Ultrasonic distress calls and associated defensive behaviors in Neotropical frogs

Species have developed several defensive strategies for survival in response to predation pressures, including chemical, acoustic, visual, and behavioral mechanisms. Anurans serve as prey for numerous species, leading to the evolution of a diverse array of antipredator strategies. Among these strategies, acoustic emission defenses are categorized into distress calls, alarm calls, and warning calls. Although distress calls in frogs have been recognized to occur within the audible spectrum, the occurrence of ultrasound calls has been suggested for one species, but not yet confirmed. Based on our observations, we confirmed the presence of ultrasound distress calls emitted by an adult Haddadus binotatus. The distress call exhibited a high-pitched tone with decreasing frequency modulation and ultrasonic harmonics extending up to approximately 44 kHz. The presence of ultrasound frequencies in distress calls may confer advantages in deterring a broader range of predators. The use of broad-band screams synchronously with other behaviors, as raising the front of the body while arching the back and extreme mouth-gaping, intensified the defensive display, likely being more efficient in deterring predation. We observed similar behavioral repertoire for an adult Ischnocnema cf. henselii. Therefore, it could be widespread across individuals of other Brachycephaloidea genera as well.