Literature review: Impact of Chilean needle grass ... - Weeds Australia

of destruction as vermin and partly from extinction of its tussock grassland habitat (Seebeck and Rose 1989). Bettongs were
considered to be agricultural pest species during early European settlement (Seebeck and Rose 1989, Noble et al. 2007).
Wakefield (1964a p. 277) listed other species found as subfossils in caves near Byaduk and Mt Eccles that are not found in the
Western Plains Grasslands today but were “Presumably ... present on the basalts of south-western Victoria at the time of
European occupation ...”. These included the extinct Pseudomys auritus which was present “in the recent past ... eastward,
apparently in abundance, to central Victoria” (Wakefield 1964a p. 278) and was “once widespread in western Victoria”
(Wakefield 1963b p. 44).
Perhaps at a more distant time the Western Basalt Plains were also inhabited by the Tasmanian Devil Sarcophilus harrisii
(Boitard) and the Thylacine Thylacinus cyanocephalus (Harris). Wakefield (1963a) reported sub-fossil remains of both these
large predators, extinct on mainland Australia, from lava caves at Mount Hamilton. Remains of of S. harrisii appeared to be
“quite modern” with one mandible having “pieces of dried tissue adhering to the bone”, while the few remains of T.
cyanocephalus appeared to be “not ... very old” (Wakefield 1963a p. 324). Remains of the latter species are known also in
Victoria from Gisborne, while remains of S. harrisii in Victoria have been radiocarbon dated to 550 ±200 years B.P. (Wakefield
1963a). Dixon (1989 p. 557) noted that T. cyanocephalus was well known from the main area of natural open grasslands in
Tasmania, the midland plains region, and that most captures of the animal occured in “farmed flat areas”, where it was
considered a serious predator of lambs. Loss of ‘top predators’ has serious cascade effects in food webs, and probably
contributed greatly to the collapse of grassland ecosystems.
Bandicoots are primarily nocturnal and crepuscular, rat to rabbit sized marsupials, which, along with bilbies (Thylacomyiidae)
have sufferred more negative impact from European occupation than any other marsupial group except Potoroidae (Brown 1987)
and the thylacine. The extinct Pig-footed Bandicoot Chaeropus ecaudatus (Peramelidae) was a grassland species which required
“lush growing tips of grasses and herbs”, so livestock grazing is probably the major factor in its extinction (Menkhorst 1995a)
along with habitat destruction by rabbits and predation by introduced mammals (Seebeck and Mansergh 2003). Seebeck and
Mansergh (2003), on the other hand, considered it to be an arid zone species, restricted in the historical period in Victoria to the
Mallee. Sheep grazing is also probably the major factor in disappearance of the Bridled Nailtail Wallaby (Menkhorst 1995a).
Losses of such a large proportion of the native herbivores likely had a profound effect on plant diversity (Bloomfield and
McPhee 2006).
Studies of more arid and northern regions of/Australia, and other areas of the temperate pastoral zone show similar losses of
medium sized (35 g to 55 kg) ground dwelling marsupials and murid rodents (Burbidge and McKenzie 1989, Short and Smith
1994, Short and Turner 1994, Noble et al. 2007). Various factors in combination are blamed including hunting, increased
predation from foxes and cats, rabbit and livestock grazing, habitat clearance and fragmentation, land use change and altered fire
regimes (Recher and Lim 1990, Short and Smith 1994). Rat kangaroos (Potoroidae) never recovered from hunting under a
bounty system on the Northern Tablelands of NSW (Johnson and Jarman 1975), although they were present “in plague
proportions” in the 1880s and 1890s (Cameron 1975 p. 21). Altered fire regimes are possibly the most important: in areas where
it has been possible to study the losses, in Central Australia, they are temporally correlated with the departure of aboriginal
people and the cessation of regular aboriginal burning (Short and Turner 1994, Flannery 1994). The absence of regular burning
resulted in decreased rates of nutrient recycling and the absence of new lush vegetation, creating a nutritional crisis for the more
specialised feeders (Flannery 1994). A general increase in biomass of vegetation coupled with decreased patchiness meant that a
fire, when it did arrive, burnt much more widely and intensely than previously, creating large areas with no food, nor shelter
from predators, and later a uniform, even-aged vegetation (Flannery 1994). However a test of the mosaic burning decline
hypothesis (Short and Turner 1994) found that mosaic scale had no significant effect on survival of three species in the critical
weight range, and that declines on mainland Australia and survival on off-shore islands was better explained by the presence or
absence of exotic predators (foxes and cats) and herbivores (rabbits and livestock). More generally, Burbidge and McKenzie
(1989) found that the diverse effects of diversion of environmental production to human uses effectively resulted in a general
trend to environmental aridity, that differentially affected moderately sized mammals with limited mobility, relatively high daily
metabolic requirements and more specialised feeding strategies.
Victorian grasslands now support little native mammalian diversity. Victorian mammals adapted to grasslands and grassy
woodlands are one of Menkhorst’s (1995b) five groups of mammals requiring specific managment to secure their future. They
include the Fat-tailed Dunnart Sminthopsis crassicaudata (Gould), Eastern Barred Bandicoot Perameles gunnii and Common
Wombat Vombatus ursinus. The latter occurred throughout the volcanic plains in the 1800s but is now extinct in western
Victorian grasslands. Another widespread species not threatened on a State or national basis, the Eastern Grey Kangaroo
Macropus giganteus was once common in the Victorian basalt plains (Sutton 1916-1917, Coutts 1982) but is now rare in the
region (Lunt et al. 1998) although some large populations exist (e.g. at Woodlands Historic Park). In the South East of South
Australia it was restricted to four colonies by 1983, one in woodland with associated grassland (Aitken 1983). The Western Grey
Kangaroo M. fuliginosus (Desmarest) was still common and included grassland in its habitat (Aitken 1983). This species prefers
areas with heathy understorey but forages in grassland (Bennett 1995).
In the South East of South Australia S. crassicaudata was considered common in grassland, including pasture, while V. ursinus
was reduced to remnants, including populations in coastal grassland and sedgeland (Aitken 1983).
Perameles gunnii, incorrectly said to be endemic to the Victorian Volcanic Plain (DNRE 1997), was formerly widespread and
abundant across the Plains from near Melbourne north to Beaufort and west to Coleraine in Victoria and into the South East of
South Australia, but is now critically endangered on mainland Australia (Aitken 1983, Brown 1987, Brown et al. 1991,
Backhouse and Crossthwaite 2003). The mainland and Tasmanian populations are distinct, undescribed subspecies (Backhouse
and Crossthwaite 2003). P. gunnii is “specifically adpated to grassland and savannah woodland” (Brown 1987). P. gunnii digs
small conical burrows in the soil when foraging for its invertebrate prey. Earthworms are important in the diet in wetter months.
Cockroaches (Blattidae), earwigs (Forficulidae), beetles, both larval and adult especially larval Scarabaeidae, Lepidoptera larvae
and Romulea rosea bulbs are other common dietary items (Brown 1987).
144