Scientists say there is evidence of dibblers, a species once considered extinct, are breeding on a remote Gascoyne Island.
Last year a number of the marsupials, bred at Perth Zoo, were released on Dirk Hartog Island.
The translocation was part of the Return to 1616 project.
Dirk Hartog Island restoration project research scientist Saul Cowan said in May, while island was being monitored the team was lucky enough to catch a female dibbler.
A dibbler is a small carnivorous marsupial, part of the same family as the quoll and the Tasmanian devil.
"For the dibblers as a species it's quite significant. They're listed as endangered, and they were previously thought to be extinct," Dr Cowan said.
"Establishing a population on Dirk Hartog Island would be really good for ensuring we don't lose the dibbler."
The animal was thought to be extinct for 50 years before a pair was discovered at Cheynes beach near Albany in 1967.
Dibblers used to be widespread throughout coastal areas.
Return to 1616
On October 25, 1616, Dutch explorers landed on the remote island, off the coast of Shark Bay.
Over time feral cats, goats and sheep were introduced onto Dirk Hartog Island.
The introduction of these animals changed the vegetation and reduced the food and shelter for native species.
With these introduced species now removed and eradicated from the island, an ecological restoration project seeks to return the isle to what it was like before Dutch explorers stepped foot on the land.
The dibblers were the fourth species to be translocated onto Dirk Hartog island and Dr Cowan said they were the hardest to monitor.
He said in terms of the project it was exciting that the dibblers were breeding.
"A species that we thought might be quite tricky to establish on the island appears to have settled in well and establishing, breeding and that's really exciting that we might be able to establish a new population there," Dr Cowan said.
More species to be released
Dr Cowan said the evidence Dibblers were breeding would give the team confidence they were on the right track.
The team is working to introduce more species onto Dirk Hartog Island.
"We've got a few other small mammals in the pipeline including the greatest stick-nest rat and shark bay mice," he said.
"In coming years I think there will be seven species including one bird so we've got a little bit more work to do."
