By Risidra Mendis
A small toad believed to be extinct and not spotted since 1876 was rediscovered by a group of scientists at the Peak Wilderness Sanctuary.
The Kandyan Dwarf toad, Adenomus kandianus (Günther, 1872) was first recorded in 1872 and then vanished for over a century before been accidently found by the group of scientists in 2009.
The genus Adenomus is endemic (only found in Sri Lanka) to Sri Lanka and comprises of only three species.
The Sri Lankan endemic (only found in Sri Lanka) genus Adenomus is represented by the three species Adenomus. dasi, Adenomus. kandianus, and Adenomus. kelaarti all of which are stream dwelling toads.
The World Conservation Union (IUCN) had also listed this toad species as extinct prior to it been rediscovered.
“It’s most likely that this population will be categorised as a Critically Endangered (CR) population in future updates of the IUCN Red List of Threatened Species says Herpetological Foundation of Sri Lanka (HFS) President L. J. Mendis Wickramasinghe.
The rediscovery of the Kandyan Dwarf toad was recorded in the journal Zootaxa by the HFS Mendis, Dulan Ranga Vidanapathirna and Nethu Wickramasinghe.
But despite this rare and unusual discovery of the toad in one of Sri Lanka’s largest natural reserves, scientists warn that the toad may be in danger of becoming extinct, due to tree-felling to make way for tea cultivation and illegal gem mining that threaten the toad’s forest habitat.
Pollution caused by the millions of pilgrims who flock to the nearby Sri Pada mountain each year could also pose a threat to the survival of the Adenomus kandianus.
Speaking to Ceylon Today Mendis said the Peak Wilderness Sanctuary is rich in bio diversity and should be protected if the remaining toad species is to be saved from extinction.
“This sanctuary is home to many other important varieties of birds and amphibians. All 26 endemic bird species can be seen in the Adam’s Peak (Sri Pada) area,” Mendis explained.
The scientists who rediscovered the Kandyan Dwarf toad explain that they came across it during a night-time sampling session on rocks close to a fast-flowing stream.
The toad was rediscovered among a group of torrent toads (Adenomus dasi), which it strongly resembles, perhaps why several previous extensive searches of the region failed to identify it.
However, the scientists claim that the Kandyan dwarf toad can easily be recognised by its fully webbed toes and the presence of large warts on its back.
Meanwhile Mendis explains that Adenomus. kandianus is the world’s rarest toad since it was missing for the longest period of time, for nearly 137 years.
“Sri Lanka consists of 111 species of amphibians described so far, and it also carries the distinction of contributing to the highest proportion (60%) to the global list of extinct amphibians according to Kelum Manamendra-Arachchi and Rohan Pethiyagoda in 1998 and 2005,” Mendis revealed.
The Peak Wilderness was designated a sanctuary on 25 October 1940 (Gazette Notification No. 8,675), having an area of about 55,300 acres (22,379 hectares).
According to the current management plan, the geographical area of the sanctuary is about 24,000 hectares, of which 21,175 hectares comprises of natural or semi-natural vegetation.
The remaining area includes tea estates and village settlements while the sanctuary’s eastern boundary is contiguous with the Horton Plains National Park. The Peak Wilderness is also listed as Sri Lanka’s fourth highest peak.
The Sanctuary is one of the few remaining areas in Sri Lanka with a continuous natural forest cover of altitudinal graded forest types, ranging from lowland mixed Dipterocarp forests to montane cloud forests and has its own forest vegetation.
“The sanctuary is rich in bio diversity and covers a large altitudinal range and different climate conditions which is well reflected by its forest type and biodiversity,’ Mendis said.
He went to explain that forests ranging from Tropical Lowland Forests to Tropical Montane Forests can be identified within the area.
“A systematic survey was carried out in order to document the amphibian diversity across an elevation gradient, in the Sri Pada, Peak Wilderness (part of the Central Hills World Heritage Site) of the Central province, of Sri Lanka, in collaboration with the Ministry of Environment and part funded by the Nagao Natural Environment Foundation ” Mendis said.
According to the HFS President his team focused their research mainly in terrains, where not much light has been shed on the diversity by scientists, because of the difficulty to reach these sights due to harsh weather conditions and tough trails.
The field survey was carried out over a two year period and during this time the specimen of the toad was found. “A single specimen each from all three congeners were collected, and are deposited in the Department of Wildlife Conservation (DWC), Girithale National Wildlife Research and Training Center,” Mendis said.
Specimens resembling Adenomus kandianus were recorded from the Peak Wilderness Sanctuary on the 23rd October 2009, as a result of a survey carried out in the region to document the amphibian diversity.
During a nocturnal sampling session, about four specimens of an unusual species were observed, which were sympatric with Adenomus dasi on rocks close to fast flowing streams.
A single specimen was collected in order to taxonomically clarify its identity. Adenomus. kandianus was identified by smooth finger edges, slender habitus and lack of a supraorbital ridge characteristic of the genus Adenomus (Manamendra-Arachchi and Pethiyagoda, 1998) fully webbed toes diagnostic of Adenomus. kandianus (Günther, 1872) and in addition, a uniform golden yellow venter which is absent in Adenomus. dasi and Adenomus. kelaarti).
“Adenomus. kandianus can be confused with Adenomus dasi, because of the similar body size, morphological characters and geographical distributions. But the former can be easily distinguished by the presence of complete webbing on toes in comparison to half webbed toes and the comparatively large warts on dorsum in comparison to the small warts,” Mendis explained.
“Adenomus. kandianus, can also be easily distinguished from Adenomus. kelaarti by the absence of a cranial ridge which is present in Adenomus kelaarti, the presence of cutaneous fold along the edge of tarsus in comparison to the undulating less prominent cutaneous fold, long and very narrow parotoid gland in comparison to the short and narrow gland and the chest and belly rough granular in comparison to the smooth granular among others,” Mendis said.
However the Kandyan dwarf toad’s characteristic of full webbing can only be observed on close examination when the toes are stretched out, and is not visible when live specimens are hand held.
According to Mendis the species was recorded on rocks of river banks close to fast flowing streams at a very high altitude above 1800 meters. All specimens were observed within an area of 200 meters during nocturnal sampling sessions, while the canopy cover was that of a montane cloud forest.
He went on to say that the species was recorded close to fast flowing streams, at relatively high altitudes, suggesting their preference to an aquatic life, adding that their presence of complete webbing on the toes, most probably facilitates their ease of swimming in fast flowing streams unlike the other species of the same genus.
“After the initial sampling session, close to 100 individuals were recorded in an area of 200 m2. However the Peak Wilderness although a part of the recently declared Central Hills World Heritage Sites, is polluted every year from a large number of pilgrims because of its religious importance, especially the streams, and is now under severe anthropogenic pressures,” Mendis said.
The highest point of this mountain range, Adam’s Peak, is a place of worship by all religions in the country and a place of aesthetic beauty, hence millions visit this site every year during the pilgrimage season which lasts for a period of six months.
“This is a time when a large amount of garbage collects, and the natural forest gets over exploited. The survival of this small population of aquatic species re-discovered from a single locality depends on the water quality, and their breeding habitats as they are hyper endemic and are highly vulnerable to environmental changes such as forest die-back which has spread during the past decade possibly due to pollution or climate change which has resulted in a decrease of natural forest cover,” Mendis stated.
He explained that given the high degree of micro endemism and species diversity in Sri Lanka, it cannot be fully excluded that the toad population on which was reported might represent a new, undescribed species rather than Adenomus kandianus.
“However, since no molecular data is available on the types of Adenomus kandianus, its type locality is doubtful, and the encountered specimens agree most closely with the Adenomus kandianus types in morphology, description in 1872. Courtesy: Ceylon Today