On Thursday, the ACT government will move to establish the southern brush-tailed rock wallaby as the territory's newest emblem, despite calls for the spot to be shared with popular runner-up the eastern bettong, which lost the public vote by a whisker.

"There can only be one winner," a government spokeswoman said.

The ACT will also begin exploring the creation of an official coat of arms for the territory, she revealed, signalling a likely change to Canberra's flag as well.

When the ABC discovered the ACT was the only state or territory without a mammal emblem last year, it triggered a government inquiry and public poll to choose the right animal for Canberra.

A fierce Twitter campaign soon broke out between finalists Rhonda the rock wallaby and Brian the bettong - a long-time ambassador for Mulligans Flat Nature Reserve.

Eastern bettongs, once extinct on the mainland, are a recent conservation success story for the ACT, where they were reintroduced in 2012.

Brian, who gained fame after being thrown out of his mother's pouch three years ago, emerged as an early favourite.

But, after the shock result saw Rhonda snatch the win by 40 votes, Mulligans Flat manager Will Batson said the bettong had been holding out hope for a dual emblem nod.

Brian was disappointed at the decision, which will be voted on in the assembly on Thursday, but was pleased the campaign had put local wildlife conservation in the spotlight, Mr Batson said.

Rangers at Tidbinbilla said Rhonda, the underdog, deserved the win.

Southern rock wallabies are among Australia's most critically endangered species - only about 40 remain in the wild. A new genetic recovery program is underway in the ACT to rescue the rare southern lineage of the species after historical threats such as deforestation and the fur trade saw their numbers collapse.

Journalist David Sharaz, who was recruited early on by Rhonda to lead her campaign, said it was always going to be tough being the only female in the emblem race, but the plucky little wallaby had prevailed.

"I've spoken to Rhonda and I'm thrilled ... [she] did offer Brian a role in her office but we're yet to hear back," Mr Sharaz said.

The former MIX 106.3 host shrugged off rumours he was the real mastermind (or Steve Bannon-like figure) behind Rhonda's social media campaign, and stressed the wallaby would be retaining full control of her Twitter account when she was installed as the mammal emblem.

"Rhonda feels her role is independent and at arms-length from government interference," he said.

On Wednesday, the government dismissed suggestions that a last-ditch push to tank the vote by a breakaway bettong faction was brewing in the Assembly halls.

But the process had thrown up another glaring deficiency in the ACT, the spokeswoman said. The territory does not have its own coat of arms.

While there is an existing coat of arms for the city of Canberra, she said it included historical design elements no longer relevant to the people of Canberra.

A potential change would consider how to draw attention to the conservation of the ACT's emblems - the existing floral emblem the Bluebell, the faunal emblem the Gang-gang Cockatoo, and now the incoming mammal emblem the rock wallaby, she said.

The government later stressed Rhonda the wallaby was a character created for social media and was not the official mammal emblem, though they did wish her well.