 Frogs are much more vocal , especially during the breeding season when they use their voices to attract mates . The presence of a particular species in an area may be more easily discerned by its characteristic call than by a fleeting glimpse of the animal itself . In most species , the sound is produced by expelling air from the lungs over the vocal cords into an air sac or sacs in the throat or at the corner of the mouth . This may distend like a balloon and acts as a resonator , helping to transfer the sound to the atmosphere , or the water at times when the animal is submerged . The main vocalisation is the male 's loud advertisement call which seeks to both encourage a female to approach and discourage other males from intruding on its territory . This call is modified to a quieter courtship call on the approach of a female or to a more aggressive version if a male intruder draws near . Calling carries the risk of attracting predators and involves the expenditure of much energy . Other calls include those given by a female in response to the advertisement call and a release call given by a male or female during unwanted attempts at amplexus . When a frog is attacked , a distress or fright call is emitted , often resembling a scream . The usually nocturnal Cuban tree frog ( Osteopilus septentrionalis ) produces a rain call when there is rainfall during daylight hours . 
