Rodents haven’t had a great rap lately. During last year’s lockdowns, the suburbs of Sydney were invaded by a plague of cannibalistic rats. Not to mention the literal mouse plague more recently terrorising parts of rural New South Wales. But we’re here to say not all rats (and mice). Turn your attention to the positively cute as heck native bush rat. In the battle of ‘native wildlife vs introduced invaders’, this indigenous species is winning at North Head Sanctuary in Manly, where bush rats are successfully reclaiming their territory from gangs of invasive black rats.
Results from recent wildlife surveys found that the population of black rats at North Head has decreased significantly since bush rats were reintroduced to the area between 2014 and 2016; 170 were released as part of an initiative to use native wildlife to outcompete a foreign species and act as a biological control. Black rat numbers dropped from an estimated 112 in 2019 to 29 in 2020, and the decline continued in May 2021, when only eight black rats were captured during a survey of 250 hectares at the sanctuary.
Bush rats are territorial, and as they gain strength in numbers they are able to keep out competitors and reclaim their land from seemingly stronger species. At North Head, reintroducing this native species after reducing the number of black rats is blocking reinvasion. Like a gang of tiny, four-pawed local superhero defenders, the bush rats are also helping to protect native flora and fauna species.
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“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,” said Viyanna Leo, a wildlife ecologist with the Australian Wildlife Conservancy. “Bush rats co-exist with other native species and their presence prevents damaging species such as black rats from consuming the eggs of endangered ground-dwelling mammals and birds.”
“It’s very exciting that this initiative to reintroduce native wildlife in order to remove pests has worked and to have a success story that sees bush rats take back their territory from an invasive species.”
Wildlife surveys at North Head Wildlife Sanctuary in May 2021 also revealed that populations of small mammals remain strong, despite a hazard reduction burn that broke containment lines and destroyed 57 hectares of the headland in October 2020. Ecologists believe fires may have displaced individual animals from their usual habitat leading them to seek shelter near the survey area. Twelve eastern pygmy possums were also recorded including five females with babies in their pouches, indicating that they are breeding and doing well post-fires.
The Australian Wildlife Conservancy delivers conservation science projects including survey work such as this at North Head Sanctuary, which is managed by the Sydney Harbour Federation Trust. Find out more here.