Using precise tracking technology, Oregon State University researchers have determined that cattle spend less time in streams than most people think—the average is between 1 and 2.5 percent of their time on the range.
In a five-year study recently published in the Journal of Soil and Water Conservation, John Williams and his colleagues placed GPS collars on cows and sent them out to graze with their herds across large acreages of rangeland in eastern Oregon.
The researchers mapped the cows’ positions over the paths of rangeland streams across five spring-to-fall grazing seasons. They discovered that the cows went down to the water when they needed to drink or cross, but did not typically rest or hang out there. They spent most of their time grazing on higher ground or resting on dry areas away from the stream.
“Our goal in this research was to provide some needed basic information about how livestock interact with streams,” said Williams, an Extension rangeland expert in OSU’s College of Agriculture Sciences based in Wallowa County, Ore.
Affordable GPS technology, he said, has made it possible to gather such information at very high resolution. “It used to be you had to send a grad student out there for hours on end to count where the cows go. That’s not practical across large swaths of rangeland.
“So up to now we haven’t had good quantitative data about cattle’s use of streams on the range.”
Cattle grazing, especially on public lands, has been controversial at least since the 1980s, when ecological studies started to document the environmental damage done to rangelands from a 150-year history of livestock grazing.
These findings and public pressure led to the adoption of grazing management practices aimed at protecting streams while still allowing livestock use. Today, all ranchers with allotments on federally managed grazing lands follow plans worked out with the appropriate management agency.
In 2008, Williams and his colleagues started tracking the movements of herds grazing three federal allotments in the Wallowa-Whitman National Forest in northeastern Oregon. The study sites comprise about 170 square miles of forest and rangeland. All grazing was conducted by private ranchers under approved grazing management plans.
In each allotment, 10 cows out of a herd of 300-400 were fitted with GPS collars at the start of the grazing season, typically April to June. The collars recorded the cows’ locations about every 5 minutes, yielding more than 3.7 million data points over the five-year study.
The researchers found that the cattle’s movement patterns were influenced by a host of factors, including the locations of preferred forage and water sources, fences, and areas previously logged or burned. The point of entry for the herd at the beginning of the season also made a difference in the roaming patterns, as did the mountainous topography.
The cattle were not particularly drawn to the streams, Williams said. They went down to the water at favorable access points to drink or to cross to other grazing areas, but did not typically linger there.
In addition, the cows used about 10 to 25 percent of the stream area. The rest of the streamside areas were lightly visited, or not at all, because streams were inaccessible or streambanks were steep or slippery.
“As long as the cows could get to water when they needed it, it appeared that they were more influenced by where the best forage was than by anything else,” said Williams. He noted that all the study areas also contain non-stream sources of water, such as developed springs and ponds. In a related publication, the researchers analyze the cows’ use of these alternate water sources.
The results weren’t exactly a surprise, Williams said; OSU research dating from the 1980s suggests that cattle don’t spend much of their time in the water. “But how many data points can you get with a grad student out there watching a cow? Now, with this GPS technology, we can get a body of data we can really analyze, and we can start answering some of these controversial questions with confidence.”
The research was supported by the U.S. Department of Agriculture’s National Institute of Food and Agriculture, and Agricultural Research Service; the Oregon Beef Council; the Oregon Agricultural Experiment Station; the University of Idaho; and the International Center for Agricultural Research in the Dry Areas.