A volunteer wildlife carer brought the tiny fruit bat into Ms Allen's practice, Parkway Veterinary Centre in Kambah, desperate for antibiotics. Having already had her rabies shot she became Kevin's full-time carer and nursed him back to good health.

“Oh my god, I loved that bat," she said.

“Walking away from that little bat, when I had to put him in with all of the adults, and he was upside down staring at me - " she said, imitating her beloved fruit bat's sad eyes and then her own sobbing as she waved goodbye.

An article published by the CSIRO's Wildlife Research has valued the work of Australia's wildlife carers at a whopping $6 billion a year.

Report authors Bruce Englefield, Melissa Starling and Paul McGreevy, from the University of Sydney, estimated at least 50,000 orphaned mammals were rescued, rehabilitated and released by volunteer wildlife carers each year,

One joey cost a carer about $2000 a year plus 1000 hours of their life, they said.

The report added that rearing or rehabilitating an injured animal "may have a deleterious effect on the health of wildlife carers, especially those who are suffering sleep deprivation from adhering to a one to three-hourly feeding schedule day and night".

And "wildlife carers do not even have the comfort of knowing their efforts are serving any useful purpose, other than the personal satisfaction of caring", the authors said.

ACT Wildlife wombat and macropod coordinator Lindy Butcher has cared for native animals for more than 20 years. She said most volunteers were involved because they cared about the impact of urban spread on Canberra's native animals.

"Most of our animals come in here as the result of vehicle strikes, cat and dog attacks, caught in netting in fruit trees, so it’s all human impact that brings them into our care, and they all come in traumatised or injured," she said.

"We all do it for the same reason: that we think it’s important to try to recover some of that and get the animals back out into the environment and reduce the losses."

It's not often glamorous work. Ms Butcher's backyard is filled with buried dead animals. She once cared for a silvereye bird for six weeks; on its release from her home's deck it was swooped and killed by a currawong.

Volunteer Cheryl Lefevre has 13 possums and two wombats living in what was once her lounge and dining room. Last week, ACT Wildlife phone and transport coordinator Tabitha Plovits was called out to help a possum bound by a rabbit trap and stuck in a tree, which was eventually euthanased after a traumatic rescue.

But each said it was the wins - the extreme highes among the lows - that kept them going.

“Well, I’m still around after all these years," volunteer Erika Guenther, who first started caring for injured native animals in 1995, said.

"Sure, it affects you sometimes when you have a few dying on you or have to be put down, but there are the good days. And I think there are more good days than bad."

The Wildlife Research article estimated wildlife carers throughout Australia contributed 186 million hours and $370 million to the care of injured native animals.

Applying a $31-hourly rate to the work of wildlife carers, and adding the financial outlay, "the total amounts to about $6 billion of volunteer in-kind and financial input," the report said.

"The wildlife carers who manage Australia's injured and orphaned native animals are a national asset that requires strategic nurturing with empathy, understanding, financial and psychological support if it is to remain viable and sustainable," it said.

Dr Allen, who moved to Canberra from the United States, said she was often bewildered by the community's treatment of native animals.

She encouraged more people to get involved in caring.

"This is the capital of a country and it’s teeming with wildlife," she said.

"It’s special, and you would think if we could make people aware how special it is or that it exists here, that maybe there would be more finances, more people would be interested in helping."

ACT Wildlife is desperate for volunteers and donations. Visit actwildlife.net for more information.