This species is a high-altitude montane anuran, usually occurring between 1,600–3,400 m asl, and is endemic to southern Africa and Lesotho. It occurs in the Afro Mountain Grassland and Alti Mountain Grassland areas and is found in most of the major rivers of Lesotho, as well as in the upper reaches of tributaries of the Thukela and Mzimkulu rivers in the Drakensberg of KwaZulu-Natal, the Elands River in the Free State, and the Bell River in the Eastern Cape.
Habitat and Ecology
It is a water-dependent species in montane grassland. The adults are largely aquatic, preferring cold, clear mountain streams with rocky substrates (Lambiris 1991). They are able to remain completely submerged for long periods, and have been observed to spend up to 30 hours under water (Bush 1952), while tadpoles and juveniles spend more time closer to the surface and in shallower pools (Bates 2004). During the winter months both adults and tadpoles have been observed swimming under the ice that frequently forms a layer on the rivers in the highlands.
Although they are found most commonly where conditions are classified as pristine, large numbers have observed in the Sani River near the Lesotho border post, the water of which is quite polluted from the laundry activities and debris from the nearby village. Breeding occurs during the warmer months (September–February), with males calling from under the water or with just the head protruding. Eggs are laid in large, sticky clutches in slow-flowing water and become attached to sunken vegetation (Bates 2004).
It is locally abundant across its range throughout eastern and central Lesotho. Subpopulations in Silaka Nature Reserve, near Port St. Johns in the Eastern Cape, occur in abundance (Venter and Conradie 2015). It may have experienced local declines as a result of damming of major rivers for the Katse and Mohale dams. Concerns have previously been raised over recorded pathogen-related mortalities (Smith et al. 2007), although the effect on this species is as yet unknown.
It is not significantly threatened because of the remoteness of its habitat. Local populations are probably affected by afforestation, dam building, and overgrazing by livestock, especially sheep, causing erosion and subsequent siltation of rivers. It is used in local traditional medicine for treating burns, but probably not at a level to constitute a threat to the species. Populations have been found to be infected by Batrachochytrium dendrobatidis, which causes chytridiomycosis. This frog has the ecological characteristics of a species that is potentially at risk from chytridiomycosis, and so its populations should be regularly monitored (there has already been one recorded die-off, but this was not confirmed to be a result of chytridiomycosis).
It could also be potentially threatened in areas of Lesotho affected by the Lesotho Highlands Water Project, where the filling of the Katse and Mohale Dams may have resulted in habitat loss, as well as, the isolation and even extinction of some populations (Bates 2002, Minter et al. 2004). An additional observed risk to both species is the threat of predation and competition posed by the introduction of trout and other alien fish for recreational fishing into the main rivers of Lesotho (Swartz 2005). In heavily stocked regions it is common that the frog species only occurs in smaller rivers and tributaries not accessible to trout, for example, where above waterfalls, which inhibit the movement of trout.
The species has a relatively restricted range and is endemic to the Lesotho and Drakensberg highlands. It occurs, and is therefore protected, in the following nature reserves in South Africa: Cathedral Peak, Drakensberg Gardens, Giant’s Castle Game Reserve and the Royal Natal National Park. In Lesotho it occurs in Ts’ehlanyane National Park, Sehlabathebe National Park and the Bokong Nature Reserve. It also occurs in uKhahlamba Drakensberg Park and rivers in the Maloti Drakensberg Transfrontier Park between Sehlabathebe and the uKhahlamba Drakensberg Park World Heritage Site (Bates 2002).
This species would benefit from monitoring of subpopulations with particular reference to the spread and effect of chytrid. Base line data on life-history, ecology, population trends and threats are all required before monitoring can begin.
Red List Status
Least Concern (LC)
The species is Least Concern due to its relatively wide distribution across its range and apparent abundance at sites at which it occurs. However, the population as a whole is likely to have experienced declines as a result of the damming of major rivers in Lesotho as part of the Lesotho Highlands Water Project, as well as, recent road construction projects, resulting in local impacts on river habitat. It does appear to tolerate some habitat modification in the form of eutrophication.
This species has a confusing taxonomic history which has been reviewed several times (Tarrant et al. 2008, Channing 2015). Most recently known as Amietia umbraculata, Channing (2015) reverted the name to A. vertebralis based on examination of type specimens and Zoological Nomenclature rules.
IUCN SSC Amphibian Specialist Group & South African Frog Re-assessment Group (SA-FRoG) 2016. Amietia vertebralis. The IUCN Red List of Threatened Species 2016: e.T54359A113299791. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T54359A77158948.en .Downloaded on 14 December 2018