Behind the Cover: May 2021

The research: Animals have devised various strategies to communicate over the ambient noise of their habitats. The red-eyed tree frog, featured on the cover of the May 2021 issue, adopts a brute-force approach: It simply tries to call to potential mates more loudly than other species, even above 100 dB, roughly the volume of a motorcycle. Female green tree frogs, on the other hand, have developed an alternative approach. Inflating their lungs attenuates a noisy frequency band, thus enabling them to better hear the calls of their male suitors amid the din. Check out the story on page 17 for details on how researchers discovered the green tree frogs’ solution to the so-called cocktail party problem.

Frog physics: The May 2021 issue isn’t the first time frogs have been featured in the pages of Physics Today: Find out why the polka-dot tree frog fluoresces when exposed to UV light and how the aquatic clawed frog uses acoustics to find insects . Retinal photoreceptors taken from the eyes of the same species of clawed frog were used to demonstrate that such cells can detect single photons .

Cover design: Other candidates for this issue’s cover included images of salt flats, inspired by the story about the global lithium supply on page 20 . But the editorial and art teams unanimously agreed on the curious-looking red-eyed tree frog on a clean, striking background. The first draft’s font (below left) was underwhelming next to the dominating image. The solution: Didoni , a font whose curly serifs on a few of its letters resemble the shape of the frog’s fingers and toes (right).

Photo by iStock.com/alptraum