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

macropods <strong>and</strong> b<strong>and</strong>icoots) within <strong>the</strong> favoured prey size <strong>of</strong> foxes. When nature
reserves are baited with 1080, which targets foxes but not cats (which usually avoid
baits), mammals such as rock wallabies, numbats, bettongs <strong>and</strong> quolls benefit greatly.
This finding has been taken as evidence that Foxes are more harmful than cats, along
with <strong>the</strong> fact that Tasmania <strong>and</strong> Kangaroo Isl<strong>and</strong>, which host cats but not foxes (apart
from a few new arrivals) have not lost any small mammals to extinction. Many <strong>of</strong> <strong>the</strong>
mammal extinctions more closely match <strong>the</strong> arrival <strong>of</strong> foxes than cats, which
preceded <strong>the</strong>m (Abbott 2002, Morris 2000, Short 1998). Fur<strong>the</strong>rmore, several dietary
studies have found that cats prey largely upon young rabbits (Potter 1991).
Cats have eliminated colonies <strong>of</strong> bilbies, burrowing bettongs <strong>and</strong> Rufous harewallabies
reintroduced to mainl<strong>and</strong> sites, sometimes thwarting whole reintroduction
efforts (Smith & Quin 1996). This is a serious problem, although it does not mean that
cats caused <strong>the</strong> original declines because <strong>the</strong> reintroduced <strong>animals</strong> were few in
numbers <strong>and</strong> naïve about predation.
However, some mammal disappearances predate <strong>the</strong> arrival <strong>of</strong> foxes <strong>and</strong> <strong>the</strong>se can
plausibly be attributed to cats, because <strong>the</strong>y also fall within <strong>the</strong> small size range
preferred by cats (up to 1 kilogram weight). They are <strong>the</strong> pig-footed b<strong>and</strong>icoot, Desert
b<strong>and</strong>icoot <strong>and</strong> golden b<strong>and</strong>icoot (Abbott 2002), <strong>and</strong> various rodents (Morris 2000)
including <strong>the</strong> white-footed rabbit-rat <strong>and</strong> several species <strong>of</strong> hopping mice. Smith <strong>and</strong>
Quin (1996) argue that cat-caused extinctions among rodents are most plausible for
species weighing up to 90 grams. However, many rodent species remain common in
regions supporting cats, <strong>and</strong> some rodents were evidently declining before cats
arrived. In a series <strong>of</strong> articles about conservation <strong>of</strong> native rodents appearing in <strong>the</strong>
journal Wildlife Research in 2000 (volume 27), various threatening processes are
canvassed but cats are not singled out as <strong>the</strong> worst threat. This does not mean <strong>the</strong>y did
not cause extinctions in <strong>the</strong> past.
The recovery plan for <strong>the</strong> endangered Julia Creek dunnart, confined to grassl<strong>and</strong>s in
north <strong>and</strong> central Queensl<strong>and</strong>, identifies predation, principally by <strong>feral</strong> cats, as a ‘key
process threatening <strong>the</strong> viability <strong>of</strong> remnant populations’ (Lundie-Jenkins & Payne
2004). The report notes:
‘An investigation <strong>of</strong> <strong>the</strong> stomach contents <strong>of</strong> <strong>feral</strong> cats revealed that <strong>the</strong>y were
a significant predator <strong>of</strong> <strong>the</strong> Julia Creek dunnart <strong>and</strong> that predation can be
locally high. It has been suggested that cats may have been responsible for <strong>the</strong>
disappearance <strong>of</strong> Julia Creek dunnarts on <strong>the</strong> Lyrian property where <strong>the</strong>y were
once readily trapped…’
However, at Bladensburg National Park, <strong>the</strong> main reserve for Julia Creek dunnarts,
cats are rarely seen, <strong>and</strong> foxes appear to pose a greater threat.
In Australia, most mammal extinctions have occurred in <strong>the</strong> sou<strong>the</strong>rn half <strong>of</strong> <strong>the</strong>
country. But many small mammals, including native rodents <strong>and</strong> b<strong>and</strong>icoots, are now
declining in nor<strong>the</strong>rn Australia, within <strong>the</strong> Kimberley <strong>and</strong> Top End (Morris 2000,
Woinarski 2000, Strahan 1998). Cats may be contributing to <strong>the</strong>se declines, although
changes in fire regimes appear to be <strong>the</strong> main cause <strong>of</strong> decline (Woinarski I 2001),
<strong>and</strong> browsing <strong>and</strong> trampling by buffalo <strong>and</strong> cattle may also pose a greater threat.
Within Kakadu National Park, where rodents are declining, cats occur in very low
numbers (J. Woinarski pers. comm.), but cats in low numbers may still pose a threat
to declining mammals. Research is needed to determine whe<strong>the</strong>r cats pose a serious
threat to <strong>the</strong> various rodents <strong>and</strong> b<strong>and</strong>icoots that are declining in nor<strong>the</strong>rn Australia.
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