A kangaroo exclusion fence at Scottsdale property, run by Bush Heritage. Foreground shows grassland recovery without roos grazing. Credit:Bush Heritage "It's a difficult but necessary approach to try to get the numbers to where we can get the natural eco-system flourishing. We're managing for hundreds of species here, not just one." Vulnerable species include Rosenberg's monitor lizard, the speckled warbler, curved rice flower and the yellow-box grassy woodlands, a critically endangered eco-system nationally. Bush Heritage is bracing itself for a backlash from environmentalists as details of culling plans surface. Animal rights groups have also been seeking documents under freedom of information laws about past kangaroo killing. Mr O'Neill said the group had secured licences from the NSW Office of Environment and Heritage to kill "about 900" kangaroos, using professional shooters.

A kangaroo shot during the annual culling in the ACT. Credit:Carolyn "We've still got too many roos," he said. Frankie Seymour, a campaigner against the annual kangaroo culls in the ACT and a spokeswoman for the Animal Justice Party candidate, said the killings could not be justified. One of the four fenced off areas aimed at keeping the kangaroos at bay at the Scotsdale property. Credit:Bush Heritage "It's just horrifically cruel," Ms Seymour said, noting that, even if codes of practice were followed, joeys "have their brains bashed out", unweaned joeys were left orphans, and social structures were torn apart.

Moreover, it was not clear kangaroos were doing well, with evidence pointing to reductions throughout their range, which stretches from Queensland to Victoria, she said. Numbers debate Assessing the health of the eastern grey population can be difficult, hinging in part on the starting point. George Morrison, an explorer who is best known as a correspondent for The Times in Beijing at the turn of the 20th century, claimed not to have seen a single kangaroo when he trudged 2700 kilometres overland from the Gulf of Carpentaria towards Melbourne in the early 1880s. A CSIRO study in 2014 found eastern grey kangaroo densities in the ACT had "substantially increased" since the 1960s, although links between numbers and plant species "richness" were uncertain.

The ACT's own Kangaroo Management Plan was cited by Bush Heritage to justify its earlier licence to cull submitted in 2016. The plan stated that a carrying capacity of 60-150 eastern greys per square kilometre would "conserve the natural integrity of native grasslands and result in the maintenance of habitat for all plant and animal species". As of the autumn of 2016, the kangaroo capacity on Scottsdale was estimated at 324 roos per square kilometre, Bush Heritage said, and numbers have remained high. 'Done well' An OEH spokesman said eastern grey numbers fluctuated with conditions.

Surveys suggest the numbers in NSW "are down on 2016 from 6.3 million to 3.8 million" last year. Last year, the state issued non-commerical permits for 2111 eastern greys, down on 2015, the spokesman said. Mark Eldridge, a principal research scientist at the Australian Museum, said eastern greys were "certainly one of the most widespread and abundant macropods in NSW". Increased access to water from dams, more cleared land for grazing, and the removal of predators such as dingoes had all helped to boost roo numbers. "Thev've certainly expanded their range westwards through the provision of water points," Dr Eldridge said. "They are one of the few species that have done well out our modification of the landscapes."

'Vexed issue' Catherine Herbert from Sydney University is researching fertility controls for kangaroos using darts to dispense contraceptives remotely. So far, though, the drugs are only effective for 18 to 24 months. The treatment costs of about $50 per animal would probably make the process costly for broad-scale use, she said. "Outside of urban areas, culling is pretty much the only way to secure a population reduction in the short term," Associate Professor Herbert said. Dr Eldridge said fencing out kangaroos was another option but that could be expensive and would also stop movement of other species "which you may not want to do from an ecological point of view".

Similarly, relocation was stressful for roos and potentially dangerous for both animals and humans, even if a suitable home could be found. "In rural Australia, that's a pretty vexed issue" with an unknown success rate, Dr Eldridge said. "Maybe a bullet - bang, you're dead - is better than starving to death in an area where you can't survive."