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Tink frog calls allow researchers to measure population

Given their often tiny size and cryptic nature, how does one determine frog populations in the rainforest? Just eavesdrop. A new study in’s open access journal Tropical Conservation Society (TCS) employed automated recorders to listen to amphibian calls to determine if the common tink frog (Diasporus diastema) could be found in recovering secondary forests in Costa Rica.

“[The common tink frog’s] small size and its preference for calling from hidden sites make it difficult to observe in the field. In contrast, its ‘tink’ call is loud and easily differentiated from other species,” the researchers write.

A brown bear in Alaska. Photo by: Rhett A. Butler.
A brown bear in Alaska. Photo by: Rhett A. Butler.

Gathering 49,273 recordings from 12 secondary forests and 3 primary forests, the researchers noted the tink frog’s distinct call in about 21 percent of the total recordings (10,605). Surprisingly, they found no change in the number of tink frog’s calls in primary forest over secondary forest.

“Given that the secondary forests were abandoned pastures, and [the tink frog] has been reported as a forest species, it appears that the species has recovered rapidly in these sites,” the researchers write. Their study contrasts with earlier research that failed to find the tink frog in secondary forest, however the scientists note that in the previous study “a large river separated the mature and secondary forest, which may have limited colonization.”

The scientists did find that calling changed depending on the season and time. Peak calling occurred from 10 PM to 1 AM, and calling was very low during the dry season.

The researchers conclude that “given the extent of amphibian decline, there is a small glimpse of hope that these secondary forests can help maintain populations of this and other amphibians.”

CITATION: Hilje, B. and Aide, T. M. 2012. Calling activity of the common tink frog (Diasporus diastema) (Eleutherodactylidae) in secondary forests of the Caribbean of Costa Rica. Tropical Conservation Science Vol. 5(1):25-37.

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