A Helen's Flying Frog perches on a branch in Nui Ong Nature Reserve in Vietnam's Binh Thuan Province, in this May 23, 2009 handout picture provided by the Australian Museum. [Photo/Agencies]

SYDNEY - An Australian biologist and Vietnamese colleagues have made a surprise discovery - a new species of flying frog gliding and jumping around less than 100 km from one of Southeast Asia's busiest cities.

Jodi Rowley and her team were conducting an amphibian survey between two patches of lowland forest in the middle of agricultural land criss-crossed by farmers and water buffalo each day, some 90 km (56 miles) from Ho Chi Minh City, when they made their find.

"And...there on a log just sitting on the side of the path was this huge green flying frog," said Rowley, amphibian biologist at the Australian Museum.

"To discover a previously unknown species of frog, I typically have to climb rugged mountains, scale waterfalls and push my way through dense and prickly rainforest vegetation."

The 10-cm (four-inch) bright green frog with a white belly managed to evade biologists until recently by gliding between treetops 20 meters (yards) up, only coming down to breed in temporary rain pools.

Though discovered in 2009, it has taken until now to identify it for certain as a new species. It has been named Helen's Tree Frog (Rhacophorus helenae) after Rowley's mother.

The discovery highlighted the need for conservation in lowland forests, which have come under huge threat, Rowley said. The two patches of trees that are home to Helen's Tree Frog are surrounded by rice paddies and agricultural land.

"We really don't know what's out there still in this part of the world," Rowley said.

She added that her mother, suffering from ovarian cancer, was very excited about having the "charismatic" amphibian named after her.

"I thought it was about time that I showed her how much I appreciate everything she's done for me," Rowley said.