While considerable collecting of fossils in the Badlands has been done by various organizations since 1870, it was conducted in a somewhat random manner at first. Since 1899 the South Dakota State School of Mines and Technology has sent students into the Badlands for brief field studies.[45] However, it was not until 1924 that a systematic means of collecting fossils in the Badlands was begun by a Princeton University professor, Glenn L. Jepsen, who was studying at the South Dakota State School of Mines and Technology. He organized the first School of Mines Badlands Expedition, which met with immediate success and laid the foundation for the present extensive paleontological collections of that school (See Figure 5).[46] For many years large herds of bison roamed the Badlands during the summer months. About 1861, the year that the Dakota Territory was established, a drought began and continued for three years. The buffalo which used the region as their summer range left during that period. After the passing of the drought years, the herds, which had been driven far to the west by hunters, returned only in small bands. For a time great herds of mountain sheep, elk, antelope, whitetail and mule deer continued to roam the area in large numbers. The elk wintered in the southern Black Hills and went down into the Badlands in early spring. In 1877 residents of the Rapid City area and market hunters from the gold camps in the northern Black Hills killed large numbers, which ended the elk migration to the Badlands. Antelope as well as whitetail and mule deer were killed by market hunters and settlers. The mountain sheep was the last of the big game animals to disappear.[47] [Illustration: Figure 6 Jim Hart of Scenic, South Dakota, displays a trophy of an Audubon Bighorn Sheep shot on Sheep Mountain in 1903 by Charley Jones. These animals were last recorded on Sheep Mountain Table about 1910 and are now extinct.[48]] Predatory animals such as coyotes, wolves, and black and grizzly bears were likewise common. Bears were exterminated early. It was during the second decade of this century that coyotes and wolves disappeared from the Badlands, largely as a result of the work of the Biological Survey in its predatory-animal extermination program.[49] [Illustration: Figure 7 GRAY WOLF Adult animals weigh between 70 and 120 pounds and are the largest of the wild dogs. They were last seen in the present Badlands National Monument around 1913.[50]]