Lands_Content Page_Sandhill Natural history and management

Sandhill Wildlife Area's Natural history and management

Sandhill Wildlife Area is managed as a wildlife demonstration area, a living laboratory used by wildlife biologists and researchers who test new wildlife management techniques designed to increase the abundance and diversity of wildlife native to the area. Sandhill has also been used to test the effects of manipulating hunter and trapper numbers, their hunting or trapping methods, season lengths and bag limits. Wildlife researchers evaluate these methods for application in other parts of the state.

Wetlands

Our local weather delivers about 32 inches of water as rain and snow each year. Excess rainwater runs off the surrounding hills and collects in natural, shallow marshes or in basins called flowages created by our technicians. In drought years, the marshes and flowages are dry, cloaked in grasses, sedges, bulrushes and cattails with willow and alder brush rimming their edges.

Our wetlands are extremely valuable for a number of reasons:

  • Wetlands provide lush vegetation used by resident wetland wildlife for food and shelter.
  • Wetlands are used by migrating birds during their spring and fall trips. These birds can rest and feed here before taking the next leg of their journey.
  • Our wetlands provide one of Wisconsin's largest migratory staging areas for sandhill cranes. More than 1,500 sandhill cranes may visit our marshes during the fall flight.
  • Wetlands serve as nurseries for muskrats, ducks, amphibians, insects and fish.
  • Wetlands improve our drinking water quality by trapping sediments and filtering impurities from rainwater runoff before it mingles with the groundwater below.
  • Wetland plants use the naturally occurring elements of nitrogen and phosphorous that would otherwise cause rampant weed growth and algae blooms in the water.
  • Wetlands help control floods during bouts of heavy rain.

Wetlands support more biological diversity than any other habitat in Wisconsin, and their value cannot be overstated.

Wetland management

Sandhill's wetlands are carefully managed through water level regulation and controlled burns.

Natural precipitation is the only source of water that collects in Sandhill's many marshes and flowages.

Wildlife technicians use various techniques to control the water level in these flowages. They create earthen dikes and elevated roads that keep the water higher on the upstream side. They install spillways on these dikes to rid flowages of excess water. Wildlife technicians also install and regularly manipulate water control structures specially constructed of culverts that pass beneath the earthen dikes and roads. The management staff may either remove or add stop logs that are stacked on top of each other in a vertical, or riser, culvert to lower or raise water levels. This system relies on gravity to move the water. If a wildlife technician removes logs from the riser, the water level drops. If a technician adds logs, then the water level rises. In spring and summer, the management team draws down the water level to encourage the lush growth of green seed-bearing plants that are important to migratory birds that stop at the flowages in the fall.

Where possible, the Sandhill wildlife management team drains wetlands on a three- to four-year cycle to mimic natural drought conditions. The mudflats that lay exposed after a wetland has been drawn down readily decompose dead plant materials and attract a variety of wading birds and shorebirds from the tiny solitary sandpiper and killdeer to the lumbering great blue heron-seeking tadpoles in lingering pools. The nutrients released through plant decomposition are readily used by sprouting plants after the basin is slowly reflooded. Water clarity and plant nutritional value typically increase following a drawdown.

In late summer, marshes that have been drawn down are burned, if weather permits. Fire helps reduce rank weed growth and the spread of shrubs that would eventually choke out plant life beneficial to wetland wildlife. Prescribed burns also clean out stagnant areas clogged with dead, decaying plant matter while releasing valuable nutrients trapped in the duff. These nutrients are then available for use by living plants and animals. Following the drawdowns and prescribed burns, the wildlife management team refloods the basins in late summer after the plant seeds have ripened. These reflooded marshes and flowages provide a welcoming resting spot and a well-stocked smorgasbord of food for a wide variety of migratory birds who will be winging their way south across Wisconsin in the autumn months. Thousands of migratory birds stop over at Sandhill to take their fill of our bountiful supply of food. Once an old flowage is rejuvenated in this manner, the benefits of our marsh management practices will last several years.

Forests

The Sandhill property's dry, sandy hills favor sun-loving aspen, jack pine and scrub oaks. The oldest stands date back to just after the last wildfire of 1930. Large, mature oaks provide tree cavities and downed branches used as shelter by woodpeckers, chickadees, nuthatches, squirrels and raccoons. Spring droughts favor acorn production and bumper crops of these high-energy foods sustain healthy populations of ruffed grouse, wild turkey and white-tailed deer. The ground beneath these oaks is quite open and grassy. This park-like condition doesn't provide enough good cover for ground-dwelling mammals. These creatures spend little time in old oak forests and favor dense, young forest growth.

At North Bluff, the presence of big-tooth aspen tells biologists that the soils are a little better here than in other parts of Sandhill where the soils are either too sandy or too soggy for aspens to thrive. Big-tooth aspen is seldom found on neighboring dry, sandy ridges. It can be distinguished from other trees by its smooth, greenish-yellow bark and tall, straight trunk. The aspen stand at North Bluff is growing past maturity and will soon be replaced by the abundant maple seedlings waiting patiently in the shade created by the aspens. In years of drought, our groundwater level drops beneath the reach of tree roots. Searing heat robs branches and leaves of moisture and some of the trees weaken and die above ground level. The roots hang on, however, sheltered deep in the soil. When the rains return the stumps sprout.

Forest management

Forests are actively managed at Sandhill Wildlife Area by allowing well-planned commercial logging. A logging operation conducted under a carefully prescribed forest management practice creates greater habitat diversity than a solid stand of mature forest. Diverse habitat, in turn, supports a wider variety of wildlife. However, loggers are not allowed to simply come in and cut away as they please. Timber harvests designed to benefit wildlife must be carefully and properly designed by our forester and wildlife biologist to ensure a good mix of various sizes, ages and types of trees left behind. The size and shape of the logged area are also important to consider when designing a timber harvest that is beneficial to wildlife. Our logging operations generally do not exceed 40 acres and they have irregular shapes to maximize edge. Wildlife diversity is high at the edge of two different habitats, so the more forest edge, the more wildlife.

To help loggers know what to cut and what to leave, the timber sale boundary is painted red to alert the loggers. Some trees are painted blue. These are to be left standing. Blue-marked trees may have cavities used by woodpeckers, chickadees, raccoons and squirrels, or they may provide especially good sources of acorns or other food for deer, grouse, squirrels, blue jays and other wildlife. Older white oaks are an example of one type of tree we often leave standing. Their acorns are highly prized as food because they are less bitter than acorns from the more abundant red oaks.

Many cuts on Sandhill allow for the natural regeneration of the trees. This works especially well with aspen and oak. These sun-loving trees readily sprout from the stump. By cutting these trees, our wildlife management team is able to retain the presence of these trees in the forest and stagger the age of timber stands throughout the area. This benefits many types of forest wildlife that utilize different age classes of trees for food and shelter.

In some areas of Sandhill, you may wonder if a tornado ripped through the area. Actually, our wildlife management team replicates the effects of natural wind storms. During winter, our wildlife management technician crew shears off the standing brush and small trees with bulldozers and chainsaws while the ground is frozen. Sunlight penetrates the forest floor stimulating the cut-over area to resprout. The downed and rotting logs provide a moist and earthy home for salamanders, moles, shrews, centipedes and more. Toppled trees are also important for forest regeneration because they provide a good growing medium, rich in nutrients that are slowly released as they rot. Tree and shrub seedlings need this to get a healthy start in life.

Prairies and barrens

Prairies are natural grasslands composed of native grasses such as little bluestem, big bluestem and Indian grass. These grasslands also have an abundance of summer and autumn-blooming wildflowers such as asters, sunflowers and fragrant members of the mint family, including spotted mint and wild bergamot. Sandhill's prairies are important habitats for a wildflower called wild lupine that supports the endangered Karner blue butterfly. Once, wildfires naturally kept woody trees and shrubs from encroaching onto the original prairies. The extremely deep and extensive underground root systems and underground crowns of prairie grasses and wildflowers are adapted to survive the fire. Prairies, composed of fire and drought-resistant plants, thrive on the sandier, drier soils of our wildlife area.

Fires also historically maintained another interesting wildlife habitat. Known as oak barrens, these habitats are actually open, prairie groves on poor, sandy soils dominated by prairie plants with oak trees scattered throughout. This habitat is maintained by repeatedly burning back the other woody vegetation. In former times, this burning was the result of natural or carelessly-set wildfires. Only mature burr oaks that have bark thick enough to withstand the destructive force of fire remain in this otherwise open, sandy soil prairie landscape. Oak barrens are inappropriately named for they are anything but barren from a plant and animal perspective. Animals and plants found in Wisconsin's oak barrens are among the rarest in the state. The federally endangered Karner blue butterfly and the dusky elfin butterfly are both dependent on wild lupines that thrive in our oak barrens. The Karner blue butterfly requires large patches of this stunning wildflower for nectar, a place to lay its eggs and its very survival. Look for the brilliant sweetpea-like purple flowers blooming from late May through June. Wildlife also values prairies and oak barrens for food, and sunlight and as a place to escape the pesky biting insects so common in our woods during summer months.

Prairies and barrens management

Fire is used by our wildlife management team to manage native prairies. When the fire is lit by people who do not possess the skill to manipulate fire, it can be a powerful and destructive force. Wildfires swept through this area in 1893, 1910, 1920 and 1930. Most of these wildfires are believed to have been set by landowners wanting to renew the valuable wiregrass growing in the marshes. When the fire is lit and then carefully controlled by an experienced and well-trained team, it becomes a powerful and useful tool for managing wildlife habitats.

Our Sandhill wildlife management team is currently taking steps to improve the oak barrens community, sometimes called the oak savanna community. One of our oak barrens projects is located within the Bison Barrens area. While this area may look expansive at 260 acres, it is really quite small. Beginning in 1996, wildlife staff took steps to double the size of the oak barrens. Most of this expansion took place to the north of the Bison Barrens and consisted of cutting and removing trees, burning the leftover piles of branches and planting native prairie grasses grass and wildflowers.

Oak barrens restoration is very time-consuming and costly. However, by creating this open savanna-type habitat, we increase visitors' chances of seeing the magnificent bison in their native habitat. Our management efforts also improve range conditions for the bison, provide educational opportunities for school groups and individuals and provide a home for rare, threatened or endangered wildlife, including the Karner blue butterfly.

The end result of our barrens management project will be a 500-acre upland oak barrens attached to the 2,200-acre Gallegher Marsh. We hope that this entire open landscape will attract much habitat-specific wildlife such as sharp-tailed grouse, bobolinks and other creatures who need large expanses of open landscape. Persistence and time will tell whether our management approach will succeed in putting a little bit of Wisconsin's natural heritage back on the landscape. Through a vigorous habitat management program of burning and mowing woody plants, the wildlife management team at Sandhill is able to maintain the semi-shade to full sunlight conditions that the wild lupine (and butterflies) prefer. The prairie must be burned periodically to maintain the habitat, an action that may result in the killing of butterflies, eggs or larvae. To get around this dilemma, the Bison Barrens are divided into parcels called burn units. Each unit is burned or mowed on a staggered time schedule once every three to seven years. Under this scheme, only one or two units are affected yearly and any butterfly losses within the affected units are quickly recovered through re-colonization from butterflies living in neighboring units.

Scattered here and there throughout the Sandhill Wildlife Area you may see small farm fields once used by farmers prior to the 1930s. Wildlife managers and technicians originally kept these fields planted with corn and buckwheat for wildlife. But, by the early 1970s, managers realized that the practice of maintaining food plots for wildlife wasn't the best management practice because it unnaturally causes wildlife to depend too much on people for their food supply. Today, trees and shrubs are reclaiming some of these fields. Other fields have been replanted with or reclaimed by native prairie grasses and wildflowers. Seeds from our restored prairies are sometimes collected in the autumn with the help of students from area schools. The seed is then used to establish prairies elsewhere.

Wildlife management

In the tradition that Wallace Grange started, Sandhill is still encircled by an enormous amount of fencing: 17 miles long and now 9 feet tall. It is considered a deer-proof fence. The fence makes it easier to tally the number of deer living on Sandhill because it eliminates movements onto or off of the property. Ninety percent of the deer born on Sandhill are eventually accounted for by hunters. Ten percent fall prey to predators or die from mishaps. Researchers gather data on the deer population at Sandhill by analyzing the sex and age of deer that have died. It generally takes eight to 10 years to account for all the deer born in any one year. However, the oldest deer recovered in Sandhill lived to be 15 years.

Twenty years ago, the remains of roughly 100 deer traps, designed by Wallace Grange, lay scattered across the forested Sandhill landscape. These were the vestiges of Hazel and Wallace Grange's Sandhill Game Farm operation. Beginning in 1947, the Grange's set out these traps each winter, baited with hay, cranberries and corn to lure and capture deer. They sold and shipped the deer collected in these traps to southeastern states to help bolster those states' declining deer populations. After the DNR acquired the Sandhill property in 1962, the deer traps were used to capture and ear-tag deer to study their movements and to determine sex and age ratios and harvest trends of deer on Sandhill.

One deer trap has been reconstructed as part of a high school independent study program conducted at the Sandhill Outdoor Skills Center. Area high school students, selected to study the movements of radio-collared deer, constructed the trap based on designs gleaned from memories of long-time employees and from salvaged rotting remains of an old trap found in the woods. Though the students expressed some doubt that it would work, work it did. Plans are to continue this study and continue using this trap for several years to come.

To remain healthy, white-tailed deer must eat 5 to 6 pounds of browse each day, or 600 pounds of buds, twigs and bark each winter. They are fond of white pine seedlings and evergreen branches. As you travel throughout Sandhill, take note of the pines in the area. Look for what we call the browse line. This is a uniform line that separates the dead branches from the green limbs of the pines and is caused by hungry white-tailed deer in winter. The green line is the point above which they cannot reach. Deer so thoroughly browse the green needles and tender twigs when stressed for food in winter, that they have completely stripped away the life in these trees below the line. The occasional green branches close to the ground were concealed by winter snow and kept from the deer's hungry mouths.

In one area of Sandhill, you will find what is known as a deer exclosure. This is a small area enclosed by a deer-proof fence. Visitors may compare the difference in the height of the white pines inside and outside the deer exclosure, all planted in 1962. The fenced-in area prevents deer access to the white pines. Notice the difference between the two. Researchers also conduct work on improving deer census techniques. High school students recently began a team investigation on the movements and spatial arrangement of deer by radio-collaring deer.