Range Management and Biodiversity

“I know that in the time that we’ve had part of the ranch… We have made it better… We’re leaving more grass… I think we can get through a longer dry spell just because we have a better root system and we’ve left more grass.”—Bruce Switzer

The Sandhills prairie was long ago designated as rangeland. That is, it was determined that its best agricultural use was for grazing cattle on the region’s abundant native grasses and other plants. There are more than 670 native species of vascular plants in the Nebraska Sandhills. Compared to grasslands with similar sandy soils and moderate rainfall, plant diversity in the Sandhills is high. This in part is due to the region’s abundant groundwater. The variety of plant species—a mix of native grasses, sedges, and forbs found in both tall-grass and short-grass prairies—makes the Sandhills prairie unique among grasslands. Although much of the vegetation can be found elsewhere, there are a few species that grow only in the sandy areas of the Sandhills, including blowout grass and the endangered Hayden’s (blowout) penstemon (Penstemon haydenii). Maintaining high diversity in this region is dependent on rangeland management that is based on an understanding of ecology. Fortunately, the Nebraska Sandhills are considered “one of the best managed large tracts of rangeland in the world.”

The Switzers use different grazing systems across their ranch to meet various land management goals, including maintaining the biodiversity of both plants and animals. One such system is called a deferred-rotation grazing system. The Switzers use two different deferred-rotation grazing systems—each divides pastures into five grazing units. Because different plant species grow at different times of the year, resting periods are based on when preferred species begin their growth cycle. The cattle graze in each unit once during the summer season. The next summer, the Switzers start a new rotation, but in a different order, to allow the longest possible resting period between grazing so that the vegetation has enough time to recover and grow. This is an important aspect of rangeland management in the Sandhills.

If the vegetation is overgrazed, leaving sand exposed to the wind, the dunes may become unstable, and blowouts may form. Small areas of erosion can develop into a blowout within two years if it is not “healed” with vegetation. Blowouts range in size from a few square yards to 250 acres. To protect the range from developing blowouts, ranchers set fences to prevent trampling and removal of vegetation by livestock in sensitive areas.

Although blowouts are of concern to ranchers who work to stabilize these sandy areas with vegetation, some plant, and animal species are highly adapted to this environment. Allowing blowouts to develop naturally in some areas helps to maintain biodiversity in the Sandhills. Recognizing the importance of balancing range management with species conservation, the Switzers work together with scientists from the University of Nebraska to monitor and manage a variety of species on their ranch.

The Sandhills are at the geographic center of North America and a stopover along the Central Flyway. Over 300 species of birds inhabit this region. Many birds migrate through the Sandhills, including the American white pelican, swans, bald eagles, and cranes. There are only a few bird species that are endemic to the Sandhills. Among these are the greater prairie chicken, upland sandpiper, and long-billed curlew. The region provides critical breeding and nesting habitat for resident bird species, like the greater prairie chicken (Tympanuchus cupido).

Prairie chickens typically mate in the Sandhills in late April. To attract females, 8 to 20 male prairie chickens perform a thunderous “booming” dance on specific mating arenas called leks. Leks are primarily found in sub-irrigated meadows where trimmed vegetation—the result of grazing and haying practices—makes it easier for female prairie chickens to observe the colorful dancing males and select a mate. Just before dawn, the males arrive on the lek. Low, hollow moans echo across the short grass before the birds are visible. As the sun breaks across the surrounding grass-covered dunes to the east, the booming calls gradually rise to a thrum, and the frantic dance begins. The dancing males lower their heads and raise their black, ear-like feather tufts, fan their tail feathers, and inflate orange air sacs on either side of their necks while stutter stepping in circles. The males announce a direct competition with loud squawking and furious flapping wings.

In an aggressive display of dominance, two males leap into the air toward one another—feathers flying. The females enter the arena to observe the ritual. They quietly select a mate or move on to the next lek. Once they’ve mated, the females move to the tall grass where they each build a well-hidden nest on the ground that they line with grass. They usually lay 10 to 12 eggs, olive-colored with dark brown speckles. The females incubate the eggs for up to 25 days. Hatchlings must find their own food—seeds, berries, leaves, and insects. Within two weeks, the young begin to take flight but stay with their mothers for nearly three months. Male prairie chickens return to the same mating ground year after year.

The Switzers have identified many leks on their ranch and work to manage this unique habitat for the benefit of grassland birds like the greater prairie chicken and sharp-tailed grouse. Prairie chicken populations evolved with grazers like bison. They thrive on a mix of native short-grass and tall-grass prairie with few trees. Prairie chickens benefit from range management strategies that introduce periodic grazing and fire to prevent the growth of trees, particularly the spread of invasive species like the Eastern red cedar.

There are 55 species of mammals that inhabit the Sandhills. The mosaic of prairie wetland—from low moisture dune tops to inter-dunal wetlands to riverbanks—attracts a number of mammal species that are also found in regions to the east and west and north and south. Species like the Ord’s kangaroo rat (Dipodomys ordii), which are more typical of the arid Southwest, are found in the Sandhills alongside species typical of colder northern climates like the meadow vole (Microtus pennsylvanicus).

Vertebrate ecologist Keith Geluso studies the distribution and number of species in an ecosystem. He is collecting valuable data to map biodiversity on the Switzer Ranch, which will help inform conservation and rangeland management decisions. Of particular interest to Geluso is the Ord’s kangaroo rat, which prefers an arid, sandy grassland habitat. The Switzer Ranch, situated on the eastern edge of the Sandhills, is ideal habitat for this species. The kangaroo rat primarily feeds on seeds. As an ecologist, Geluso studies how these animals move seeds around the landscape. Kangaroo rats gather seeds in their fur-lined external cheek pouches, but cannot eat all at once the seeds that they collect, so they distribute them in small caches or piles buried in the sand to save for later. Often they lose track of these seeds and unintentionally plant them, which contributes to the overall plant biodiversity and productivity of the prairie. The new plants will grow and feed more kangaroo rats and many other organisms—and the cycle will begin again.