The giant garter snake (Thamnophis gigas) is a large, aquatic snake threatened by habitat loss. The historic occurrence of rice agriculture in the Natomas Basin allowed the snake to persist there, and conservation and monitoring programs outlined in the Natomas Basin Habitat Conservation Plan are designed to ensure its continued existence in the Basin. Sex ratios and size distributions of the giant gartersnake in the Natomas Basin in 2011 were consistent with a healthy giant gartersnake population. The giant gartersnake was broadly distributed throughout Natomas Basin Conservancy reserves in 2011 as well. Demographic monitoring suggested that the giant gartersnake was most abundant in restored marshes in the North and Central Basins, less abundant in rice in the Central Basin, and persists at low abundance in the Fisherman’s Lake Area. To learn more about USGS giant gartersnake research, visit: