Introducing the Rough Moss Frog

The Rough Moss frog is a unique little frog, actually a minusculefrog, with a body length in adult males of only 15 mm and a couple of extra millimetres in females. This tiny frog went unnoticed by science until its discovery by Michael Cunningham and Kate Hendersen in 2004 and it was formally described as a new species in 2008 by the author and Professor, Alan Channing, of the University of the Western Cape. Another feature that makes it unique is that it occurs on only one mountain, near the Overberg town of Caledon. This sandstone mountain has been isolated from other Fynbos-clad sandstone mountains for millions of years (by the intervening shales) and has led to the evolution of the Rough Moss frog which looks and sounds different to all the other Moss frogs.

Its imperilled habitat

For anyone who has travelled on the N2 past Caledon, it is hard not to notice the jungle of invasive alien trees that have taken over much of the little mountain to the north of the highway. There is an incredibly dense infestation of wattles, eucalypts and, over much of the mountain, Mediterranean cluster pines. Invasive alien trees such as these have dramatic effects on the ecosystems: outcompeting the indigenous Fynbos, sucking up excessive amounts of water and changing the way fire behaves, by providing much more fuel. Fires are crucial components of fynbos ecosystems, but fires in dense invasive alien tree stands are much more serious and difficult to control and can lead to lasting damage to indigenous seed stores and even soil structure. For a frog that is dependent on permanently moist habitats, having invasive alien trees that use much of this precious water and contribute to desiccating fires, is a threatening situation and occurring on only one mountain makes this situation all the more risky. Taking these and relevant facts about their biology into consideration, this frog is Critically Endangered and in need of urgent attention.

Plans for recovery

Fortunately, this frog and its special habitat (also hosting several plant species of conservation concern) are no longer unnoticed. Plans have been made to manage the Klein Swartberg Conservancy, especially the Rough Moss frog habitat. As part of a cooperative effort between the Klein Swartberg Conservancy, the Endangered Wildlife Trust, Bionerds, the Fynbos Trust and CapeNature, a strategy to use planned fire to control the now seriously dense and rapidly worsening pine invasion, has been set up. Fire is both an enemy and friend to the moss frog. Fire is needed to maintain the fynbos vegetation, but when fires are too frequent or severe, as happens in dense alien tree invasions, then the frogs struggle to retain sufficient population sizes for long-term persistence. However, if we protect critical breeding habitat and reduce pines with judicious, well planned and executed ecological burns, then the natural habitat can be restored and maintained. Key to being able to do this were the new populations found in uninvaded areas by the Bionerds, which provides rescue populations from which the invasive alien or fire-impacted populations may recover.

Funding and action

Not only have the plans been made, but they are being put into action. This has not been easy with the advent of the COVID-19 pandemic, which slowed down the actions required. Luckily funding was obtained to assist the Conservancy to implement the suite of fire breaks and ecological burns to push back the pine invasions and secure the Rough Moss frog habitat. The fire breaks have been created and the burning is set to happen by May 2022. This will be followed by monitoring to evaluate the success of these actions by CapeNature and Stellenbosch University with surveillance by the Endangered Wildlife Trust. For this monitoring, break-through technology is employed that allows a rigorous estimation of the numbers of calling males using an array of microphones and the application of Acoustic Spatially Explicit Capture-Recapture statistics.

In addition to urgently required control of invasive alien plants, three of the properties holding critical Rough Moss frog habitat have just been approved for Contract Nature Reserve status under the CapeNature Stewardship Programme, further securing this threatened frog and its habitat. This is a great example of where a flagship species has spearheaded a conservation effort, even if the flagship is a tiny frog!