Koalas were introduced to Victoria's southwest as the cutest of tourism drawcards, but now they're starving and some are marked for death.
A further controversial cull is planned to reduce koala numbers in Cape Otway region, where an "overabundant" population has stripped gum trees bare of leaves.
Victoria's Department of Environment, Land, Water and Planning (DELWP) has confirmed it will soon conduct a week-long assessment of the colony and any unhealthy koalas will be euthanised.
There was a public outcry in March when it emerged more than 600 koalas were secretly culled in the same area, in 2013 and 2014, due to overpopulation and starvation.
DELWP spokeswoman Mandy Watson says foliage has improved slightly in some areas but the koala population is "still high".
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Proactive management is the best way to protect koala welfare, she says.
Wildlife officers will catch a sample of koalas, check and ear-tag them and implant fertility control in females.
"Any unhealthy koalas, which are deemed too sick to survive release, will be humanely euthanised to prevent further suffering," Ms Watson said in a statement on Tuesday.
Australian Koala Foundation chief executive Deborah Tabart said the problem stemmed from bad decisions by past governments.
Koalas were introduced to the area in the 1980s to promote tourism, she said.
"I never see it as an overpopulation of koalas, I see it as an under-population of trees, and nearly 100 years of mismanagement," Ms Tabart told ABC News 24.
She said the Cape Otway koala population should be granted protection.
