This species occurs in the Departments of Junín and Pasco, Peru. It has been recorded in Lake Junín and surrounding tributaries in the Junín National Reserve and Historical Sanctuary of Chacamarca, and tributaries to the Mantaro River in the National Sanctuary of Huayllay, Pasco. Between 2010 and 2011, attempts were made by the Regional Government of Junín to introduce this species into the upper Mantaro valley, in the central Andes of Junín, however its occurrence there is currently unknown and needs to be verified with surveys (O.J. Damian Baldeón pers. comm. February 2018). Within its native distribution, it has an elevational range of 4,000–4,600 m asl. Its extent of occurrence (EOO) is estimated to be 1,118 km2 and all individuals are considered to occur in less than five threat-defined locations.
Habitat and Ecology
It is an exclusively aquatic species. It is restricted to marshy lakes, such as Lake Junín, smaller, deep, isolated lakes, as well as, streams, rivers, wetlands, and canals around Lake Junín (A. Watson and A. Fitzgerald pers. comm. February 2018). Ideal stream habitat characteristics of this frog are free of predatory, invasive rainbow trout with moderate levels of silt and relatively clean water (Watson 2017a). It reproduces by larval development. Tadpoles prefer microhabitats characterized with a silt-like substrate, depths of more than 30 cm, low currents, presence of native fish (Orestias spp.), and submerged vegetation (Castillo 2017). In a study on diet composition and prey selection, Watson et al. (2017b) found that the Junín Giant Frog appeared to select snails (family Physidae) and mayflies (family Baetidae) from the available prey in the environment.
Previously common, this species has undergone a noticeable decline over the last thirty years. In 1996, there was a mass die-off in Lake Junín and other water bodies of the Sierra Central, the cause of which is still uncertain (Becerra Díaz 2012).
While current population estimates are not available, the population is suspected to be decreasing due to ongoing decline in the quality and extent of its habitat, and there is continuing decline in mature individuals due to overexploitation. Linear transects and diving surveys in lagoons, rivers, streams, and channels in and around Lake Junín during October to December 2012 detected 12 individuals, however the species was present in only 10.76% of the 65 surveyed sites (Loza Del Carpio and Mendoza Quispe 2017). During monthly surveys in three protected areas in Junín and Pasco between January 2015 and July 2016, adults and/or tadpoles were found in only eight out of twenty sites (Watson et al. 2017b).
The species appears to be restricted to water bodies with good water quality, and has not been recorded during recent surveys in the northern zone of Lake Junín where there are signs of contamination (Loza Del Carpio and Mendoza Quispe 2017). According to surveys of local inhabitants in 2012, 95% of interviewees stated that they had directly observed this frog in their natural habitats at some point, however 65% indicated that they last saw the frogs more than six years ago and only 10% saw this species as recent as in 2012 (Loza Del Carpio and Mendoza Quispe 2017).
The species is generally threatened by introduction of trout into lakes, streams, and rivers in the high Andes, disappearance of native fish of the genus Orestias, uncontrolled exploitation as a food source, emerging infectious diseases (chytridiomycosis and ranavirus), climate change, and loss of habitat through the extraction of resources, agricultural, industrial, and residential pollution, eutrophication, over-grazing by livestock, and fluctuations in water levels controlled by the Upamayo dam (Watson et al. 2017a,b). The cleaning of channelised streams, which involves the periodic removal of submerged aquatic vegetation and sediment, represents an additional threat to the species and its habitat (L. Castillo Roque pers. comm. February 2018). Large amounts of acid mine drainage and heavy metals, such as copper, zinc and lead, from the Cerro de Pasco region are discharged into the lake, and its surrounding lagoons and wetlands via the San Juan River, the lake's main tributary (Rodbell et al. 2014, Watson et al. 2017b). This is particularly damaging to this frog, due to its high sensitivity to contaminants and the high permeability of its skin.
Congeners in southern Peru have been infected with chytrid (Seimon et al. 2005, Catenazzi et al. 2011), and one species in nearby Ecuador has disappeared, suggesting this species might also be at risk. In 2014, 14 samples tested negative for the presence of Batrachochytrium dendrobatidis (R. Elias pers. comm. March 2018), and there are no reports of the species being infected with this fungus as of yet (A. Catenazzi pers. comm. April 2017).
This species occurs in the Junín National Reserve, the Historic Sanctuary of Chacamarca, and the National Sanctuary of Huayllay (Watson et al. 2017b). An in situ frog monitoring and conservation education program called the “High-Andean Frog Conservation through Capacity-Building Program” funded by USAID Small Project Assistance grants was in place from 2014–2016 (S. Behmke pers. comm. April 2016). Since then, conservation, citizen science, and environmental education efforts have been initiated by a local NGO, Grupo RANA (Respuestas y Acciones para la Naturaleza y sus Amenazas; L. Castillo Roque and O.J. Damian Baldeón pers. comm. February 2018). In October 2016, a second workshop was held in Junín Municipality to establish a conservation strategy for the frogs of Junín (Telmatobius brachydactylus and T. macrostomus), and a conservation action plan was developed (Watson et al. 2016, A. Watson pers. comm. February 2018). In the past, attempts at captive breeding of this species have been made; however, the breeding centers around Junín National Reserve were closed in 2012 (Coronel and Rojas 2014, Watson et al. 2017a). In 2018, Huachipa Zoo will start a captive breeding programme with support of Amphibian Ark Seed Grant (R. Elias pers. comm. March 2018).
This species is listed as Endangered (EN) in Peru and has legal protection provided by the Categorization in Endangered Species of Wild Fauna (Decreto Supremo Nº004-2014-MINAGRI), which bans all hunting, capture, possession, transport or export of the species for commercial purposes.
Measures are urgently required to control and manage the harvesting of this species from the wild and limit the impact of invasive trout on native fauna of the lake. The conservation and protection of Lake Junín’s surrounding rivers, streams, wetlands, and lagoons are of utmost importance. Watson et al. 2017a have identified these bodies of water as critical habitat for the conservation of the species considering that the influx of metals to Lake Junín will continue until efforts are focused on preventing these sediments from entering the lake.
More information is needed about this species' distribution, population status, life history, harvest levels, and threats. Additional studies on the food habits of introduced rainbow trout and comparison with this frog is needed (Watson et al. 2017b). Continued long-term monitoring is needed to inform appropriate conservation management of this threatened, high-elevation, endemic species (Watson et al. 2017a, Castillo 2017). Further studies should monitor trends in harvest levels, population demographics, the presence of emerging infectious diseases, and microhabitat utilization.
Red List Status
Listed as Endangered because of its extent of occurrence (EOO) of 1,118 km2, it occurs in less than five threat-defined locations, there is continuing decline in the area and quality of its habitat caused primarily by water pollution and siltation, and a continuing decline in the number of mature individuals due to uncontrolled exploitation as a food source.
IUCN SSC Amphibian Specialist Group 2018. Telmatobius macrostomus. The IUCN Red List of Threatened Species 2018: e.T2645A89195689. http://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T2645A89195689.en .Downloaded on 16 January 2019