In July of 1935, the game preserve became part of Wind Cave National Park. During the early years of the preserve, the animals were kept in small enclosures. Eventually, it was realized that they needed more space. The bison and elk needed additional forage and the pronghorn needed room to escape from predators. With the help of the CCC, fences within the park were removed. And in 1946, 16,341 additional acres were added, enlarging the park to 28,059 acres.

During the 1950's and 60's, park wildlife was the focus of much attention. Because of the lack of large predators, like wolves and grizzly bears, the bison and elk herds had grown to the point that they were literally "eating themselves out of house and home." Park rangers began to evaluate the carrying capacity of the park. Carrying capacity is the number of animals that can exist in a habitat without damaging it. To solve the problem of overgrazing, the bison and elk herd sizes were reduced. Park rangers began an active program to manage the herd size. They began rounding up the animals and shipping the excess live from the park to other parks and reserves. Rangers also worked to improve the grassland by reseeding overgrazed areas with native grasses and controlling exotic plant species.

In the 1970's and 80's, managers continued to focus on caring for the wildlife and rangeland by building an understanding of how the natural systems should function. The reintroduction of fire as a natural means to improve the range and to limit the expansion of the forest onto the prairie was researched. An active fire program was started, with the first prescribed fire occurring in 1972.

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