The ACT government plans to begin field trials of a kangaroo fertility drug by July, to determine whether it can deliver the vaccine effectively by dart.
Environment Minister Simon Corbell said the trials would target about 200 eastern grey kangaroos across 10 sites with high female populations.
Carried out by the CSIRO, the Invasive Animals Co-operative Research Centre and the government, the trial - to cost $530,000 over two years - would be the first in the country to determine whether GonaCon could be delivered via dart. Mr Corbell said the drug was known to be effective when administered by injection, rendering kangaroos infertile for up to six years.
"Everyone understands GonaCon works when you inject it by hand, but the problem with that is you've got to subdue the kangaroo first," he said.
"No one else has demonstrated the capacity to deliver GonaCon by dart. We're going to trial whether or not on a scientific basis it's a viable method for controlling captive kangaroo populations and it will inform whether or not we can use it ...
"If successful, dart delivery would provide a cheaper and more efficient way of administering the vaccine, compared to hand injection, making it a more practical option for treating free-ranging kangaroo populations."
Research and planning had begun already, with field trials to begin within about three months. They would be done in small, contained areas so populations could be studied.
The announcement follows considerable controversy each year over the annual cull, between about May and July, in which more than 1000 kangaroos are shot on the city's nature reserves.
Last year, 1519 kangaroos and 514 pouch young were shot over six weeks.
Mr Corbell did not have costs for the fertility trial on Monday night, but said the money was being redirected from internal territories and environment budgets.
Mr Corbell's announcement comes almost a year after Territories Minister Shane Rattenbury announced a trial, which was to be in the Gungaderra Nature Reserve in Gungahlin and involve up to 500 kangaroos.
This week, he said he would have preferred a bigger-scale trial, but welcomed the progress.
"It's about making sure the science is rigorous and the animal ethics are well dealt with and if we can get this trial right that will lead to further increases in scale," he said.
Last year, Mr Rattenbury was working on the fertility trial with animal charity Alphadog Army, run by Marcus Fillinger, who this week announced his candidacy as an independent candidate for the 2016 ACT election.
But Mr Fillinger has heard nothing since about May last year, when Mr Corbell said the government would go to tender, an idea now abandoned.
Mr Fillinger, a tranquilliser firearms expert, now plans to raise money for his own trial, mistrusting the government's motives and frustrated at lack of progress.
Mr Rattenbury said kangaroo population counts were still being done to determine whether a cull was necessary this year.
But Canberrans understood the need for to cull.
"No-one in government likes doing this, but as responsible land managers I think the community understands that we have a job to do here to get the ecological balance right," he said. "I think it is interesting that people who claim to be animal welfare activists are prepared to go and support just one species at the expense of other species such as birds and lizards, when in fact the whole ecosystem is under threat."
Mr Fillinger will stand for election in Mr Rattenbury's seat of Molonglo, and his candidacy will be a direct challenge to Mr Rattenbury's Green support base.
But Mr Rattenbury said he stood proudly on his record on animal welfare, including outlawing battery hen cages and sow stalls with legislation on the table now to outlaw puppy farms.
"The more the merrier" in what would be hotly contested election next year, given the increase from 17 to 25 politicians being elected, he said.
But "Mr Fillinger will of course need to get himself on to the ACT electoral roll to be eligible as a candidate", he said.
Mr Fillinger was unfazed by the comment, saying he believes he is already on the roll, having stood in the 2013 ACT Senate race for the Animal Justice Party. He has a home in Canberra but lives over the border in NSW where he runs his animal rescue charity on a property.