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

The significance <strong>of</strong> fox predation upon marsupial moles is now in question (J.
Benshemesh pers. comm.), <strong>and</strong> <strong>the</strong>se mammals may prove to be common <strong>and</strong> not in
decline.
Foxes also prey heavily on <strong>the</strong> eggs <strong>of</strong> marine <strong>and</strong> freshwater turtles in Western
Australia, <strong>and</strong> in Queensl<strong>and</strong>, some nesting sites <strong>of</strong> marine turtles are baited to reduce
fox predation, but predation remains a very serious problem in Queensl<strong>and</strong> for <strong>the</strong>
following species: Fitzroy River turtle, Burnett River snapping turtle, flatback turtle
<strong>and</strong> green turtle (Sections 7). O<strong>the</strong>r rare freshwater turtles may be at risk as well, for
example <strong>the</strong> endangered Gulf snapping turtle (Elusor lavarackorum), but information
is lacking (C. Limpus, pers. comm.). Fox predation is listed federally <strong>and</strong> in New
South Wales as a threatening species, <strong>and</strong> threat abatement plans have been prepared
in <strong>the</strong>se two jurisdictions (Environment Australia [1999], NSW National Parks <strong>and</strong>
Wildlife Service [2001]).
Key papers arguing for <strong>the</strong> role <strong>of</strong> foxes in mammal losses include Finlayson (1961),
Richards <strong>and</strong> Short (1996), Short <strong>and</strong> Calaby (2001). O<strong>the</strong>r explanations for <strong>the</strong>
extinctions include <strong>the</strong> degradation <strong>of</strong> refugia hypo<strong>the</strong>sis (Morton 1990) <strong>and</strong> <strong>the</strong>
altered fire regime hypo<strong>the</strong>sis, but <strong>the</strong>se are losing credibility today, because native
mammals that live in spinifex deserts independently <strong>of</strong> refugia have disappeared, <strong>and</strong>
so too mammals from areas where Aboriginal burning was maintained.
Foxes are destructive predators partly because <strong>the</strong>y engage in ‘surplus killing’,
sometimes killing more prey than <strong>the</strong>y can eat. Short et al. (2002) document various
examples <strong>of</strong> individual foxes having killed but not eaten large numbers <strong>of</strong> rock
wallabies, bettongs or o<strong>the</strong>r prey in a short period, <strong>and</strong> suggest that this behaviour
(found also in dingoes but not cats), may help explain <strong>the</strong> rapid disappearance <strong>of</strong>
various mammals after foxes first invaded.
Despite <strong>the</strong> evidence against foxes, <strong>the</strong>re are circumstances under which fox control
may not be warranted. Culling <strong>of</strong> foxes can result in elevated numbers <strong>of</strong> rabbits
which may impose <strong>the</strong>ir own environmental cost (Banks et al. 1998). Foxes may thus
have an environmental benefit <strong>and</strong> should not necessarily be controlled at sites
supporting rare plants that are susceptible to rabbit browsing (P. Mahon pers. comm.).
But one field experiment found that foxes (<strong>and</strong> cats) suppressed numbers <strong>of</strong> rabbits
only when rabbit numbers were low because <strong>of</strong> a drought (Newsome et al. 1989).
During a run <strong>of</strong> good years rabbit populations eventually ‘escape’ <strong>the</strong> control exerted
by predators because <strong>the</strong>y can breed continuously but carnivores only seasonally
(Newsome et al. 1989).
The value <strong>of</strong> fox control on behalf <strong>of</strong> malleefowl in central Australia has been
questioned (Peter Copley pers. comm.). The main threat to malleefowl in this region
may be fire. Fox baiting (which also kills dingoes) may benefit <strong>feral</strong> cats by removing
dingoes. The value <strong>of</strong> fox baiting in <strong>the</strong> New South Wales mallee has also been
questioned (Joe Benshemesh pers. comm.).
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