Review of the management of feral animals and their impact on ...

RHD (previously known as rabbit calicivirus), has greatly reduced rabbit numbers
throughout <strong>the</strong> Rangel<strong>and</strong>s, <strong>and</strong> in most regions native vegetation is responding
dramatically. (The <strong>impact</strong> <strong>of</strong> RHD is reported in various papers appearing in a special
issue - volume 29 [6]) - <strong>of</strong> Wildlife Research). But in South Australia, within <strong>the</strong>
Flinders <strong>and</strong> Gammon Ranges, mulga is failing to regenerate in <strong>the</strong> presence <strong>of</strong> very
low numbers <strong>of</strong> rabbits (R. Henzell, pers. comm.). There has been very little if any
regeneration <strong>of</strong> mulga within <strong>the</strong>se regions since rabbits entered in <strong>the</strong> nineteenth
century (G. Mutze pers. comm.). Mulga is a major habitat for wildlife in arid
Australia <strong>and</strong> this lack <strong>of</strong> regeneration is a serious concern. Mulga woodl<strong>and</strong> in
Western Australia, <strong>the</strong> Nor<strong>the</strong>rn Territory <strong>and</strong> Queensl<strong>and</strong> is regenerating, <strong>and</strong> this
problem appears to be confined to South Australia <strong>and</strong> New South Wales, where
mulga seedlings, under a regime <strong>of</strong> low summer rainfall, grow very slowly <strong>and</strong>
remain vulnerable to rabbit predation for many years. (In mulga woodl<strong>and</strong> in o<strong>the</strong>r
states Rabbits are also more patchily distributed, especially in <strong>the</strong> north <strong>of</strong> <strong>the</strong>ir range
where hot summers limit <strong>the</strong>ir range). In western New South Wales problems are
evident outside <strong>the</strong> mulga zone as well. In Kinchega National Park very little
recruitment <strong>of</strong> plants is occurring, <strong>and</strong> suckers produced by four species (Acacia
carneorum, Alectryon oleifolius, Casuarina pauper <strong>and</strong> Santalum acuminatum) are
not surviving browsing, leading Denham <strong>and</strong> Auld (2004) to conclude that ‘<strong>the</strong>
probability <strong>of</strong> successful recruitment into populations <strong>of</strong> suckering species in western
New South Wales continues to be low even at very low rabbit densities’. In New
South Wales <strong>the</strong> situation is compounded by large number <strong>of</strong> goats <strong>and</strong> kangaroos
which contribute greatly to total browsing pressure. The problem <strong>of</strong> rabbits preventing
regeneration is considered fur<strong>the</strong>r in Section 7.1.8.
Rabbits are an important food for native birds <strong>of</strong> prey. A study around Mildura found
that young rabbits were <strong>the</strong> staple food (60-92 per cent by weight) <strong>of</strong> wedge-tailed
eagles, goshawks, harriers, kites <strong>and</strong> falcons (Baker-Gabb 1984). Similar results have
been reported in o<strong>the</strong>r studies. Rabbits are also a major source <strong>of</strong> food for foxes <strong>and</strong>
cats, with <strong>the</strong> latter targeting rabbit kittens. One study in western New South Wales
found that rabbits made up 45 per cent <strong>of</strong> fox diets <strong>and</strong> 54 per cent <strong>of</strong> cat diets
(Catling 1988). When RHD spread across Australia <strong>the</strong>re were concerns that native
birds <strong>of</strong> prey would decline dramatically, <strong>and</strong> that abundant foxes <strong>and</strong> cats, deprived
<strong>of</strong> <strong>the</strong>ir main prey, would exact a heavy toll on rare native fauna. Since <strong>the</strong> spread <strong>of</strong>
RHD <strong>the</strong>re have been some declines in birds <strong>of</strong> prey but not to a serious extent. Rare
native species are not known to have suffered from increased fox <strong>and</strong> cat predation.
Holden <strong>and</strong> Mutze (2002) found that foxes ate more insects <strong>and</strong> carrion after rabbit
numbers dropped, <strong>and</strong> both fox <strong>and</strong> cat numbers decreased substantially after RHD
went through.
Table 7 Species listed in <strong>the</strong> rabbit Threat Abatement Plan (1999) for which rabbits
are a known or perceived threat.
Known threat
Scientific name Common name
Mammals
Macrotis lagotis Greater Bilby
Plants
Caladenia gladiolata Orchid
Thesium australe Austral toad-flax
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