Acoustic radiation patterns of mating calls of the túngara frog (Physalaemus pustuosus): Implications for multiple receivers

Abstract

In order for a signal to be transmitted from a sender to a receiver, the receiver must be within the active space of the signal. If patterns of sound radiation are not omnidirectional, the position as well as the distance of the receiver relative to the sender is critical. In previous measurements of the horizontal directivity of mating calls of frogs, the signals were analyzed using peak or root-mean-square analysis and resulted in broadband directivities that ranged from negligible to a maximum of approximately 5 dB. Idealized laboratory measurements of the patterns of acoustic radiation of the mating calls of male túngara frogs ͑Physalaemus pustulosus͒, along axes relevant to three receivers in this communication network, female frogs in the horizontal plane, and frog-eating bats and blood-sucking flies above the ground, are reported. The highest sound pressure level was radiated directly above the frog, with a 6 dB reduction radiated along the horizontal direction. Band-limited directivities were significantly greater than broadband directivities, with a maximum directivity of 20 dB in the vertical plane for harmonics near 6 kHz. The implications with regard to mating and predator-prey interactions are discussed.

Behavioral and neural auditory thresholds in a frog

“…Hearing threshold is also a critical variable for determining a signal’s active space, the distance over which receivers can detect a signal (Marten and Marler 1977; Brenowitz 1982; Lohr et al. 2003; Bernal et al. 2009b).…”

Vocal responses to noise reveal the presence of the Lombard effect in a frog

“…Using a reference signal of known amplitude, we estimated that this noise-subtracting method is reliable and provides conservative estimates under low signal-to-noise ratios. Another technical issue concerns directionality, as many animals (e.g., Patricelli et al 2007), and túngara frogs in particular (Bernal, Page, et al 2009), are not omnidirectional sound sources. Túngara frogs focus most of their acoustic energy between 45 and 90 degrees in an angle to the water surface (Bernal, Page, et al 2009) and recording frogs from these angles therefore assured that our amplitude measurements were not confounded by the directionality pattern.…”

Raising a racket: invasive species compete acoustically with native treefrogs

“…Indeed, H. versicolor (gray treefrog) offspring 428 performance is predicted by call duration, with offspring of fathers with longer duration 429 calls performing better across several fitness-relevant factors (Welch et al 1998 white noise of the same frequency), again suggesting a general response to masking 436 rather than anti-predator or aggressive behaviour. It is possible that the apparent increase 437 in amplitude during the masking stimuli could be due to the focal caller changing 438 orientation during the stimuli (Bernal et al 2009). However, focal frogs were typically 439 found facing the same direction at the end of the trial, making phonotaxis an unlikely 440 explanation but one worthy of further investigation.…”