Rana subaquavocalis: The Rarest Frog in the U.S.
According to Platz, the next steps are to determine how vulnerable this species is to extinction. They are known to live in two places. There are about 45 individuals living in Ramsey Canyon and about 55 living in nearby Brown Canyon.
The frog is green and olive-brown in coloration and about 6 inches in length. Some of the individuals were at least 10 years old, about twice the age that most leopard frogs get. By the way, the age of frogs is determined by counting the annual rings found in the toe bones.
The professor believes that the frogs were quite common about 17,000 years ago when glaciers covered most of the country and the climate was much cooler. As the glaciers retreated, the climate became hotter and dryer forcing the frogs to move to mountain streams. The frogs at the low altitudes perished but those who made it to the mountains survived. They were isolated from the gene pool of other leopard frogs for several thousands of years and eventually became a new species.
Platz returned to the area in 1989 equipped with a tape recorder and hydrophones. He found several egg masses, which indicated that the frogs were breeding. However, one important factor was missing - there were no vocalizations. He placed the hydrophone in the water and was greeted by a plethora of frog calls. So why would frogs call from underwater? Platz offered these hypotheses: 1) a frog calling at the edge of the pond maybe heard by a predator and thus placed at disadvantage; 2) sounds emitted underwater travels much farther than on land, giving males a better opportunity to attract a mate; 3) frogs would avoid the cooler evening temperatures, since water cools more slowly than land; and 4) the frogs can begin their breeding season earlier in the year giving tadpoles time to grow up and prepare for winter.
In 1995, Platz and other conservationists have been trying to increase the population of these frogs by collecting eggs and raising the tadpoles in large horse tanks for later reintroduction. Also, efforts to improve the habitat of the area are being planned. The frogs live in canyon ponds within the Nature Conservancy¹s Ramsey Canyon Preserve. As more people became involved in the project, a third population of the frogs was discovered. Dr. Platz is working with the conservancy, the ranch owner, the U.S. and Arizona fish and game departments, and the military to draft a recovery plan for the frog. The U.S. Army is involved because Ramsey Canyon borders a large military reservation. The plan also calls for the eventual establishment of 8 population groups that are close enough so the frog can migrate from place to place.
The Nature Conservancy has a detailed article about Rana subaquavocalis
in the September/October 1997 issue of Nature Conservancy. The article
"The Naked Frog" by William Stolzenburg can be read online at:
Omaha World-Herald, "Frog Lover Happens Onto Hoppers", October 9, 1993
Omaha World-Herald, "Frog Man Has Found New But Dying Species",
July 14, 1995