The 164,000-acre monument contains the highest known density of archaeological sites anywhere in the U.S, according to the BLM.
Tucked away in remote Tsegi Canyon, the monument surrounds a small desert oasis, a place abundant in plant life, with mountain mahogany, Gambel oak, serviceberry, rice grass and Douglas fir scattered across the canyon.
The fossil nests, dating to about 220 million years ago, are similar to modern-day crocodile and turtle nests.
Columbian mammoths ranged over much of what is now the southern United States and Mexico up until the end of the last Ice Age, when they became extinct.
During the summer, Navajo families still live and farm the bottoms of Canyon de Chelly, Canyon del Muerto and Monument Canyon, all of which make up Canyon de Chelly National Monument in northeastern Arizona.
The researchers used aerial photographs, geologic maps and ground tests to develop “spectral classes” characterizing 12 distinct geologic and vegetation types found in the Horse Prairie Valley study area in southwest Montana.
The study also shows the Bering land bridge vegetation at the time consisted primarily of tundra plants and shrubs and was unsuitable for long-term habitation by large grazing mammals.