From 1981-82 Pethiyagoda served as an engineer in the Division of Biomedical Engineering of the Ministry of Health, Sri Lanka, and from 1982-87 as director of that institution. In 1984 he was concurrently appointed chairman of Sri Lanka’s Water Resources Board. He served as Advisor on Environment and Natural resources to the Government of Sri Lanka from 2002–2004 and was in 2005 elected Deputy Chair of the IUCN Species Survival Commission. In 2008 Pethiyagoda was elected to the board of trustees of the International Trust for Zoological Nomenclature, having previously served a four-year term as Deputy Chair of the Assurance Group of the British American Tobacco Biodiversity Partnership. In 2009 he was appointed a Research Associate of the Australian Museum, Sydney, and from 2015 to 2018 he served as Chairman of the Sri Lanka Tea Board.
Naturalist life
He resigned from government office in 1987 to commence work on a project to explore the island’s freshwater fishes, which led to his first book, Freshwater fishes of Sri Lanka, a richly-illustrated account of the country’s freshwater-fish fauna. Pethiyagoda diverted the profits from this book to an endowment for the , a foundation he established in 1990 to further biodiversity exploration in Sri Lanka, with the business-model of publishing natural-history books and channeling the proceeds into further exploration and research. Between 1991 and 2012 WHT published some 40 books in both English and Sinhala, including widely circulated titles such as A field guide to the birds of Sri Lanka, one of several titles translated into Sinhala and, aided by a grant from the Biodiversity Window of the World Bank / Netherlands Partnership Programme, provided free to 5,000 school libraries. This program served, for the first time in Sri Lanka, to put scientific local-language biodiversity texts in the hands of young people.
Discoveries
Together with colleagues at WHT Pethiyagoda has been responsible for the discovery and/or description of almost 100 new species of vertebrates from Sri Lanka, including fishes, amphibians and lizards, in addition to 43 species of freshwater crabs. This work also led to the finding that some 19 species of Sri Lankan amphibians have become extinct in the past 130 years, the highest national extinction record in the world.
Recognition
In 1998, concerned by the rapid loss of montane forest in Sri Lanka, Pethiyagoda began a project to convert abandoned tea plantations into natural forest, for which he was honoured by the Rolex Awards for Enterprise. In recognition of his contribution to biodiversity conservation Pethiyagoda, a Fellow of the National Academy of Sciences. In addition to some 60 papers in the scientific literature, his most recently published books are on the history of natural-history exploration in Sri Lanka, Sri Lankan primates and Horton Plains National Park. He is a Research Associate of the Australian Museum and serves as editor for Asian Freshwater Fishes of the journal Zootaxa.
Legacy
Several new species have been named in his honour, including the fishes Dawkinsia rohani and Rasboroides rohani; the microhylid frog Uperodon rohani; the dragon lizardCalotes pethiyagodai; the jumping spider Onomastus pethiyagodai and the dragonfly Macromidia donaldi pethiyagodai. In July 2012 Pethiyagoda and colleagues named a genus of South Asian freshwater fishes Dawkinsia in honour of the evolutionary biologist Richard Dawkins, following which Pethiyagoda told AFP that "Richard Dawkins has through his writings helped us understand that the universe is far more beautiful and awe-inspiring than any religion has imagined". Pethiyagoda also named the freshwater cyprinid genus Haludaria after the Begali youth known only as Haludar, who illustrated the fishes depicted in Francis Hamilton's "Fishes of the Ganges", the founder work of Indian ichthyology.
