Goodnight, Sam.

One of the few lighter moments after the Black Saturday bushfires was this footage of a CFA firefighter giving water to a koala that had managed to survive hell on earth. Papers and TV news were chock-a-block with stories about 'Sam' and her apparent recovery.

Sadly, Sam was put down today.

One of the brutally hard truths I've learned from volunteering with Wildlife Victoria is that animals like kangaroos and koalas that have adapted to the harsh Australian landscape are capable of masking pain that would turn humans into wailing sirens. What you see on the outside has no relation to their actual health. It even catches experts off-guard:

Southern Ash Wildlife Shelter spokesman Nic Pullen said yesterday the turn of events was extremely distressing.

"Sam was making good progress with her recovery, her burns had healed and she had even developed a strong maternal instinct taking care of some of the orphaned joeys admitted to the shelter over the past several months," Mr Pullen said today.

"The discovery of cysts due to chlamydia is very upsetting for everyone involved in Sam's recovery."

Up to 50 per cent of the koala population is affected by the disease, with past vaccines proving unsuccessful.