There is no resident fish population in the monument. Occasionally, when Chicken Creek flows, one or two species may briefly enter the monument from downstream sources.

In 2003, the National Park Service and Wyoming Game and Fish Department conducted an informal fish survey near the confluence of Chicken Creek with Twin Creek, just outside the monument boundary. Twin Creek produced seven native species including redside shiner, speckled dace, longnose dace, leatherside chub, bluehead sucker, mountain sucker, and mottled sculpin. A non-native white sucker was also captured.

More than 100 species of birds, mammals, snakes, and amphibians have been documented. Probably only the list of large mammals approaches the 90% level of completeness. Reptiles and amphibians are uncommon; only 5 species have been documented. One or two fish species enter during the brief period Chicken Creek is flowing. Fry and fingerlings have been observed in ephemeral pools near the boundary, but they have not been identified. Pronghorn, jackrabbits, least chipmunks, and Richardson ground squirrels are probably the mammals most often seen. A variety of songbirds are present, and kestrels, northern harriers, red-tail hawks, and golden eagles are common summer residents.

Mule deer, and a few moose reside throughout the year. Elk are seen occasionally in summer and a few may reside throughout the year. More Mule deer migrate onto the Monument during the fall, and early winter, and they remain until late spring, leaving as land north of the Monument becomes snow-free. A herd of more than 100 elk spends part of the winter on the Monument. Elk use appears to be increasing, and this could become a problem. Pronghorn are commonly seen from late spring into late fall or early winter. Pronghorn usually migrate to wintering areas outside the Monument as soon as the snowpack be accumulates in late fall or early winter.

Credits and Sources:

“Fossil Butte: Fish,” National Park Service, http://www.nps.gov/fobu/learn/nature/fish.htm

“Fossil Butte National Monument,” National Park Service, http://science.nature.nps.gov/im/units/ncpn/assets/docs/park_descriptions/fobu_description.pdf, Accessed on June 29, 2015.