Input E · SCIENCE ARTICLE — DISCOVERY OF AN URBAN FROG SPECIES

THE FROG WITH THE TWO-PART CALL

A frog first noticed in a noisy transport corridor was separated from its look-alikes by combining sound, appearance and DNA evidence.

A

Researchers monitoring wildlife in a dense city district placed automatic recorders beside six shallow garden pools built under an elevated railway. They expected to hear two common frog species already known from nearby parks. Instead, several night recordings contained a repeated two-part call that did not match either species.

B

At first the team considered whether traffic noise was changing the call, so they recorded frogs at the pools and at a quieter botanical garden. The unusual call kept the same two-part pattern in both places, suggesting noise was not creating it. Close photographs also showed a narrow bronze line behind the eye that the common species lacked.

C

Researchers then collected tiny skin swabs for DNA analysis and compared the results with museum samples of related frogs. The genetic pattern formed a separate group, supporting the evidence from calls and appearance, and the separation remained clear across samples collected on different nights. A four-week survey found that most adults used the smallest pools only after heavy evening rain.

Survey record	Call	Eye mark	Typical survey site
Candidate frog	Two-note call	Bronze line behind eye	Small rain-filled pools
Common garden frog	Single repeated note	No bronze eye line	Deeper permanent ponds

D

The finding changed how maintenance crews treated the garden pools. Because the frogs bred after heavy rain, scheduled cleaning was moved away from the wettest weeks, and one pool was left partly untrimmed for cover. The case shows why urban biodiversity surveys are stronger when different kinds of evidence point to the same conclusion.

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