BBC News, Sydney
Animal rights activists in Australia say they will try to prevent the planned killing of more than 400 kangaroos.
The Kangaroo is one of Australia's national emblems
Contractors are preparing to cull the animals on a former naval site in Canberra, after the new government rejected a proposal to relocate them.
The plan is to shoot some 400 kangaroos with tranquiliser darts and then to administer lethal injections.
The government says the animals are overgrazing the grassland.
But animal welfare groups have proposed their relocation, complaining that they have no chance to escape the cull because the land is fenced in.
They have accused the new Labour government of hypocrisy, for trying to protect whales in the Southern Ocean against Japanese hunters, but failing to save kangaroos in their own capital.
Millions of the animals are culled each year, but protesters say this is a special case and have vowed to mount a blockade of the former naval base.
The kangaroo is one of Australia's national emblems - the animal graces the coat of arms that adorns Parliament House.