UNSW Faculty of Science media release Friday 30 October
A plague on their house, but Sydney's bush rats fight back.
Sydney’s native bush rats were unintended victims of a campaign to exterminate foreign black rats
during a plague epidemic in 1900, according to new research by scientists who plan to reintroduce
the native rats into bushland around Sydney’s harbourside suburbs.
A team of Sydney researchers is conducting the three-year experiment to test whether native rats
can mount a counter-offensive against the black rats, which were targeted during the epidemic
because they bore disease-carrying fleas that spread easily to people living in poor housing and
unsanitary conditions around Darling Harbour and The Rocks areas.
The Sydney epidemic of 1900-1905 claimed more than 163 lives and was part of a plague pandemic
affecting dozens of countries between 1850 and 1912.
In a bid to limit panic and the mounting death toll, the NSW Government offered six pence – four
dollars in today’s economy – as bounty for the body of every rat delivered to a purpose- built city
furnace established in Bathurst Street.
The eradication campaign was highly successful: more than 100,000 rats were culled during the first
six months of the program, although the unofficial death toll was probably much higher.
But it also led to the indiscriminate killing of harmless native rodents, according to UNSW biologists
Dr Peter Banks and Dr Grainne Cleary.
“Historical records and photographs suggest that harmless rodents such as water rats and the native
bush rats were caught up in the culling of black rats,” says Dr Banks. “Land-clearing for the suburbs
of Mosman, Cremorne and Manly then isolated bush patches on harbour foreshores, depriving the
native rodents to recolonise bushland habitats. As a consequence, native bush rats have been a
rarity in Sydney ever since – the last confirmed sighting in the city was in 1901.”
Despite the black rat's fearsome reputation, Dr Banks says early experiments at Taronga Zoo showed
that it is "easily bullied" by native bush rats. The team believes that they are likely to “evict” the
invaders from bushland when they are reintroduced, with resulting benefits to many other species
preyed on by black rats – notably native birds whose eggs are taken.
Beginning next year, the campaign aims to trap 70 per cent of the vermin rats in four Mosman and
Cremorne areas before releasing bush rats in these areas from 2011.
If successful, the trial could be expanded to drive the pests out of suburbs across the city.
The Australian Research Council has awarded the team Linkage Grant funding of $365,000 over the
next three years to protect rare and endangered wildlife by using reintroductions of common native
species as a block to reinvasion following pest control.
The initiative is led by UNSW and Sydney University scientists supported by the NSW Department of
Environment and Climate Change, NSW National Parks and Wildlife Service, Taronga Conservation
Society Australia, Mosman Municipal Council, Australian Wildlife Conservancy, Landcare Research
and Rentokil Initial Pty Ltd.
Media contacts:
Dr Peter Banks: 0402 908 909,
UNSW Faculty of Science: Bob Beale 0411 705 435
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