Kennedy, J. R.; McCreery, H.; Jones, A.; Spotted Horse, D.; Chen, C.; Fairfax, E.; Werfel, J.

Beavers are famous for building extensive damming complexes<1>, which can extend over kilometer-scale distances<2> and persist for centuries<3>. Dams have major impacts on their surrounding environment, including effects on the hydrology, geomorphology, and ecosystems of the area<4>. Current understanding of how the environment in turn affects beavers building activity centers on the single auditory cue of running water, based primarily on captive studies<14,15>. Observational challenges have limited a more detailed picture of the full feedback loop between beavers and their environment. Here we describe the detailed progress of new construction by 20 beaver colonies in northwest Montana, through field studies using drones to obtain surveys with spatial and temporal resolution each three orders of magnitude finer than typically reported<5-13>. We show that both the timing and location of beaver construction activity are influenced by environmental factors. Initiation of trail clearing, a stage preceding dam building, was associated with a narrow range of stream flow rates. Beavers preferentially built in locations associated with preexisting canals. These results emphasize the importance of non-dam elements in the beavers construction and its coordination across the colony, and point to environmental feedback processes that may span across years and unrelated colonies.