Diario de cabrillonationalmonument

What are those graphs all about? These are graphs called "sonograms," which bat biologists use to identify bat species. The graphs are produced by bat detectors which are set out for a period of time (usually 1-2 weeks). These detectors record every ultrasonic noise that occurs during the night -- so in addition to bat calls, they will pick up rodent calls. Each bat produces a call unique to their species -- on the sonogram, they are called "signatures."