Arthroleptella rugosa is a very small frog species, with adult individuals typically reaching a length of just 12 to 15 mm. The Rough Moss Frog exhibits cryptic coloration that blends seamlessly into its black-soil wetland habitat. Its dorsal surface ranges from dark brown to olive green, often with irregular dark patches or mottling, which provide effective camouflage among grass tussocks, moss, and soil. True to its common name, the Rough Moss Frog has a notably rough, granular skin texture on its dorsal side. This rugged texture, combined with its coloration, makes it resemble moss or rough soil, aiding in its concealment. Its ventral side, in contrast, is smoother and lighter in colour, often displaying pale, off-white or light grey tones.
The limbs of Arthroleptella rugosa are slender but well-adapted to its environment. Its fingers and toes are relatively short, with no webbing, as the species does not rely on swimming. Instead, the limbs are suited for movement across the damp, moss-covered surfaces of its montane habitat.
In 2006, Dr. Andrew A. Turner of Cape Nature and a team of researchers discovered and formally described this species, which is endemic to the Klein Swartberg Mountain. They drew attention to its highly restricted distribution on the mountain and its urgent conservation needs.

Breeding Habits
The Rough Moss Frog breeds during the wet winter months, generally from May to August, when seasonal rains temporarily increase moisture in its montane environment. These rains create shallow pools or wet, mossy areas essential for breeding. Males call during the daytime, producing a series of short, high-pitched chirps to attract females. The males select moist areas near their breeding sites to call.
After mating, females lay their eggs on moist surfaces, such as grass tufts, near or in shallow water. The species exhibits direct development, meaning the eggs bypass the tadpole stage entirely, with froglets hatching fully formed. This is a significant adaptation to life in a region prone to droughts.
Habitat and Conservation Efforts
The Rough Moss Frog is found exclusively on the Klein Swartberg Mountain, an inselberg mountain solidly rising amidst extensive agricultural development in South Africa’s Overberg region. Before 2019, only three populations of this species were known on the mountain. Surveys and monitoring revealed a decline in these populations due to the encroachment of alien invasive vegetation, particularly pine trees, which threaten the remaining habitat.
Since 2019, Bionerds has been implementing conservation measures for the Endangered Wildlife Trust (EWT). The EWT’s Western Cape Threatened Amphibian Programme (WC TAP) has included the Rough Moss Frog as a species of concern, with primary threats being habitat loss from invasive plants and too-frequent, unplanned fires. These pressures have contributed to a marked population decline and included in the IUCN Red List, 2016.
During surveys in May 2020, researchers observed a significant encroachment of alien vegetation threatening to engulf the remaining frog populations. It became clear that rapid intervention was needed to protect and restore these critical habitats. However, efforts were delayed by the Covid-19 pandemic.
In 2021, the project received a rapid action grant from the IUCN Save Our Species initiative and the European Union. The grant was used to create a firebreak around the Rough Moss Frog populations. Time was of the essence, as pine trees in the area were beginning to cone, and delaying intervention risked seed dispersal. In March 2022, a controlled ecological burn was undertaken by the Klein Swartberg Conservancy – the first time globally that fire was used as a management tool to protect a frog species from extinction.
The controlled burn was managed for the Klein Swartberg Conservancy by the Overberg District Municipality’s Fire Department and the Greater Overberg Fire Protection Association. Despite unforeseen weather conditions causing the fire to spread beyond the planned area, the burn in the targeted region was successful. When researchers returned 4 months later in July 2022, they were relieved to hear Rough Moss Frogs calling at all known populations. Subsequent surveys even uncovered new populations, a major success for the project and the species.
Long-term Monitoring
From July to September 2023, during the coldest and wettest months of the year—the Rough Moss Frog’s breeding season, acoustic surveys were conducted to determine the presence or absence of the frogs at all known sites. Using three-unit audio recorders deployed for roughly an hour at each site, scientists recorded frog calls to assess population sizes. These surveys will continue annually for five years to evaluate the effectiveness of the controlled burn in preserving the habitat and to track the recovery of the frog populations.
The landowners involved in the Klein Swartberg Conservancy are committed to protecting this species. An alien vegetation clearing plan has been developed, aiming to remove invasive plants from the mountain over the next decade.