Trails and canals emerge as beavers engage in dam building behavior. Trails form as vegetation is cleared by beavers. Beavers excavate canals by deepening trails, and these facilitate transportation of large, woody material. The dam building season in the Rocky Mountain west lasts three (3) to five (5) months. Canals can persist for years, and trails re-emerge every building season. This study tracks and quantifies beaver colony trail and canal construction and expansion in the foothills of the Rocky Mountains in northwestern Montana where spring floods annually wash out previous years’ builds, requiring beavers to rebuild from “scratch.” To observe trail and canal networks at high spatial and temporal resolution, we used a DJI Phantom 4 Pro drone to scan three (3) sites from May 2018 to August 2018. Using Agisoft Photoscan, we constructed high resolution (1.3 cm/px) orthomosaics. At each site, about one (1) scan per month was annotated with ArcGIS to create shapes files in order to track trail and canal lengths. We found that most colonies experienced a linear increase of trail and canal growth during the observed period. Trail formation preceded dam building by beavers. Among the 17 colonies identified, average trail and canal network length grew by about 5 km, and three (3) colonies exceeded 10 km of growth.