Frog love is loud.
The time for the cacophony of male frogs bellowing to find their mates is now and anyone who has had the pleasure (and perhaps pain) of being in the midst of a boisterous frog calling chorus knows that the sound can be deafening.
The noise of a lot of frogs vocalizing can exceed 100 decibels (think rock concert), a level that can cause hearing loss in humans. The Occupational Health and Safety Administration (OSHA) recommends that people should spend less than 15 minutes in a place where decibel levels exceed 80 to avoid hearing loss and damage.
So how do frogs do it, and even more intriguing, how do they find a mate among the noisy madness?
They listen with their lungs.
A frog’s auditory system if very different from a human’s. There is an open floor plan of sorts that includes their eardrum (or tympanum), Eustachian tubes, glottis, and lungs — all of which play a role in the frog’s ability to hear and distinguish desirable and undesirable sounds. Frogs can feel sounds through their ears and through their lungs, with detection and processing moving between the two organs in a sonic pathway.
A recent study on green tree frogs has shed new light on how female frogs can hear her potential mate among the roar of many different species and against a backdrop of background noise. She simply needs to take a deep breath. In a fascinating display of functionality, it seems that the frog’s lungs can act as noise-cancelling headphones, which reduce some sounds, allowing the tympanum to detect more important ones. The effect can be substantial, reducing unwanted background noise by 10 decibels.
When the female inflates her lungs she can absorb certain frequencies, allowing the ears to better hear other frequencies. The study showed that a female frog’s lungs muffle sounds in the frequencies used by other species of frogs, so her ears can pick up those in the frequencies of her own species.
In a nod to citizen scientists everywhere, the researchers were able to analyze and determine the frequencies of 42 species of frogs whose calls were recorded by community members. The researchers then narrowed the field and isolated the 10 most likely species to be singing in a chorus, explaining that these extra unwanted crooners, plus other background noise, if not lessened, could interfere with a female’s ability to hear appropriate (and same species) suitors and breed successfully.
With this trick up her sleeve (and in her chest cavity), and the vibrations up her Eustachian tubes, no hand wringing (only ear ringing) will be needed to find a mate. And at this season’s crowded frog singles bars, the males’ lusty choruses might be accompanied by a soundtrack of “I only have ears for you.” Let’s hope she is successful at filtering out the irrelevant and unwanted species.
However, since those lungs are within earshot she might not detect their superfluous songs at all.
Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.
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