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Storm clouds at Cross Ranch National Park © Harold E. Malde

Cross Ranch Preserve, North Dakota

The 6,000-acre Cross Ranch Preserve is located along the Missouri River in central North Dakota, near Hensler. The bison herd started with the introduction of 14 animals purchased from a private rancher in North Dakota in 1986. The starter herd’s lineage was primarily from Custer State Park in South Dakota, with additions to the herd from Theodore Roosevelt National Park in the late 1980s. The herd of 180 head currently resides on 3,050 acres of northern mixed grass prairie, consisting of two separate units. Animals with Wind Cave backgrounds have recently been added.

west bison pasture at Niobrara Valley Preserve © Chris Helzer

Niobrara Valley Preserve, Nebraska

The 60,000-acre Niobrara Valley Preserve is located along the Niobrara River and north edge of the Sand Hills in north central Nebraska, near Johnstown. The first bison herd was initiated in the winter 1985-86 from several different private origins, and the second herd during the summer of 1999 by purchase of bison from both private and federal origins. The two herds totaling 600 head in the over winter population, currently occupy 19,500 acres of Sand Hills prairie, northern mixed-grass prairie, and riparian woodland-grassland communities in the Niobrara Valley. Bison pastures are spring burned on a five-year rotation to control invading trees, improve forage quality and provide a mosaic of landscape patches that maintains biotic diversity.

Winter color on the Konza prairie, Kansas © Chris Helzer/The Nature Conservancy

Konza Prairie Biological Station, Kansas

The 8,600-acre Konza Prairie is located in the Flint Hills of northeastern Kansas, just south of Manhattan. Owned jointly by the Conservancy and Kansas State University Foundation, the larger Conservancy portion (7,700 acres) is leased to Kansas State University, and the total unit is operated as Konza Prairie Biological Research Station by the Division of Biology. The site is dedicated to a three-fold mission of long-term ecological research, education, and prairie conservation. KSU introduced a starter herd of 44 bison in 1987-88 mainly from Ft. Riley Military Reservation, Kansas, as well as two other sources. The over-wintering herd size varies from 275-325 animals on 2,480 acres, with a fall culling-sale to achieve a year-round stocking rate of approximately 12 acre/AU. The facility features some high-tensile electric fences.

Bison in Tallgrass Prairie Preserve, Oklahoma © Harvey Payne

Tallgrass Prairie Preserve, Oklahoma

The 39,100-acre Tallgrass Prairie Preserve is located in the Flint Hills region of northeast Oklahoma, near Pawhuska. A donated starter herd of 300 head was introduced in the fall of 1993, which shared origins with the Medano Zapata herd. The herd of 2,100 over-winter bison (2,700 with spring calves) occupies a 23,464-acre year-round unit of tallgrass prairie and crosstimbers woodlands. Randomly selected growing and dormant season prescribed burns are used to improve seasonal forage quality and to provide a mosaic of landscape patches that maintains biotic diversity.

Medano-Zapata Ranch, Colorado © Erika Nortemann/The Nature Conservancy

Medano Zapata Ranch, Colorado

The 100,000-acre Medano Zapata Ranch is located in the San Luis Valley of south-central Colorado, east of Alamosa and adjacent to the Great Sand Dunes National Park. The Conservancy purchased the ranch in 1999, which included a resident herd of several thousand bison and elk. The starter bison herd originated from several private and state herds from Wyoming in 1985. The previous owner managed the bison for production at first, but by the time Conservancy acquired the herd, the primary interest of the manager was in their conservation. The mitochondrial genetics of 200 cows were assessed in the fall of 2004. The results showed that 4.5% of the herd’s cows had bovine genes. Male bison are currently being assessed.

An extensive study of the ecology of bison and elk was undertaken by a consortium of partners, funded largely by the National Park Service, and led by U.S.G.S. scientists. The data is now being analyzed. The current bison herd of 1,400 head occupies about 48,000 acres of arid shrublands with interspersed wet meadows and is considered a conservation target. The Medano Zapata Ranch occurs in a native landscape of more than 400,000 acres which includes Conservancy, National Park Service, U.S. Fish and Wildlife Service and Colorado Department of Natural Resources lands.

Bison at Ordway Prairie in South Dakota © Mary Miller

Samuel H. Ordway Memorial Prairie, South Dakota

The 7,800-acre Ordway Prairie is located in the Prairie Pothole region of north central South Dakota, near Leola. Bison were first introduced at this preserve in 1978 under a year-round resident herd lease arrangement with a private bison rancher. In 1984, the Conservancy decided to acquire its own bison herd and the first 18 animals were purchased from a private bison rancher in South Dakota. The herd now contains 280 head on 3,600 acres of northern mixed-grass prairie.

Bison at Ordway Prairie © Eric Hoff/TNC

Slim Buttes Project Herd, South Dakota

Wind Cave National Park (WCNP) has maintained a closed breeding herd since 1916, having started with 14 animals from the Bronx Zoo and six from Yellowstone National Park. In October 2005, WCNP dispersed 20 bison to the Conservancy, which was the first bison dispersal outside of National Parks or tribal entities. These 20 bison tested as genetically unhybridized and disease free. The herd, Slim Buttes Project Herd, has been supplemented twice from subsequent WCNP dispersals. The Conservancy is working closely with Texas A&M genetic researchers to ensure genetic vigor as the herd grows. The 70-head herd is located on a 565-acre conservation buyer property adjoining WCNP and Custer State Park. Plans are to move the herd eventually to a Conservancy project in northwestern South Dakota. Until then, surplus animals are being used to start the Conservancy’s Broken Kettle Grasslands herd in the Loess Hills of northwestern Iowa and to supplement American Prairie Foundation's new herd in northeastern Montana.

The chalk bluffs at Smoky Valley Ranch. © Jim Griggs

Smoky Valley Ranch, Kansas

The 17,000-acre Smoky Valley Ranch is located in the High Plains of western Kansas, near Oakley. About 100 head of bison graze 3,110 acres of mixed grass prairie on the southern end of the ranch. The herd was introduced in early 2000 using 30 bred cows and two herd bulls donated by a private bison rancher. The bison handling facilities are currently being upgraded.