Amphibians, birds, mammals, reptiles, and invertebrates abound at Big Hole National Battlefield. The Big Hole River flows through an area where it is common to see mule deer (Odocoileus hemionus) moose (Alces alces) and elk (Cervus nippon). And so, from the elk to the ant, species diversity is of critical importance.
A total of 31 mammals were confirmed at Big Hole NB in a 2002 study. Four herpetofauna (reptiles and amphibians) were also confirmed. The western toad (Bufo boreas) and the gray wolf (Canis lupus), are listed by the Montana Natural Heritage Program as “species of special concern”. Bald eagle (Haliaeetus leucocephalus) may be periodically seen in the park, but are not residents. Other sensitive species that may be found in the park include Montana arctic grayling (Thymallus arcticus), mountain plover (Charadrius montanus), swift fox (Vulpes velox), great gray owl (Strix nebulosa), and Boreal owl (Aegolius funereus).
The Columbia spotted frog (Rana luteiventris) is probably the most widely distributed and most abundant amphibian in the battlefield. The common garter snake (Thamnophis elegans) is the most widely distributed and most abundant reptile. The most abundant mammals at the battlefield are the Columbian ground squirrel (Spermophilus columbianus), the deer mouse (Peromyscus maniculatus), the meadow vole (Microtus pennsylvanicus), the red squirrel (Tamiasciurus hudsonicus), and the western jumping mouse (Zapus princeps).