The federal government has killed nearly 14,000 kangaroos on a military firing range east of Canberra in the past four years, internal Defence Department documents reveal.
The mass cull of adult kangaroos and their joeys, detailed in documents released under freedom of information laws, has been branded a "dirty little secret" by animal rights activists.
Operating under a "licence to kill" issued by the ACT government, the Defence Department has hired shooters to destroy the animals grazing the grasslands of the Majura Training Area, in the east of the ACT.
The scale of the operation dwarfs the territory government's controversial annual cull of eastern greys in the Canberra Nature Park around the capital, which typically kills fewer than 1500 animals each year amid a regular storm of protest, legal challenge and media coverage.
But the culling at Majura has been carried on quietly since it began in 2009, after a bitter legal fight with animal rights activists, with the killing of more than 7000 animals.
In 2010, another licence to kill was approved by the ACT Conservator of Flora and Fauna and 4300 kangaroos were killed at Majura.
There was no cull in 2011 but last year the shooters destroyed 2300 animals and this year, according to a Defence spokesperson, 203 kangaroos were killed.
The last time a cull of kangaroos on Defence land attracted headlines there was international controversy over the killing of 513 animals at the old Naval Signals Transmission Station in Belconnen.
Defence says it has legal obligations to protect the two endangered habitats on the firing range, areas of natural temperate grasslands and yellow box gum grassy woodlands, and the nine endangered species that live there, from overgrazing by the kangaroo population.
"The kangaroo population at Majura Training Area needs to be delicately balanced with the available food supply for the entire ecosystem," the internal documents state. "Keeping a smaller population of kangaroos alleviates the grazing pressure on the grass biomass, ensuring the grasslands are able to support kangaroo and other species into the future."
The training area, used to train cadets from Duntroon Royal Military College and other ADF units, has about 3242 hectares that are considered good kangaroo habitat and Defence says the "recommended carrying capacity" is less than one kangaroo per hectare.
In the May 2012 kangaroo census of the area, carried out before that year's cull, there were 4460 of the animals on the range.
Animal rights activists reacted with anger to the revelation of the culling. Veteran advocate and Animal Justice Party Senate candidate Marcus Fillinger labelled the cull a "slaughter".
Mr Fillinger, who is campaigning for non-lethal ways to control the territory's kangaroo population, vowed that he and his colleagues would step up protests against culling on Defence land.
"Unfortunately as most slaughters conducted on Defence land, this has always been a dirty little secret," the campaigner said.
"Now that it will be widely publicised it will be vigorously pursued by those with non-lethal solutions and held to account.
"It's a disgrace that in an advanced society in the year 2013 ignorant killing sprees are regarded as wildlife management or ecological damage mitigation to threatened species."