On Land: Amphibians
Lesser Antillean whistling frog
Eleutherodactylus johnstonei
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About
These tiny-but-mighty frogs dominate Saba’s nighttime soundscape — as soon as the sun begins to set, a chorus of their lilting, two-note whistles begin to rise from bushes and trees all around the island. Spotting them, however, is a little harder: They measure no more than about 3 cm/1 inch in length, and their brown coloration helps them blend seamlessly into vegetation in their tropical habitats.
Their melodious chirps serve many purposes, including attracting potential mates and establishing territory. Their two-note call can be repeated up to 60 times per minute, and researchers continue to study what various chirp-frequencies may be communicating to other frogs.
Unlike many amphibians, the Lesser Antillean whistling frog doesn’t have a free-swimming tadpole life-stage. Instead, adult frogs lay their eggs in leaf litter or other moist environments, and the young hatch as “froglets,” looking essentially the same as their adult counterparts (with the addition of a short, stumpy tail that disappears within a single day). This unique life-cycle could be one reason they’re thriving across the Lesser Antilles — without a free-swimming tadpole stage, even moist undergrowth makes for a suitable egg-environment.
In 2022, research from the California Academy of Sciences and other partners showed that Lesser Antillean whistling frogs are actually native to the island of Montserrat, and were introduced across other islands, including Saba, long ago (likely by acting as stowaways on trade vessels; read more in the “Ask a Scientist” module at the bottom of this page). Scientists are still working to discern whether these little frogs are outcompeting native frogs on islands where they’ve been introduced, and you can help: Snapping photos of these frogs and uploading them to iNaturalist helps researchers map where populations exist, which brings us one step closer to understanding the species’ impacts on Saba’s ecosystem. And if you’re having trouble capturing a photo of these tiny amphibians, you can always upload a recording of their lovely songs instead!
Header image by @michaelbakkerpaiva (CC-BY).
Credit: @arkantor, iNaturalist (CC-BY-NC-SA).
iNaturalist Observations
Where locals, researchers, and visitors have seen this species.
Google / Imagery © 2023 CNES / Airbus, Landsat / Copernicus, Maxar Technologies, U.S. Geological Survey, iNaturalist Map data @2023
This map shows geotagged observations of this species made on iNaturalist, the world’s largest community-science platform.
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Ask a Scientist
Question: How did you determine that this species is native to Montserrat, and was only later introduced to Saba?
Answer: Genetic tools allow us to infer the last time frogs on a particular island shared a common ancestor. On Montserrat, the last common ancestor of modern frogs lived between 240,000 and 810,000 years ago, a time that predates human habitation (which started only ~8,500 years ago). But on every other island, including Saba, these frogs all share a common ancestor that overlaps with human settlement. This supports the finding that the frogs likely evolved on Montserrat, then were spread by humans to other islands in the region.
Dr. Michael Yuan
Herpetologist and researcher with the Islands 2030 initiative, California Academy of Sciences
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