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Species richness and diversity of amphibians
in conventional and chemical free agricultural
systems in highlands of Sri Lanka
By D. M. N. P. K. Dawundasekara and Anslem de Silva
Sri Lanka has been an agricultural
country from prehistoric times. Recent
microscopy studies on fossil pollen from
Horton Plains National Park indicate that
selected species have been grown there since
7000 BP (Premathilake and Nilsson, 2001).
Traditional techniques utilized by farmers
in Sri Lanka have included using plant
extracts to repel insects, bird and wild
animals from crops however, pesticides
were first introduced to Sri Lanka in 1946 to
control malaria. Since then there has been
a substantial increase in their use. It was
estimated by the United Nations that in 2005
over 1000 brand pesticide products were
registered (FAO, 2005). During 2005-2009
Sri Lanka imported the following metric
tonnages (mt) of a) non-diluted insecticides
761.6 mt; herbicides 1008.7 mt and of b)
diluted insecticides 7083 mt; herbicides
15,110 mt; fungicides 3952.5 mt (Registrar of
Pesticides, 2010).
A considerable number of human deaths
occur in Sri Lanka annually due to the toxic
effects of pesticides. According to the Ministry
of Health (2007) it is the 12th ranking cause
of hospital death in Sri Lanka: often due to
self ingested pesticides as poison while some
poisoning is caused while spraying pesticides
on paddy and vegetable fields. There are, however few reports
of the direct effects of pesticides on amphibians in Sri Lanka (de
Silva, 2009; de Silva & Dawundasekara, 2010). Frogs that were
once common in paddy fields in the past are now less common
(de Silva, 2001). Based on a whole range of previous studies it is
reasonable to assume that the use of pesticides and herbicides
in paddy, vegetable and ornamental flower cultivation could be
a factor responsible for reducing frog populations (de Silva and
Dawundasekara, 2010) in these habitats. High application rates of
nitrogen fertilizer may be another contributory factor. Nearly one
third of Sri Lanka’s land is cropped, and according to the World
Bank in 2008 farmers in Sri Lanka used 284.3 kg of fertilizer
per hectare of arable land which is a higher level of usage than
elsewhere in the region (e.g. India – 153.5 kg.; Bangladesh –
164.5kg.; Indonesia – 189.1kg).
One hundred and ten species of amphibian are known from the
country (de Silva, 2009; Manamendra-Arachchi & Pethiyagoda,
2006; Meegaskumbura & Manamendra-Arachchi. 2011).
The ongoing island-wide survey to investigate the pattern of
malformations, injuries and parasitic infections in the amphibians
30 | FrogLog Vol. 98 | September 2011
Top left. Pseudophilautus alto observed in 5 plots. Top right. Pseudophilautus microtympanum observed in 7
plots. Bottom. Taruga eques observed in 9 plots. Photo: Anslem de Silva and D. M. N. P. K. Dawundasekara.
of Sri Lanka by one of us (AdS) has shown several interesting
cases of malformations of amphibians, including direct toxic
effects of agrochemicals (de Silva, 2009).
The present preliminary study was carried out to see the effects of
the use of agrochemicals on the species diversity and richness of
amphibians in some high altitude vegetable plantations.
Material and Methods
Ten vegetable plots at Blackpoll (app 1600 m above sea level),
Nuwara Eliya district were surveyed using patch and visual
encounter survey methods (de Silva & Mahaulpotha, 2007).
Each vegetable plot was approximately 0.1 hectare in extent.
Amphibians, reptiles and insects present were hand collected for
identification, examination and recording and then released at
the point of collection. Full water chemistry and bacteriological
examination of each agro-well was conducted at the National
Water Board Laboratory, Peradeniya. The data was analyzed using
the SAS System using Two Sample T-test (pooled).