Frogs and Toads Exhibit Diverse Vocal Sac Evolution

As a University of Florida study reveals, frogs and toads have evolved one amazing diversity of sonic sacs. Indeed, researchers found 20 different types of these structures. Herpetologists Agustín Elías-Costa and Julián Faivovich have spent more than ten years researching the discovery. In total, they visited over 777 specimens across the globe, with significant trips to physical museums including the Smithsonian’s National Museum of Natural History in Washington, D.C.

Elías-Costa, affiliated with the Bernardino Rivadavia Natural Science Museum in Buenos Aires, alongside Faivovich, explored the evolutionary significance of these vocal sacs. Their results emphasize that vocal sacs are only found in about half of the 4,358 species. In addition, lead author Dr. Daniele Germano found that about 18 percent of the species studied lack vocal sacs entirely.

Elías-Costa expressed surprise at the extent of their findings, noting, “that’s actually only half the species of frogs.” He emphasized the biological importance of these structures, stating, “an astounding number considering their biological importance.”

The study reports that vocal sacs have disappeared between 146 and 196 times throughout the evolutionary history of frogs and toads. This beautiful thing further highlights the ongoing process of change in this amazing animal family. Male frogs and toads use their inflatable vocal pouches (or sacs) to project their croaks. These calls are essential for reproduction and social structures.

The scientists recorded plenty of other interesting and different shapes of vocal sacs in other species. For example, male frogs develop inflation sacs that look like ballooned-out, khaki-colored Mickey Mouse ears. Others, like the male Indian bullfrog, exhibit vibrant blue vocal sacs that swell during calls. To top it off, as noted by the new study, the male Surinam goldeneye tree frog has these weird paired head-side sacs that expand during calls.

These innovative adaptations help facilitate clear communication within diverse communities of amphibians. They point out the amazing evolutionary smarts of these species. Elías-Costa and Faivovich reported their findings in the Bulletin of the American Museum of Natural History. Their results have significantly advanced our knowledge of amphibian biology.