According to President Jefferson's instructions, Lewis and Clark kept detailed notes about the new plants and animals they found. As the Corps of Discovery crossed Montana, Lewis and Clark discovered and identified some of Montana's abundant plant and animal species. With such a perilous journey, it's amazing that many of the plant species and journals survived in relatively good condition.
Thomas Jefferson instructed Lewis in a detailed letter to observe "…the animals of the country generally, and especially those not known in the U.S. the remains and accounts of any which may [be] rare or extinct."
The journals of Lewis and Clark are bulging with biological information from their continuous attention to daily events and observations. The journals contain the first scientific descriptions of wildlife in the Missouri and Columbia River drainages. Lewis was adept in observing and systematically recording features which would have seemed trivial to even well-trained scientist. Lewis made physiological and ecological notations along with observations as to the abundance or scarcity of wildlife in certain areas.
Lewis and Clark identified such species as the: mule deer, pronghorn antelope, bighorn sheep, kit fox, prairie dog and several other rodents, sage grouse, blue grouse, western grebe, Lewis' woodpecker, western tanager, and numerous other song birds, several fish species, such as the cutthroat trout and Arctic grayling, and various reptiles and amphibians.