Defence contractors are preparing to cull hundreds of kangaroos at a Canberra site in another about-face, after the federal government refused to foot the bill to move them.
After moving in March to kill the kangaroos at the former naval station for environmental reasons, Defence stopped the cull to further study moving the animals interstate in the face of protest actions.
Defence spokesman Brigadier Andrew Nikolic said the department had thoroughly examined the proposal but found it would be to costly.
"The federal government has withdrawn its support for a translocation research project as it does not consider it to be a cost-effective use of taxpayers money," Brig Nikolic said in a statement.
Defence estimated the cost of relocation at $3.5 million.
Eight police officers were on site barricading the entrance, where hundreds of protesters are expected to arrive on Saturday.
Six animal welfare protesters gathered there and said they will stay until the matter is resolved.
Protester Tigga Williams fears the cull will become a "bloodbath".
"The kangaroos are going to be breaking their necks and legs on the fences as they try to escape because you just can't get a kangaroo to go where you want it," Ms Williams told AAP.
"As soon as this begins they will panic and it will turn into a bloodbath."
An ACT park ranger's vehicle was seen entering the site carrying equipment including including hessian bags and a sharps disposal unit.
Hessian-covered fencing has been erected to pen the animals and about five large freezer boxes have been put on the site.
The Defence Department said contractors hired to conduct the cull would be tranquillising the kangaroos and then giving them lethal injections.
Animal Liberation ACT head Bernard Brennan said the protesters were prepared to do anything stop the cull from going ahead.
"We will start up our vigil and keep an eye on the place and we will just have to do whatever it takes to stop the cull."
Wildcare vice president Greg Tarlinton said he was very surprised by Defence's decision.
"We have been trying to assist Defence to put this translocation into place they adopted it but now they have backflipped," he said.
Mr Tarlinton said Defence made the decision because culling the animals was easier than translocating them.
"There is very little difference cost-wise one way or another. This is not about the cost, culling is just the easier option," he told AAP.
"I also think that there is a lot of pressure coming from the ACT government to go ahead with the cull."
An ACT government report released earlier this year recommended the cull to protect lowland native grasslands and threatened species.
Brig Nikolic said the ACT government and Defence agreed that the kangaroo population at the site was overabundant and unsustainable.
He said at last count in December 2007, there were about 590 kangaroos at the site. About 400 will be culled.
"Defence is committed to sustainable environmental management, protecting endangered ecological communities and threatened species and humanely managing over-abundant species," he said.
The planned cull had drawn international condemnation by animal activists including British group Viva!, which has the support of celebrity rock stars Sir Paul McCartney and Chrissie Hynde.
