Big Hole National Battlefield was inventoried for reptiles over 8 days on two separate periods during July and August, 2002. Sampling techniques used in the inventory included visual encounter surveys, incidental observation, and road surveys. The primary objective of the 2002 inventory was to document 90% of all reptiles that potentially occur within Big Hole National Battlefield. The University of Idaho Department of Fish and Wildlife Resources conducted the 2002 inventory under a cooperative agreement with the NPS
A total of two species of reptiles were expected to occur in the Big Hole National Battlefield and both were confirmed in the inventory. The reptile species with the highest abundance during the survey was the common garter snake (pa’yos, Thamnophis elegans). The other species was the western terrestrial garter snake (Thamnophis elegans). There were over thirty common garter snakes found on several occasions in the shrub riparian habitat type! Over 15 individuals, including both juveniles and adults, were present at one of these encounters, and this may have been a den site. Both of these snakes are nonpoisonous and do not pose a serious risk to visitors.