The foothill yellow-legged frog (Rana boylii) is a Species of Special Concern in California and a Category 2 Candidate for Federal listing. In April and May of 1991, in and along Santa Rosa Creek, Sonoma County, we used an aerial microphone and a hydrophone to obtain recordings of its vocalizations. Except for faint aerial calls given while a frog was clasped about the pectoral girdle by an investigator, the sounds were produced while the frogs were completely immersed in water. Representative tape recordings were analyzed by compl1ter using the MacSpeech Lab II program. Five different vocalizations were identified: a short, unpulsed call; a short, pulsed call given when frogs were clasped by the investigator, pulsed calls of two intermediate lengths; and a long call in which groups of pulses are clustered into notes. The extensive vocabulary of the frog suggests that it may use vocalizations for a number of behavioral functions, such as advertisement of territory, vocal defense of territory, and attraction of mates. This previously-unreported phenomenon of underwater vocalization by R. boylii has at least three implications for management ( 1) hydrophones could pote:ntially be used in field censuses to enhance the detection abilities of surveyors during the breeding season; (2) phonic aspects of the phenotype should be used in conjunction with molecular, morphometric, and other traits in studies of geographic variation; and (3) habitat analyses should be done with an awareness that calling males may have requirements that differ from those of egg-laying females.
|
