely even on jackrabbits, kangaroo rats, and pocket gophers. Let's face it: Overgrazing is bad for all forms of animal life that live on our rangelands--including the livestock responsible for the range abuse.