While at the school, he rescued a
rat snake, which led him to move further in field of science. Then he started to rear few non-poisonous snakes, a baby
saltwater crocodile, and a few
sea turtles in his home, and villagers started calling him Hoony Mahaththaya (Mr Gecko) due to his frequent outings around the village to catch
geckos as a food for snakes. At the age of 17, he read the book
Snakes of Ceylon written by
Frank Wall which induced him to start researching snakes throughout the country. In 1964, he joined
Faculty of Medicine, Peradeniya, as the museum technician of the Department of Public Health. He retired from Department of Community Medicine in 2000. He is the founder and president of Amphibia and Reptile Research Organisation of Sri Lanka (ARROS), which he started in 1990. ARROS is the first
NGO in Sri Lanka aimed at reptile conservation. Due to his enormous contribution, de Silva was appointed as the chairman for Declining Amphibian Populations Task Force in the
World Conservation Union (now the IUCN) for Sri Lanka. In 2015, he worked as the co-chairman of the Amphibian Specialist Group of the World Conservation Union. He has published more than 450 research publications on herpetofauna in Sri Lanka for last fifty years. He was the first author to publish a reptile guide with coloured photographs. To create public awareness of reptiles and amphibians, de Silva published the Sri Lanka's first series of posters illustrated with coloured photographs in 1990 and 2001. De Silva organised a number of events at fourth World Herpetology Congress and World Crocodile Congress. In 1991,
University of Peradeniya conferred a
Master of Science degree for his contributions to the field of zoology. He also worked as a visiting lecturer at the Faculty of Veterinary Medicine and Animal Science, University of Peradeniya and
Rajarata University of Sri Lanka. ==Bibliography ==