Brett Addis, a Ph.D candidate at the University of

Brett Addis, a Ph.D candidate at the University of Montana, wades into a vernal pool to reach one of the three song meters installed at Travis Air Force Base, Calif., Feb. 13, 2017. The song meters are audio recorders designed to capture night vocalizations of the western spadefoot toad and are used as part of a study to detect the possible presence of the amphibian on base. During maintenance checks of the meters, Addis removes and replaces memory cards and batteries. (U.S. Air Force photo/ Heide Couch)