Conservationists are hopeful that wildlife coped better with the NSW Blue Mountains fires than first feared after a koala was spotted in the upper reaches of the mountains for the first time in 70 years.

The koala was seen crossing the Great Western Highway near Wentworth Falls, which is 900m above sea level.

The sighting is the first of its kind in the upper Blue Mountains since the 1940s. It is thought that the koala, and others, managed to escape October’s fierce bushfires, which burned through about 140,000 hectares, by fleeing to areas they usually don't inhabit.

“The soil up there is pretty poor so it’s very unusual to see a koala at altitude,” said Dr Kellie Leigh of the University of Sydney, who is mapping koalas in the Blue Mountains.

“People told us not to bother looking up there but we’ve had eight or nine sightings of koalas in unusual areas, probably due to the fire forcing them away from the valleys.”

Leigh said the fires had pushed koalas to the edges of urban areas, including three that emerged from the bush to sit in buckets of water near a blaze that threatened the town of Springwood.

The appearance of koalas has raised hopes that the marsupial was not wiped out in the Blue Mountains by the fires, contrary to initial fears.

“The general thinking was that they just didn’t exist in this area, but we are getting reports that a lot of koalas are out there,” Leigh said. “In some places there wasn’t massively intense burning and the canopy has still got green patches. It really could have been a lot worse and we’re hoping there is some wildlife in there.”

Leigh, through her venture Science for Wildlife, is counting koalas using tracking dogs and thermal imaging drones. She estimates there could be several hundred koalas in the Blue Mountains national park, fragmented into two or three populations. She believes other wildlife may also have avoided the worst of the flames.

“I think we lost a lot of animals, but I think they are making a better recovery than we first thought,” she said.

“Reptiles and possums suffer from fires but we’re already seeing green shoots coming out of gum trees. Things can bounce back quickly and reptiles can move back into a burned area quickly, within a month or so. Fire is a natural part of the landscape, after all. Plants need it to regenerate every few years.”

Justin McKee, a spokesman for the wildlife rescue service Wires, told Guardian Australia the fires had been challenging but that some rescued animals were being released back into the wild.

“A lot of animals came in and not all of them survived, unfortunately,” he said. “We’re still getting a few animals come in because kangaroos, for example, can take a while to lose their mobility from a fire.

“Some animals have been released but others, such as green tree snakes and diamond pythons, will require longer care because they have no habitat to go back to at the moment. That said, we are beginning to see the signs of good growback now.

“We’re excited that animals have survived and we will put them back when appropriate. We’re keeping our fingers crossed that there will be some good species recovery.”