The Herpetological Journal

DOI: https://doi.org/10.33256/36.2.8797

pp. 87-97

Authors: Rebecca De Salem E. Fanomezantsoa, Nirhy H.C. Rabibisoa, Sam Hyde Roberts & Devin A. Edmonds

Abstract: Amphibians are among the most threatened vertebrates, yet many species lack the ecological and demographic data needed to implement effective conservation measures, especially in tropical regions. William’s bright-eyed frog Boophis williamsi is one of Madagascar’s most highly threatened frog species, being restricted to a small area of the Ankaratra Massif in the central highlands. We conducted fieldwork during 2018, 2019 and 2021 to identify habitat associations across life stages and estimate abundance along ten stream transects. Our results confirmed B. williamsi presence at seven localities within a small area of only a few square kilometres, the only location the species is known to occur. Habitat associations varied by life stage, with tadpoles more often found in shaded, rocky streams within humid montane forest, while adults were more often found along rocky streams in open savanna habitats. Overall, streams were shallow (0.18–0.83 m), cool (7.70–17.80 °C), and often slightly alkaline (pH 6.70–8.26). Using N-mixture models, we estimated fewer than 600 individuals (tadpoles and frogs combined) across four surveyed stream transects during the 2018–2019 austral summer. Detection probabilities for frogs were seasonally variable, peaking in December at the onset of the rainy season. Conversely, tadpoles had higher and relatively constant detectability across September, December and March. Despite ongoing threats from deforestation and fire, B. williamsi persists at Ankaratra, likely aided by recent conservation efforts. We recommend the development of a standardised, long-term monitoring protocol incorporating both tadpoles and frogs, as well as increased protection of high-elevation forests near stream habitats that support this imperilled species.

Keywords: amphibian conservation, Ankaratra, biodiversity conservation, detection probability, range-restricted species