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European Rabbits in Arid Rangelands of NSW (Arid zone (biotic factors…
European Rabbits in Arid Rangelands of NSW
European rabbit (Oryctolagus cuniculus)
most destructive pest
3/4 of NSW inhabited
inhabit 70% Aus.
approx. 200 million
introduced species
First Fleet 1788 -> domesticated livestock
Arid zone
short grasses, natural grasslands, deserts
infertile soils, unpredictable rainfall
drought resistant shrubs --> saltbush, spinifex
fails to restrict rabbit growth
abiotic factors
little rainfall
<508mm rain/year
organisms must be able to survive w/o water for long time
e.g. cacti store in stems
groundwater far below surface
temp.
temp. fluctuations in 24hrs
little moisture -> no insulation of humidity&clouds
hot day, cold night
light
lots of sun b/c no clouds/trees
adapt to overexposure
biotic factors
water conservation
underground burrows -> insulate
thick hair/feathers -> insulate
annual
germinate&grow (rainy)
makes seeds&die (dry)
introduced predators -> declining prey -> declining food
e.g. Sturt National Park (NSW)
ecological niche
highly adaptive + reproduce quickly = rapid recolonisation
live in underground warrens
key to success
refuge for natives&predators
aggressive nature
moisture from plants they eat
5+ litters/year -> 4-8 offspring at a time
if rabbits removed
less competition for food
less predation from cats&foxes
adaptations
long ears -> detect faint sounds
eyes high on side of head + flexible neck = detect predators
fur colour blends with ground -> molting
strong/flexible legs -> 16m/s
cecum (digestive track) -> nutrients from whole plant
eat+disperse seeds
impacts
fauna
decline & disappearance in native species in arid NSW
vulnerable
Greater Bilby
Hairy-nose wombat
Plains-wanderer
Mallee fowl
extinct
Yellow-footed rock wallaby
Golden bandicoot
How? -> compete for food; degrade vegetation; compete for burrows
native animals don't survive b/c resources taken over
medium-sized mammals
e.g. desert bandicoot, lesser bilby
extinct last 200 yrs
rabbits invaded habitat
soils erosion
excessive grazing -> land loss
key threat
Environment Protection & Biodiversity Conservation Act
Threatened Species Conservation Act 1995
warrens -> land degredation
topsoil loss -> no above/below ground vegetation
flora
reduce regeneration of native plants
ring-barking, grazing
1x rabbit per 2x hectares
eat seeds&seedlings
replace w/ unpalatable weeds
eat so many plants -> no food for them or others
balance
introduced species susceptible to different pressures
impact 304 species plant/animal
overgrazing -> loss plant biodiversity
selective pressures
biotic
predation
attract & provide food for other introduced predators
indirectly impacts native animals b/c predators eat them too
dingoes, foxes, cats
Australia lost more mammals than any other
rabbit part of raptor diet
slows population growth -> not much difference
disease
disease didn't kill all off
over time adapted to resist viruses
pass on characteristics to offspring
RHDV (Rabbit Haemorrhagic Disease Virus)
1995
reduced by 98% -> dryer regions
Myxoma virus (myxomatosis)
1950s -> 1st biological control agent
reduced populations by 90%
developed resistance
still accounts 25% control -> arid zones
Human impacts
trapping
shooting
uneffective
breed quicker than killed
poisoning
warren-ripping
can't survive heat; can't raise offspring
many years to recover
rabbit-proof fencing
National Parks & Wildlife Service (NPWS)
few predators & diseases; high reproduction
populations haven't naturally diminished
less danger
env'mt suited to rabbits = thrive & survive
factors in native habitat kept control -> Aus. predator lack & good reproductive climate = increased populations
absence of biological controls
competition
some organisms able to survive/reproduce -> others can't compete for resources
abiotic
soft soil for burrowing
= shelter opportunities to mate & survive
water availability
water gained through plant roots
climate
perfect for reproduction