Ecology and demography of the Critically Endangered Kandian torrent toadAdenomus kandianus: a long-lost endemic species of Sri Lanka

Abstract

The tropical island nation of Sri Lanka is a biodiversity hotspot with a high diversity and endemism of amphibians. The endemic, stream-dwelling Kandian torrent toadAdenomus kandianusis Critically Endangered and was considered to be extinct until its rediscovery in 2012. The species is now known from two localities in tropical montane forests. We conducted a 4-year study using transect surveys and opportunistic excursions to assess habitat associations, demographics and abundance ofA. kandianusin and around Pidurutalagala Conservation Forest. We recorded a mean of 44.25 post-metamorphs per year, with a density of < 1 individual per 100 m2, with occurrence within a narrow extent (c. 0.005 km2) of the stream channel. Behaviour and microhabitat selection varied depending on sex and stage of maturity. The species preferred moderately sized montane streams with rocky substrates and woody debris, colder temperatures, and closed-canopy, intact riparian forests. We noted size-based reversed sexual dimorphism and a strong ontogenetic relationship between snout–vent length and body weight. Anthropogenic activities such as intensive crop farming deterred the species; proximity to croplands had a negative influence on abundance. We recommend re-delineation of the boundary of Pidurutalagala Conservation Forest to incorporate the toad's habitat into the core of the reserve and thus limit the impacts of human activities. Conservation and management actions such as ex-situ breeding, population monitoring, and restoration of degraded habitats could also contribute towards the persistence of this toad. Our findings provide useful insights into ecological research on and conservation of range-restricted aquatic amphibians.

A review of amphibian fauna of Sri Lanka: distribution, recent taxonomic changes and conservation

“…Most of the endangered and threatened amphibian species are restricted to the forests (some even fragmented) within the highly populous districts like Galle, Kalutara, Kandy, Matara, and Nuwaraeliya. Due to increase in infrastructure in these highly populous areas, more destruction occurs, e.g., clearing of wetland vegetation and forest borders/ buffer zones (Karunarathna et al, 2016). Thus, the forest reserves/ wetlands are fragmenting.…”

“…This project can be used as a base study for the future conservation programs for the other related threatened species, viz., Uperodon palmatus with similar behavior. Recently, ecology and demography of Adenomus kandianus were assessed in the Peak Wilderness (Karunarathna et al, 2016). Karunarathna et al (2016) mentioned the need for further studies to assess their breeding biology and population viability.…”

“…Recently, ecology and demography of Adenomus kandianus were assessed in the Peak Wilderness (Karunarathna et al, 2016). Karunarathna et al (2016) mentioned the need for further studies to assess their breeding biology and population viability. Also, Janzen and Bopage (2011) stated that there is a lack of studies on the distribution and ecology of amphibians in Sri Lanka.…”

Morphometry and habitat selection of the Mountain Hourglass Treefrog [<em>Taruga eques</em> (Günther, 1858)] (Amphibia, Rhacophoridae) in the Horton Plains National Park, Sri Lanka

“…feeding on amphibian eggs. Hence, it is very important to take conservation action on species such as the narrow-ranging endangered frogs in Sri Lanka including the critically endangered Kandyan Torrent Toad (Adenomas kandiaunus) (Karunarathna et al, 2017a).…”

“…Activities for active searching included examining leaf litter on trees and tree trunks, understory vegetation, turning rocks, and moving some movable debris (Karunarathna et al, 2017a). Water pools were sampled using the same transects for the foam nest counting.…”