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

unpalatable plants, <strong>and</strong> spread <strong>of</strong> weeds. Feral cattle are capable <strong>of</strong> <strong>the</strong> same <strong>and</strong> o<strong>the</strong>r
<strong>impact</strong>s whenever <strong>the</strong>y achieve significant densities or concentrate around a few
watering points.
Feral cattle are <strong>the</strong> most damaging <strong>feral</strong> animal in <strong>the</strong> Kimberley, where <strong>the</strong>y pose a
serious threat to <strong>the</strong> survival <strong>of</strong> monsoon rainforest remnants (McKenzie et al. 1991,
T. Start, pers. comm.). Strays from pastoral leases are w<strong>and</strong>ering along watercourses
deep into national parks where <strong>the</strong>y breed up <strong>and</strong> trample fragile riparian habitats <strong>and</strong>
vine thickets (rainforests). The vine thickets are a rare <strong>and</strong> highly significant habitat,
representing <strong>the</strong> rainforests that once occurred widely in <strong>the</strong> region when <strong>the</strong> climate
was wetter. Cattle camp inside <strong>the</strong> thickets <strong>and</strong> damage <strong>the</strong>m by browsing <strong>and</strong>
trampling (P. Mason pers. comm.). By removing all <strong>the</strong> foliage within reach, <strong>feral</strong>
cattle increase light levels <strong>and</strong> <strong>the</strong>reby facilitate invasion <strong>of</strong> rainforest edges <strong>and</strong> cattle
trackways by exotic buffel grass (Cenchrus ciliaris), o<strong>the</strong>r weeds, or native grasses,
which fuel very hot fires that kill rainforest trees. Photos <strong>of</strong> cattle damage to
Kimberley rainforest are illustrated in McKenzie et al. (1991). In surveys conducted
during <strong>the</strong> 1980s, <strong>feral</strong> cattle were found in only one <strong>of</strong> 20 vine thicket sites, but all <strong>of</strong>
<strong>the</strong> sites now have <strong>feral</strong> cattle (P. Mason pers. comm.) The early surveys recorded
small mammals in 30-40 per cent <strong>of</strong> traps; that rate has now dropped to one or two per
cent. Feral cattle <strong>and</strong> inappropriate fire regimes are toge<strong>the</strong>r destroying this rare
habitat type (P. Mason) <strong>and</strong> <strong>the</strong> fauna it contains. McKenzie et al. (1991) express
concerns that cattle (both <strong>feral</strong> <strong>and</strong> domesticated), by degrading large numbers <strong>of</strong>
Kimberley rainforest patches, pose a threat to rainforest l<strong>and</strong> snails, spiders, reptiles
<strong>and</strong> birds. O<strong>the</strong>r <strong>feral</strong> <strong>animals</strong> are scarce or non-existent in <strong>the</strong> sites where Kimberley
rainforests grow.
In Purnulu (Bungle Bungle) National Park, damage from <strong>feral</strong> cattle was found to be
severe during a survey reported in 1992. Woniarski (1992) noted ‘p<strong>and</strong>anus thickets
along sections <strong>of</strong> <strong>the</strong> Ord River have been extremely degraded by cattle trampling,
erosion <strong>and</strong> <strong>the</strong> spread <strong>of</strong> exotic plants (e.g. Cenchrus spp. Parkinsonia).’ Most <strong>of</strong> <strong>the</strong>
cattle have since been removed.
In Lakefield National Park, <strong>feral</strong> cattle overgraze <strong>and</strong> degrade <strong>the</strong> riparian systems (J.
Clarkson, pers. comm.), which are critical for wildlife. The cattle are difficult to
control because <strong>the</strong> l<strong>and</strong>scape is remote <strong>and</strong> difficult to access. Management problems
are compounded by <strong>the</strong> large numbers <strong>of</strong> domestic cattle grazed in this national park.
Many <strong>of</strong> <strong>the</strong> <strong>feral</strong> cattle are mustered under contract to nearby graziers.
In Barlee Range Nature Reserve in Western Australia, a clay pan supporting sensitive
vegetation was fenced against <strong>feral</strong> cattle, Donkeys <strong>and</strong> stray cattle, but mainly to
exclude <strong>feral</strong> cattle. The vegetation improved dramatically (P. Kendrick pers. comm.)
In Forty Mile Scrub National Park in north Queensl<strong>and</strong>, Fensham et al. (1994) found
that <strong>the</strong> presence <strong>of</strong> billygoat weed inside dry rainforest was strongly correlated with
damage by <strong>feral</strong> cattle. Dry rainforest has very high conservation values.
In Kakadu National Park, small herds <strong>of</strong> <strong>feral</strong> cattle are valued by <strong>the</strong> traditional
owners as a meat source (A. Ferguson pers. comm.). The <strong>impact</strong> <strong>of</strong> <strong>the</strong>se cattle on
conservation values have not been assessed but appear to be minor compared with <strong>the</strong>
<strong>impact</strong>s <strong>of</strong> horses <strong>and</strong> <strong>the</strong> likely <strong>impact</strong>s <strong>of</strong> burgeoning numbers <strong>of</strong> <strong>feral</strong> buffalo.
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