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LIVESTOCK:
University of Canberra
PEST CONTROL
Laureta
Wallace
FreecalL 1800 677 761
Vigilance vital to
restraining rabbit numbers
kondinin group
At a glance
Rabbit haemorrhagic disease
(RHD), originally named
calicivirus, has been successful
in cutting Australia’s rabbit
population but there is some
evidence that its impact is waning.
Australian Wool Innovation-funded
research has revealed evidence
that rabbit numbers are
slowly increasing in southeastern Australia.
A new tool is set to give farmers
the ability to assess their rabbit
population and the damage they
are doing to biodiversity, enabling
them to decide whether to carry
out control measures.
Continuing research into rabbits
in Australia will look at whether
genetic resistance to RHD is
emerging in the rabbit population;
the economic impact of rabbits
at their current population level
and the impact of rabbits on plant
diversity.
Biological control has given Australian farmers the upperhand when it comes
to rabbit control. But their most useful weapon, the rabbit haemorrhagic
disease (RHD) or calicivirus, might be losing its punch and farmers are urged
to be vigilant when it comes to managing rabbit numbers.
Two rabbits per hectare halve the growth
potential of native trees and shrub seedlings
and at 10/ha they allow weeds to replace
perennial native grasses, an Australian Wool
Innovation-funded study has revealed.
The study, also funded by Meat and
Livestock Australia, has found rabbit
numbers in south-eastern Australia are on
the increase despite the population having
been kept low for some years by the rabbit
haemorrhagic disease (RHD).
The research programme headed by
the University of Canberra’s Brian Cooke
has developed a tool for land managers
that will enable them to assess their rabbit
population and the damage they are causing
to the property.
The evidence
A survey of remnant vegetation at 220
sites adjacent to farmlands in south-eastern
Australia showed that rabbits were present
in 54 per cent of sites and were causing
noticeable vegetation damage to 26 per cent of
these sites.
Dr Cooke said rabbits did little damage
to crops at low levels but at just one or
two per hectare were capable of removing
70 Farming Ahead June 2008 No. 197 www.farmingahead.com.au
all seedlings of the more palatable native
trees and shrubs and exacerbating weed
competition with native flora.
He said most producers were not aware
of their rabbit problem until acute rabbit
damage was observed.
Rabbit numbers in
south-eastern Australia are
on the increase despite
the population having been
kept low for some
years by the rabbit
haemorrhagic disease.
The tool kit
The assessment tool, developed by
Dr Cooke, allows land managers to score
their rabbit abundance and vegetation
damage and quickly decide on actions
necessary for reducing rabbits and
maintaining biodiversity.
Applicable to native vegetation on
roadsides, reserves and natural shrub-lands
LIVESTOCK:
PEST CONTROL
used for pasture, the tool has been tested by
Landcare groups, farmers and government
agency staff and has been progressively
improved where needed.
Dr Cooke said few producers regularly
assessed their rabbit problem or treated
their control like that of weeds.
He said the assessment tool had given a
solution to at least one part of the problem,
by developing a simple method to quickly
assess a situation and decide whether rabbit
management is needed. The assessment
tool is nearing finalisation and will be
available soon.
Other research
Data from Australian studies in
temperate, Mediterranean and arid climatic
zones was thoroughly reviewed to bring
all the information into a form where it
was readily compared between sites and to
assess regional variations and patterns in
the behaviour of the disease.
With evidence that RHD is
starting to wane, AWI and
MLA are also continuing their
research into new rabbit
control methods.
R
Is RHD doing its job?
Rabbit haemorrhagic disease (RHD),
originally called Calicivirus, was
shown a short time later that rabbits were
also developing natural genetic resistance
to the disease.
introduced into Australia a decade ago
and significantly reduced rabbits in
many areas.
The most gains were achieved in the arid
zone where control always had been costly
relative to the productivity of the land.
The economic benefits of effective
control have been estimated at
$300 million annually across Australia.
Rising numbers
But recent spotlight counts of rabbits
in north-western Victoria and the Flinders
Ranges in South Australia suggest a
disturbing trend.
Rabbits might be starting to
increase again.
Control measures
An increase in rabbit numbers is not
entirely unexpected because Australia had
a similar experience with myxomatosis.
When myxomatosis was introduced into
Australia in 1950 it killed more than 99 per
cent of the rabbits that became infected.
The economic benefits were enormous
but it took only a few years before weaker
strains of the virus were found and it was
Resistance accumulated over the next
10–15 years to the point that, by the
mid-1960s, rabbits were again becoming a
problem in many areas.
Myxomatosis still continued to kill about
50% of infected rabbits but because
rabbits ‘breed like rabbits’ it was not
enough to keep rabbits below the threshold
where damage to pastures and crops
became significant.
As a result, alternative rabbit control
methods were developed including
improved poisoning methods, development
of warren ripping and new
biological control agents to help
support myxomatosis.
Vigilance is key
Having two lethal viruses acting on
rabbits is better than one but there is no
room for complacency.
Given the rate of development of
resistance to myxomatosis, it would be
unwise to simply ‘sit back and see what
happens’ with RHD. An active approach is
essential.
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Farming Ahead June 2008 No. 197 www.farmingahead.com.au
71
LIVESTOCK:
PEST CONTROL
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As a part of the research, Australia’s rabbit
population and management strategies will
be compared with those overseas.
Researchers will ask what is happening in
Europe where RHD spread some five years
earlier than in Australia.
Young rabbits from many different parts
of Australia were also collected to see if they
are developing resistance to RHD.
The other part of the question, about
possible changes in the virus, is already
being tackled by collaborators in the project,
the Animal and Plant Control Group
in the Department of Water, Land and
Conservation, South Australia.
Calculating the costs
The third and fourth parts of the project
are aimed at assessing the economic and
biodiversity costs of rabbits at their present
relatively low levels. By obtaining this
information, it will be possible to determine
what more needs to be done.
If rabbits are shown to be developing
genetic resistance to RHD, the question then
could be what would land managers lose if
rabbits resumed their former numbers?
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Rabbit control: an investment
in land and pocket
Victorian farmer Jonathon Tischler
(pictured above) said reducing rabbit
common. With rabbit numbers cut, dust
storms are of the past.
numbers could improve stocking
capacity dramatically.
He said biological control was essential
to the continued control of rabbits. He said
tasks such as ripping and baiting were just
added tools.
Jonathon is a former manager of
Banongill, a mixed farming enterprise
in Western Victoria. From his experience
cutting rabbit numbers significantly could
see stocking rates increased by up to 20 per
cent because of the increased feed.
B LAC K
He said rabbits not only removed
perennial pastures and spread annual weed
seeds but they also ate new tree shoots.
At ‘Banongill’ rabbits completely sabotaged
an attempt to create a shelter-belt.
Pre-stabilised non brittle sheep
ear tags in 20 different colours
With the rabbits gone, ‘Banongill’ now
boasts a shelter-belt of sugar gums, blue
gums and eucalypts.
2008 Year Colour is
(Code A4)
DEEP INDENT HOT-FOIL STAMPING
IN CONTRASTING COLOUR
Lot 440 Tudhoe St | Wagin | WA 6315
PO Box 89 | Wagin | WA 6315
Ph (08) 9861 1290 Fax (08) 9861 1468
e: [email protected]
72 Farming Ahead June 2008 No. 197 www.farmingahead.com.au
Jonathon is hoping to keep producers
aware of controlling rabbits and is a
member of the Rabbit Management
Advisory Group working with Australian
Wool Innovation and other industry players
on projects to assess the threat posed by
rabbits to Australia’s livestock producers.
He said rabbits had ‘gone off’ the front
page of newspapers but the problem must
remain embedded in the minds of not just
farmers but all land managers.
Jonathon said 60,000 trees had been
planted at ‘Banongill’ since rabbit
haemorrhagic disease was introduced
during April 1996. Perennial pasture
growth is also pushing out weeds.
Now farming 4000 sheep on his own
property, Jonathon sees rabbit control
as a part of his overall environmental
management and believes when it comes
to rabbits, environmental and economical
sustainability go hand in hand.
Jonathan said with rabbits eating the
ground bare and their warrens opening
the higher ground, dust storms were also
He said rabbit management was not
cheap but the benefits far out-weighed
the costs.