USGS researchers at the Arizona Cooperative Fish and Wildlife Research Unit are analyzing mark-recapture data collected by the Arizona Game and Fish Department from 2008-2019. The northern Mexican gartersnake (Thamnophis eques; hereafter NMGS) is a federally threatened species occurring in riparian areas in central and southeast Arizona and west-central New Mexico. While previous studies have examined the ecology of this species in central Arizona, less is known about NMGS ecology in the grassland landscapes of southeast Arizona. This project continues a long-term mark-recapture study of NMGS in the upper Santa Cruz River in the San Rafael Valley of southeast Arizona. Abstract narrative source: USFWS Cooperator Science Series Report.