Young eastern grey kangaroo joeys are being bludgeoned to death in increasing numbers during the ACT's annual cull, a draft management plan for the species has revealed.
While the number of kangaroos culled has risen by 30 per cent in the past three years, the number of pouch young - joeys aged up to 9.3 months - killed has increased by 42 per cent.
However a spokesman for Territory and Municipal Services said the increase was in line with an overall rise in the number of kangaroos being culled.
"The number of kangaroos killed in the last three years has increased (from 1521 to 1689 to 1989) so it follows that over the same period more pouch young will also be required to be euthanised," he said.
Kangaroo culling is a divisive issue in the ACT, with animal welfare groups vehemently opposing the practice on the grounds that it is unethical and could damage the territory's tourism industry.
Activists also claim the overabundant status of the animal is false and that the species is in fact in decline.
The ACT cull is deliberately timed to minimise the rate shooters encounter mothers with joeys reliant on their milk, although pouch young at this age are impossible to detect.
After killing the kangaroo, shooters must check its pouch for any young.
If there are young, the joeys are killed through a "single forceful blow to the base of the skull", a practice Territory and Municipal Services said was in accordance with the national code, which is endorsed by the RSPCA.
"Most young are very small, in the very early stages of their development," the spokesman said.
"The ACT is the only state or territory to designate a culling season (March to July) purely as a management response to minimise the number of older joeys required to be destroyed.
"As such the prescribed culling season has been shown to be effective in protecting young kangaroos at an age when they are vulnerable to being orphaned by the shooting of the mother."
The reporting of culled pouch young began in 2014 despite shooting taking place annually from 2009.
About 35 per cent of kangaroos shot in 2014 had pouch young, analysis shows.
The following year about 41 per cent of culled kangaroos had pouch young. That proportion dropped slightly to 40 per cent in 2016.
Since the count began, more than 2000 pouch young have been euthanised.
The ACT government's position on kangaroo culling is that it is necessary to protect biodiversity and to prevent starvation among the kangaroos and species.
"Excessive kangaroo grazing pressure impacts the specialised habitat of threatened species resulting in habitat loss and degradation which may lead to the death of significant parts of a population through starvation or predation," the draft management plan reads.
It's an ethical quandary but one activists say can be stopped by halting the cull and letting nature take its course.
"The way they kill them is horrible but leaving them to die of hypothermia or dehydration or hit by cars is almost even worse. It's just distressing," Frankie Seymour, co-founder of the Animal Protectors Alliance, said.
"The science shows you don't need to cull kangaroos anyway because their population grows to carrying capacity of land and stabilises so it's impossible to find out why they do it. It's unnecessary and unbelievably cruel.
"If you are going to kill them though find a more humane way of doing it than bashing their [joey's] brains out. It's a massacre."
Public comment on the the draft management plan closes on March 24.