The local council said it authorised the 140 eastern grey kangaroos to be shot on the mountain for the first time this year. The cull, carried out under licence from the NSW Parks and Wildlife Service, has at least halved the area's kangaroo population, according to NSW Government estimates.

But environmentalists are equally concerned about the loss of young joeys.

Bathurst Regional Council said the cull was needed to ensure the safety of drivers and visitors when the race started on Thursday. During the 2007 race a kangaroo was filmed hopping on to the track and weaving in between cars before escaping over a crash barrier.

"There were safety concerns not only for the various races but for the 300,000 visitors we get there each year," said the council's general manager, David Sherley. "In previous years we've been able to maintain safety by other methods, but the population has been rising for a while now."

But a Bathurst environmental consultant, Ray Mjadwesch, said the cull, which was completed on Wednesday, could not have been humane.

"It would have been an incredibly terrifying experience for the joeys, being pulled out of the pouch after their mother fell over," he said.

The NSW Greens also believe the kangaroo cull was cruel and unnecessary.

"There are other more humane and ethical ways of managing the possible safety risks," said the NSW Greens MP Lee Rhiannon. "[The] council could herd the kangaroos away before the race to provide safety for them and motorists."

The NSW Department of Environment and Climate Change said the cull had been carried out under licence and the contractors hired for the shoot had followed the guidelines closely.