Download Rabbit fact - Hunter Wetlands Centre

HWC FACT SHEET – CONTROL OF RABBITS
AT THE HUNTER WETLANDS CENTRE
Introduction
Hunter Wetlands Centre Australia (HWC) is an internationally recognised Ramsar wetland. In
order to protect our fauna and flora we have a pest control program, which recently saw rabbits
start to enter the property again after many years of absence. With assistance from the
Hunter-Central Rivers Catchment Management Authority (CMA), HWC was able to look at
setting up a monitoring and control program to prevent the establishment of the rabbit pest on
the site. This fact sheet provides an insight into this program and pest problem.
History
The European rabbit (Oryctolagus cuniculus) is native to north-western Africa, Spain and Portugal. The first successful introduction of rabbits to the Australian mainland is thought to have
originated from a shipment of wild rabbits in 1859 to ‘Barwon Park’, near Geelong. The spread
north and west was rapid, by 1886 they had reached the Queensland border.
European rabbit Oryctolagus cuniculus
Impacts
The rabbit is considered to be Australia’s most damaging vertebrate pest and has adverse effects
on pastoral and crop industries, as well as native fauna and flora.
Native fauna suffer from direct competition with rabbits for food and shelter. Grazing, browsing
and ringbarking of native flora have caused declines in native species and facilitated the invasion
of exotic species. Rabbits are commonly believed to cause damage only when they occur in
higher numbers, but in areas of low productivity, densities as low as one rabbit per hectare can
prevent native plant regeneration.
Erosion caused by rabbits in a gully in
South Australia
Distribution
Rabbits now inhabit approximately 4 million sq. km of Australia, mostly south of the tropic of Capricorn. They have become
established in environments ranging from sub-alpine areas to stony deserts, and from sub-tropical grasslands to wet coastal
plains; but particularly in areas with Mediterranean climates.
Habitat
Rabbits prefer short grass areas (naturally semi-arid areas or heavily grazed pastures), with harbour (e.g. warrens, blackberries, fallen logs, native vegetation) nearby. In suitable habitats, most rabbits live above ground and need burrows only for
breeding.
Diet
Rabbits are herbivorous and eat a wide variety of plants, including crops, roots, pastures, young trees and young vines. as calculated from maintenance requirements, approximately nine rabbits are equivalent to one DSE (dry sheep equivalent). Rabbits
can graze plants to ground level and prefer soft, short and succulent plants rather than woody or stalky taller species. Grazing
generally continues throughout the night for 2.5 to 6 hours.
Reproduction
Rabbits can breed at any time, provided there is feed. Both males and females reach sexual maturity between 3 and 4 months
of age. The gestation period for rabbits is 28 to 30 days. Under very favourable conditions an adult female can produce seven
or eight litters in a year, but more commonly three to five.
Mortality
Two of the most devastating diseases to rabbits are myxomatosis and rabbit haemorrhagic disease (RHD), commonly known as rabbit calicivirus disease (RCD). This can commonly cause
70% mortality. These diseases require vectors, close contact, mosquitoes or rabbit fleas to be
present and active. This should not be relied on as primary control methods.
Besides the fox, dingo, cat and dog, there are a number of avian species that prey on the rabbit
in Australia.
Movements and home range
Rabbits are most active from late afternoon until early morning.
Daily movements are generally within 150 to 200 m of the warren, but this distance can increase
during drought (up to 1500 m has been observed), or decrease during the breeding season.
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Rabbits at a waterhole within the
myxomatosis trial site on Wardang
Island, South Australia in 1938
MONITORING RABBITS AT THE HUNTER WETLANDS
A very elusive rabbit at the HWC
photographed out grazing late in
the afternoon.
Different methods can be used to monitor rabbit abundance on site, HWC uses:
Spotlighting
Night-time counting, using spotlights, either on foot or from vehicles, has been used for
many years to survey animal species such as the rabbit, Oryctolagus cuniculus. This is mainly
because spotlighting is easy to do and can cover large areas in a relatively short time.
Warren counts and harbours
Estimation of rabbit abundance from warren counts has been used in Australia since the1970s, when changes in the use
of burrows were found useful for estimating changes in the number of rabbits using the burrows. Warren counts can be
as simple as counting the number of active or inactive burrow entrances and using it as an index of rabbit abundance.
Dung counts
The dung (faecal pellets) of many species is more conspicuous than the animals themselves, especially during the day in
the case of predominantly nocturnal species such as the rabbit. Counting the dung of rabbits offers a relatively easy way
of monitoring rabbits during daylight hours. Dung counting can be as simple as walking a transect and recording the
number of pellets via a 1 to 10 scale of density.
Other Rabbit Signs
Other signs of rabbits can be used to monitor rabbit activity and abundance. These signs include tracks, bait station
visitation and diggings. Counting tracks can be passive (animal behaviour is not altered by detection; e.g. by placing sand
plots across a road or track) or active (animals are attracted by a lure, e.g. by using scent and bait stations). Track
counts are used predominantly for elusive animals or those found in low densities, such as foxes and wild dogs. Track
counts using sand plots that are swept clean each day have been used successfully for rabbits where other more
commonly used monitoring techniques were not feasible and may be useful in areas where vegetation or terrain make
other counting methods difficult.
Bait stations can be used to monitor rabbit abundance by using free-feeding or toxic bait. Using free-feed stations can
indicate where ‘hotspots’ of rabbit activity are, whereas monitoring toxic bait station activity will measure the efficacy of
Monitoring
Technique
Advantages
Disadvantages
Walked
Spotlight
Counts




 Counts can be highly unreliable  Sightability can be effected by vegetation  unreliable method in wet and windy conditions
Warren
Counts
 reliable measure  indicates long-term rabbit-proneness and
 May require specialist help  warrens may be difficult to detect in sand-dune areas
 can estimate total rabbit abundance per land type  warren ripping costs can be estimated
 drought  impractical in areas where rabbits use few or no warrens
 can be done in areas where rabbits do not use
 cannot be used for some time after rain  rate of dung production varies with season and quality of
Dung Counts
Sand Plots
Quick & simple Can be done by one person Suitable for small areas Helps locate rabbit feeding grounds for poisoning
infestation during warrens  limited effect of wind, temperature, vegetation
or terrain  flexible timing of sampling and can be done
during the day
 flexible timing of sampling and can be done
diet  not an accurate measure of absolute numbers but good
for assessing relative numbers
 sign may be destroyed by weather or human and vary
during the day
seasonally  not an accurate measure  long set-up time  not always appropriate for use with rabbits
Non-toxic Bait
Stations
 flexible timing of sampling and can be done
Diggings
 quick and simple  flexible timing of sampling and can be done
 sign may be destroyed by weather or human and vary
during the day
seasonally  not an accurate measure  long set-up time
 sign may be destroyed by weather or human and vary
seasonally  not an accurate measure
during the day
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control programs. Bait stations are portable and can be moved from one site to another as needed. However, a
drawback to using bait stations is that relatively large proportions of rabbit populations are reluctant to enter bait
stations. Counting the number of rabbit diggings or scratchings along a standardised walk transect will also give an idea
of abundance.
Monitoring methods, eg.: Sand plots; Non-toxic bait stations; Diggings; Live trapping; Warren trapping of live rabbits, see
table page 2.
RABBIT CONTROL
Integrated rabbit management
Optimum control of rabbits is best achieved by integrating more than one control method. Reliance on a single control
method will most likely lead to ongoing problems. HWC needs to understand the rabbit problem on their grounds, and
then develop an integrated control strategy to give an economic and sustainable control of this pest. The best returns
from rabbit control mainly come from a regional approach involving neighbours working together.
Warren and harbour destruction
The best way to control rabbits long-term, is to destroy their warrens and hiding places. This means that they cannot
survive the hot summers, and cannot rear their young successfully. Rabbit populations usually take many years to
recover from a thorough warren destruction program. Recovery will even take longer if the ripped warrens are
regularly checked and follow-up work done when needed.
Successful warren destruction programs rely on working out the extent of the rabbit problem by surveying the area for
signs of rabbits, e.g. active rabbit warrens, with holes that are obviously being used, especially the doe’s strenuous hole
cleaning just before she gives birth. This leaves a streak of dirt which is often visible for some distance. Other signs are
fresh rabbit droppings, and chisel-shaped teeth marks on food plants.
Before taking to the area with a tractor and ripper, proper planning can save time and effort. Marking all of the warrens
will save valuable time. Obviously this part of the job is very labour intensive. GPS technology is an invaluable aid to
planning the most efficient way to cover all warrens in an area.
Usually the best time of year to destroy rabbit warrens is in the late summer, when rabbit numbers are already low and
the soil is dry and will collapse more easily.
Effective ripping of warrens relies on deep ripping with close ripping lines and the ripping extending past the warren.
Ideally, the ripper tines should be to a depth of 900mm, at a spacing of 500mm. After ripping one way it should be
repeated at 90°, this process is known as cross-ripping.
Particular equipment may be useful for particular jobs. To protect native vegetation, a single ripper tine on a front end
loader or a backhoe can do the trick. Blade ploughs may be adequate for light or loamy soils, and disc cultivators may be
successful in cultivated areas where rabbit numbers are low.
Poisoning
1080
The most commonly used poison to control rabbits is sodium monofluoracetate,
commonly known as 1080. 1080 must only be used under the supervision of a
qualified operator. Interestingly, many native plants, have naturally high levels of 1080,
and some native animal and bird species have a resistance to 1080.
Pindone©
Is a anticoagulant compound which acts in a similar way to common rat poisons. Pindone© can be used where 1080
cannot be used. Pindone© also has an effective antidote, which is not the case for 1080.
These poisons are not to be used lightly. If they are used incorrectly, native mammals and birds, livestock, pets and even
humans can be at risk. In addition, careless use can lead to the poison being ineffective, particularly through rabbits
developing resistance to the poison, or even becoming shy about eating the bait - bait-shyness.
Both the effectiveness and selectivity of poisoning rabbits are enhanced by pre-baiting with non-poisoned bait and
ensuring that only rabbits are taking the bait; using bait that is most attractive to rabbits; use minimum concentration of
poison sufficient to kill rabbits; placing the bait in the prime feeding areas of the rabbits; and collecting the carcasses of
poisoned rabbits to prevent secondary poisoning of non-target species.
Fumigation
Fumigation is used if warrens have been re-opened after ripping, or in areas which cannot be ripped.
Static fumigation uses tablets which produce phosphine gas when damp.
Predators, parasites and diseases
One major rabbit predator, the European fox, and cats have also become feral in Australia, however, they cause
problems of its own amongst native animals and livestock. Many native raptors, such as eagles, now have rabbits as a
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large part of their diet. Generally, predation
may help slow the rate of increase of the
numbers of rabbits, but is not enough in itself to make much difference.
Biological controls are very useful, even
spectacular at times, but they are not enough
by themselves.
There is a need to integrate conventional
control methods with biological control,
especially when rabbit numbers are low, to
maximise the benefit of the biological control agents.
HUNTER WETLANDS
CENTRE
SITE PLAN
0
50
100
150m
Predator proof fences
Fences can be used to prevent re-infestation
of high-value areas, eg. farm, bush
regeneration area or a wildlife sanctuary. The
Hunter Wetlands Centre is predator fenced
on all sides except the natural Iron Bark
Creek boundary that connects us to broader
environments such as Hexham Swamp...
Whether rabbits are controlled by disease,
poisoning, warren destruction, exclusion or a
combination of these methods, the point is not how many rabbits are killed, but how many are left behind.
An 80% level of control sounds great, but given an average year, the remaining 20% of rabbits only need
one year to build up to their previous levels. A level of at least 90 to 95% control is needed to have any
long-term effect.
And, of course, an even more important point to remember is that though killing rabbits may sound inhumane, wild rabbits
are affecting the survival of native Australian plants and animals. It is our responsibility to control them. We brought the European rabbit here in the first place - they are an invasive pest.
Competition and grazing by the feral European Rabbit Ocryctolagus cuniculus was listed as a Key
Threatening Process on Schedule 3 of the Threatened Species Act 1995.
Grazing and burrowing by rabbits can cause massive erosion problems, reduce recruitment and survival of native plants, and
alter landscapes. Rabbits threaten the survival of a number of native animal species by altering habitat, reducing native food
sources, displacing small animals from burrows and attracting introduced predators such as foxes.
At the Hunter Wetlands Centre it has been observed that the reduction in the number of foxes has led to an increase in the
number of rabbits, which in turn has altered the habitat for several species of birds and animals. For example through grazing
competition rabbits compete for food with the native Bandicoot.
There has been extensive revegetation of the site over many years, and recently it has been noticed that new plantings of
nursery propagated plants are ideal food for rabbits, who do major damage to new plantings which have to be
replaced,
which is a costly exercise for the HWC.
Volunteers interested in participating in this project please contact the site manager
Paul Trute in person at the Hunter Wetlands Centre office or email:
[email protected]
References:
NSW Dept. of Primary Industries, Monitoring Techniques for Vertebrate Pests Rabbits Bruce Mitchell & Suzanne Balogh.
Hunter Wetland Centre
Off the roundabout, Sandgate Road, Shortland NSW 2307
Photos: Wikipedia & HWC
PO Box 292, Wallsend NSW 2287
Ph: 4951 6466 Fax: 4950 1875
Email: [email protected]
This project was made possible with the assistance of the Hunter-Central Rivers Catchment Management
Authority using funding from the Australian Government's Caring for our Country
Web: www.wetlands.org.au
Open 9am to 4pm - 7 Days
Spoonbill Cafe: [email protected]
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