Native Wildlife Defend Their Territory From Invasive Species Documented in New Study

A conservation survey follows a battle between native wildlife against invasive species at the North Head Sanctuary in Sydney, Australia - and the native wildlife is winning.

The Australian Wildlife Conservancy have reported that native Bush Rats are on the way to reclaim their territory from scattered "gangs" of Black Rats, invasive species that were introduced in Sydney. Recent wildlife surveys revealed that the population of Black Rats at North Head Sanctuary has drastically dropped - from about 112 in 2019 to only 29 in 2020. This downward pattern continued up until recently, in May 2021, when the conservationists only found eight of the Black Rats after surveying 250 hectares of land at the sanctuary.

The Australian Bush Rats: Native Wildlife on Defense

The Australian Bush Rats (Rattus fuscipes) are small, nocturnal animals. They are omnivorous and more importantly, territorial. Capitalizing on their advantage in numbers, they were able to inch forward and reclaim their territory from the invasive species, Black Rats. At the North Head Sanctuary, conservationists reintroduced the native species after reducing the population of Black Rats, which naturally blocks reinvasion from the introduced invasive species.

This work, delivered by the Australian Wildlife Conservancy and is managed by the Sydney Harbour Federation Trust, is among the latest survey work occurring at the North Head Sanctuary. The effort has seen a significant decrease in Black Rats in the area, directly linked to the reintroduction of 170 Bush Rats between 2014 and 2016. It was a unique initiative, using native wildlife to outcompete and drive out foreign invasive species, acting as a natural biological agent.

"Bush Rats and Black Rats may fall under the same category of rodents, but they impact the environment differently. Bush Rats are native and support the local ecosystem by pollinating local trees and flowers right to the tip of each plant," explains Viyanna Leo, a wildlife ecologist with the Australian Wildlife Conservancy. She additionally explains that Bush Rats can co-exist with the other native species and that they also help invasive species like Black Rats from eating eggs belonging to other birds and mammals.

She adds that it was "very exciting" to see this initiative reintroduce native wildlife and see them remove invasive species - pests - in a particular ecosystem.

A Recovering Ecosystem, Thanks to a Natural Biological Agent

"It is very pleasing to see the native wildlife numbers continue to grow as these threatened species further establish their presence at North Head thanks to the Australian Wildlife Conservancy who have worked with the Harbour Trust to re-introduce these species to the site," says Daniel Sealer, Director of Planning at the Harbour Trust. He added that protecting the threatened flora and fauna at the North Head Sanctuary remains a priority of the Harbour Trust.

Also, wildlife surveys at the North Head Sanctuary last May 2021 showed that populations of small mammals in the area are still thriving, despite the hazard reduction burn that previously tore down containment lines and severely damaged 57 hectares of the land last October 2020.