The popular claim that wildlife species native to the American West’s arid ecosystems depend upon livestock waters for their survival is a popular one, but it’s not that simple.
Unfortunately, many federal land managers believe it. Several years ago, for example, I accompanied U.S. Forest Service staff on a horseback inspection of a livestock grazing allotment in the arid Superstition Mountains of the Tonto National Forest in central Arizona. As we neared a muddy stock tank perched on a chaparral-covered hill we scared off several mule deer that were taking a drink. The District Ranger turned toward me in his saddle and told me how glad he was that livestock were allowed to graze public lands, because deer would be scarce if there weren’t any livestock waters.
Most ranchers also seem to believe in it too, because they frequently offer it in defense of livestock grazing on public lands. I’ve even had ranchers tell me there was hardly any wildlife in Arizona before ranchers arrived and “improved” the land, which is, of course, ridiculous (Davis 1973).
Despite all these opinions, there’s a lot of scientific evidence that contradicts this widely held belief. Even long-time proponents of livestock waters question their effectiveness (Brown 1997; Krausman 1997). For instance, a review of the Arizona Game & Fish Department (AGFD) bighorn sheep water development program (Broyles 1995) conducted in the Cabeza Prieta National Wildlife Refuge concluded, “It has not been shown that these developments are necessary, beneficial, or without harmful side effects.”
Many wildlife species will travel further than cattle to reach water (Krausman 1996), and they know where the local seeps, springs, and perennial stream stretches are located. A study conducted in southern New Mexico (Burkett 1994) compared wildlife populations at 20 sites that had man-made waters with the same number of similar sites lacking permanent surface water. They found that, “definitive effects of artificial water sources on native wildlife species were not detectable.”
And another study conducted in Arizona’s Sonoran Desert (Krausman 1995) looked at desert mule deer and bighorn sheep populations in the area of the Central Arizona Project canal before and after its construction. They found that, “additional water was not important to the deer or sheep populations.” And a more recent study of mule deer distribution in arid environments (Marshall 2006) found that, “Water in the absence of forage and cover likely will not create mule deer habitat, but forage and cover in the absence of water may provide deer habitat.”
Building new livestock waters in upland areas is often justified by claiming they will lure cattle away from ecologically important riparian bottomlands. But cattle are bred to be lazy critters, and are unlikely to climb a hill in the summer heat to get a drink when the they can stay in the shade of a tree along a stream. Research (Carter 2017) has shown that, unless the riparian areas are fenced to exclude cattle, the new waters don’t significantly improve the condition of the riparian areas, but primarily facilitate rotational grazing and more livestock on the surrounding uplands.
The construction of new livestock waters in upland areas is supposed to help improve livestock distribution. The idea is to spread the cattle out more evenly and give them access to more forage. It can help frequently used areas recover from overgrazing, but it can also bring the negative ecological impacts of grazing, such as competition with wildlife for limited forage, to new areas that were historically unused by livestock (McAuliffe 1997). They can also create spatial competition between cattle and wildlife, such as elk and deer, which prefer to move out of areas when cattle are present (Wallace 1987).
If new livestock waters are built on desert land, they can facilitate wildlife habitat degradation by allowing the cattle to stay on the land longer during the hot summers and droughts. After the cattle denude the desert land of its limited number of herbaceous plants, which they prefer to eat, they then must resort to eating brush, mesquite seed pods, and low-hanging tree branches to try and avoid starvation (Smith 1993). In fact, research (Rosiere 1975) has shown that cattle grazing the Southwest’s deserts don’t get more than 50% of their forage from perennial desert grasses. This means that desert mule deer, for example, which prefer to eat woody plants, must compete with cattle for browse, especially during hot times.
Furthermore, new livestock waters in the uplands are often created by sinking a pipe into a natural spring and sending the water to a watering trough located away from the spring. The construction of these types of waters are often subsidized by state game management agencies because big game species can use them too. If the spring source is fenced off, it can stop cattle from tearing it up, but these diversions can significantly reduce, or practically eliminate, the amount of water available to the riparian habitat and dependent wildlife, especially non-game species, that were supported by the spring. This ecological damage is amplified when springs produce less water during droughts.
Statewide, the AGFD maintains more than 3,000 man-made watering sites in remote locations around Arizona. The agency and its private partners deliver up to 1.5 million gallons of water to these catchments every year, at an average annual cost of about $1 million. Many of these waters are truly dedicated to wildlife, as cattle are fenced out of them. But some are being built to primarily water cattle, offsetting the benefit they may provide to local wildlife.
And even if a new livestock water can provide some net benefit to the local wildlife, those benefits disappear if the rancher doesn’t maintain the water when cattle aren’t using the pasture.
Still, the idea that more water means more wildlife sounds intuitively good. It’s an easy concept for hunters and hikers to believe because they know one of the best places to spot wildlife is around water holes. But just because animals congregate around water holes doesn’t mean they’re relying on that water source for their survival. For example, how often have you stopped to take a drink from a water fountain just because it was convenient?
But what about all of those biologists warning us the majority of the West’s wildlife depend, in some way, upon riparian areas for their survival? Livestock waters rarely support significant amounts of riparian habitat. Many of them are so trampled by cattle they are considered ecological sacrifice zones.
Numerous studies have shown that it’s the amount and quality of suitable habitat that has the most influence upon wildlife populations. For instance, AGFD research showed that Gambel’s quail (Callipepla gambelli) don’t need surface water, and the quantity and quality of forage was the most important limiting factor on quail populations (Gallizioli 1961). In other words, water is just one component of wildlife habitat, and most Western U.S. wildlife species are adapted to its scarcity. In fact, many desert animals can go without water for a long time because they get it from the succulent vegetation they eat, or internally make their own water from the plants they eat. Its’ true that severe drought stresses these animals too, but livestock waters can help keep cattle on the land during drought – making the situation worse.
The bottom line is the ecological effects of building livestock waters should be objectively assessed for net benefits to the local wildlife. Sufficient vegetation to provide quality cover and forage appears to be more important than surface water for most arid land wildlife species. Furthermore, new livestock waters are expensive to build and on public lands they are typically built with public funds. In most situations, it would be cheaper for the taxpayers if federal land managers would simply cut permitted livestock numbers to achieve natural resource goals.