Ultrasonic communication in frogs

Area of Science:

• Bioacoustics
• Animal Communication
• Evolutionary Biology

Background:

• Ultrasonic sound production and detection (>20 kHz) were previously known only in a few mammal groups (bats, cetaceans, rodents).
• Most amphibians, reptiles, and birds have limited hearing (<12 kHz).
• The concave-eared torrent frog (Amolops tormotus) inhabits noisy, fast-flowing streams.

Purpose of the Study:

• To investigate ultrasonic communication and hearing in the amphibian Amolops tormotus.
• To determine if ultrasonic vocalizations are used for communication or are a byproduct of sound production.
• To understand the evolutionary drivers for ultrasonic capabilities in this species.

Main Methods:

• Field acoustic playback experiments in the natural habitat of Amolops tormotus.
• Analysis of vocalizations for ultrasonic components.
• Electrophysiological recordings of auditory midbrain responses.

Main Results:

• Amolops tormotus males produce bird-like calls with ultrasonic frequencies.
• Both audible and ultrasonic components of calls elicited vocal responses from males.
• Auditory midbrain confirmed ultrasonic hearing capacity in Amolops tormotus and a sympatric species.

Conclusions:

• Amphibians possess ultrasonic communication and hearing capabilities, previously thought to be limited to mammals.
• The evolution of ultrasonic capabilities in Amolops tormotus is likely a response to intense low-frequency ambient noise.
• This represents an independent evolution of ultrasonic perception in a distinct vertebrate lineage.