RRI.CO.ID, Cibinong - Researchers from Indonesia's National Research and Innovation Agency (BRIN) have discovered a new species of bush frog (also commonly known as shrub frog), Philautus candrageni, on the slopes of Mount Merapi in Yogyakarta. The discovery brings the number of known endemic Philautus species on Java to four, up from three previously recorded.

The discovery was made by a research team from BRIN's Research Center for Biosystematics and Evolution, led by Alamsyah Elang Nusa Herlambang, along with several collaborators. The study was based on intensive field surveys conducted across Central Java and the Special Region of Yogyakarta between 2017 and 2025, as well as examinations of specimens housed at the Museum Zoologicum Bogoriense (MZB), managed by BRIN's Directorate of Scientific Collection Management.

The findings identify Philautus candrageni as a previously unknown bush frog species from the Mount Merapi area. The discovery increases the number of endemic Philautus species known from Java from three to four.

The research also clarified the taxonomic status of the endangered Philautus jacobsoni, which had long been known from only a handful of records. The species had even been regarded as a "lost species" because it had not been observed for an extended period.

Alamsyah further said newly described frog is distinguished from its closest relatives by a combination of morphological, genetic, and bioacoustic characteristics.

"Philautus candrageni has a medium-sized body, a distinct canthus rostralis, relatively smooth dorsal skin, and a unique advertisement call consisting of three different notes," he said, as quoted from the official press release from BRIN on Saturday, July 4, 2026.

The team identified the new species using an integrative taxonomic approach that combined morphological examination, molecular phylogenetic analysis based on mitochondrial DNA, and bioacoustic analysis of mating calls. This multidisciplinary method enabled researchers to identify an evolutionary lineage that had previously remained hidden, a phenomenon known as cryptic diversity.

Researchers found that Philautus candrageni has a restricted distribution, occurring only on the slopes of Mount Merapi, where it inhabits plantations and mid-elevation mountainous environments. Researchers suggested naming the new species as "Merapi Bush Frog" or in Indonesia "Katak-semak Merapi."

Alamsyah warned that endemic species with limited geographic ranges are especially vulnerable to environmental change, including habitat degradation caused by human activities and ecosystem shifts in mountain regions.

"More targeted conservation efforts are needed to protect the natural habitats of endemic species and ensure that their populations can persist in the wild," he said, as quoted by the press release.

A bush frog (also commonly known as shrub frog) is a small frog that typically inhabits shrubs, bushes, and other low vegetation in forests and mountainous areas. It is generally identified by its compact body, expanded toe pads for climbing, and distinctive mating calls, which are often used by scientists to distinguish closely related species.