Rescued just before the summer bushfires destroyed the Two Thumbs wildlife sanctuary, the wild koalas are now slowly being re-introduced to their old habitat.

Their resilience amid the blackened landscape has surprised the ANU researchers who originally took them in and nursed them back to full health.

"It's very encouraging to see; while the trees are coming back really slowly after the fires, the koalas are appearing to cope with that," ANU co-researcher Dr Karen Ford said.

She said the eucalypts which the koalas need for food are now producing epicormic growth - buds that lie dormant under the bark of a tree and emerge after fire - as part of their recovery.

What was unknown was whether this re-growth, together with any other nutrition that could be found among unburnt trees, would be sufficient for the koalas to survive.

But it appears that the plucky little herbivores, with GPS trackers attached and mini-aerials on their collars, are managing very nicely indeed.

Mining magnate Twiggy Forrest and his wife Nicola's Minderoo Foundation waded in with a $257,000 grant and the Two Thumbs Wildlife Trust with a further $100,000 donation to assist ANU researchers examine how koalas recover after fire and how fire impacts their habitat.

Minderoo's program aims to build an evidence base for interventions to ensure the future survival of wildlife in post-bushfire landscapes, given that the awful intensity of the 2019-20 fires could be repeated elsewhere in the summers ahead.

Two wild koalas were returned in June, and another three in July. More are awaiting their gradual release from custom-built enclosures at Jerangle.

Among those waiting for release are Ian, Paul and Rick, named after the three US airmen who lost their lives in January when their C130 aerial tanker crashed while fighting the bushfires,

"We tagged the trees from where they [the koalas] were rescued so if possible, they are returned to the exact trees where they came from in the first place," Dr Ford said.

"Those out there now have managed to find themselves little patches of trees with canopy intact and they have been using patches of burnt areas as well and are finding no trouble at all in moving around, which is what we really wanted to see."