Males of most anuran species use acoustic communication to attract females. Rana aurora (Northern Red-legged Frog) is one of a few anuran species that calls underwater, making it difficult to survey using traditional visual and auditory methods. R. aurora are experiencing significant population declines and are listed as a sensitive species in Oregon. Lack of information on basic life-history strategies may limit conservation efforts. This study explored calling behavior and breeding phenology of R. aurora by quantifying seasonal and diel calling patterns. An audio recorder with an underwater microphone (called a hydrophone) was used to capture underwater vocalizations at Finley National Wildlife Refuge near Corvallis, Oregon, USA. Results suggest that male R. aurora chorus from January until March for up to 14 h per day at a time. This is a significantly longer duration than previously recorded. This study shows that passive acoustic surveys can improve the detection and monitoring of a cryptic species, which allows for better monitoring and surveying of this species.