The new plan includes the continuation of culling alongside the ongoing trial and eventual use of a contraceptive vaccine.

The government has spent $600,000 on the fertility trial, which has had shown encouraging results so far according to senior ecologist in charge of the project Claire Wimpenny.

"When you're able to catch the animal and hand inject it with the vaccine it works really well," Ms Wimpenny said.

Capturing Canberra's roos is a time consuming and costly activity with researchers looking for a quicker and cheaper way to administer the treatment using darts.

"We've done some early trials on targets, just testing lots of different dart types because we obviously want to choose a dart that is suitable and humane for using on kangaroos," Ms Wimpenny said.

"We're also looking at a way of marking the animals when they are dart vaccinated so that you can tell in a particular treatment period which ones have been treated or not."

Despite most kangaroos not being able to breed after receiving GonaCon, 13 per cent of roos in the trial have still managed to reproduce.

Ms Wimpenny puts this down to the animals having well developed pouch young when they were administered the treatment, which rendered the drug less effective.

"It"s like any vaccine that humans get, it takes a little while for the immune system to build up a response," she said.

Ecologists have stressed that reduction of Canberra's kangaroo population is essential if other species of native flora and fauna such as the earless grassland dragon and the striped legless lizard are to thrive.

"Kangaroos are an ecosystem engineer, they can change the understory structure through consumption of grass," grassland ecologist Brett Howland said.

"Dingo and man no longer hunt them and so as kangaroo populations increase it's important that we get in and start actively managing these systems," Mr Howland said.

The conservator for flora and fauna Annie Lane said kangaroos still have a place in the local ecosystem, emphasising that the new plan isn't designed to completely eliminate the kangaroo population.

"Kangaroos are an important part of our natural environment," Dr Lane said.

"But research shows that they detrimentally impact those species that rely on the groundcover for survival, food and shelter."

Dr Lane said the team was expecting results from the trial by October.

"We'll have a good idea of whether that method works and then we'll just continue to find out what are the next questions are," she said.