The critically endangered purple-faced leaf monkey can occasionally be spotted in Colombo's suburbs, while the brown saucer-eyed loris lives in the island's Horton Plains national park.
"The loris is rare. Few sightings have been made," said Nalin Perera of the International Conservation Union in Sri Lanka.
Traditionally the loris has been killed for the supposed medicinal properties of its body parts.
Sri Lanka is also a paradise for butterflies, dragonflies, leopards and exotic birds, who are found in abundance in the island's rainforests and jungles, said Chandra Jayawardene, a naturalist at the Hotel Vil Uyana.
Around 243 species of butterflies and 118 species of dragonflies have been discovered so far, Jayawardene said.
Wijeyeratne said the leisure industry was counting on Sri Lanka's natural wonders to bring foreign visitors to the tropical island, adding that "conventional tourism is in trouble".
Sri Lanka's golden beaches, tea plantations and ancient religious sites