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

Its original habitat on the mainland “included” Austrodanthonia, Austrostipa, Poa labillardieri and Themeda triandra grasslands
and it requires dense ground cover for shelter, and open areas with relatively short grass in which to forage (Brown et al. 1991 p.
150). Replacement of native grasses by exotic pasture grasses and weeds has reduced protective cover, but other factors
including habitat destruction, predation by introduced vertebrates and exotic disease appear to be of much greater importance
than weeds in its decline (Brown et al. 1991, Backhouse and Crossthwaite 2003). One important factor is probably soil
compaction by bovid livestock (Brown 1987). It was last recorded in South Australia nearr Mt Gambier in 1890 (Aitken1983).
Several colonies possibly still existed in the Victorian Western District in the late 1940s but it probably survived only in the
Hamilton and Penshurst districts in the 1960s (Brown 1987). From c. 1971 the last remaining wild population on mainland
Australia continued to exist in a highly modified environment “almost totallydominated by exotic plant species” at Hamilton
rubbish tip, being able to escape predation by hiding in old car bodies and thickets of gorse Ulex europaeus L., and foraging in
surrounding paddocks (Backhouse and Crossthwaite 2003 p. 3).
Hadden (2002) surveyed 24 remnant grassland sites on the Victorian Western Volcanic Plains and Northern Plains by pitfall
trapping and systematic and opportunistic searching from January 1995 to February 1996. She evaluated habitat by measuring
cover of cool- and warm-season perennial grasses, native herbs, exotic grasses, exotic herbs, bare ground, dry litter, total floristic
composition (native/exotic), sheep grazing pressure and invertebrate richness. Three mammal species were captured in c. 7500
trap nights. Sminthopsis crassicaudata (Gould) was found at all sites in the Northern Plains and 7 of 12 sites in the Western
Plains. One inidividual of the Common Dunnart S. murina (Waterhouse) was captured at a Western Plains site, the first Victorian
grassland record. The introduced House Mouse Mus musculus L. was found at 5 of the Western Plains sites and 8 Northern
Plains sites. Rabbits O. cuniculus and European Hare Lepus capensis were almost ubiquitous in Northern Plains sites but were
observed at approximately half the Western Plains sites. No mammals were recorded at five of the Western Plains sites. S.
crassicaudata was abundant at some floristically rich sites and also in degraded remnants and exotic pastures. It was relatively
more abundant at sites that were lightly grazed, at sites with more open vegetation and floristically rich sites. It is an active
hunter, mainly of invertebrates, and may require open areas for foraging, as well as tussock cover as a protection from predators.
It was found living in rock piles and stone walls, and utilised wolf spider burrows on the Northern Plains. This species has
disappeared from grasslands near Melbourne where it was once common. The almost ubiquitous M. musculus was relatively
more abundant on heavily grazed sites, was absent from lightly grazed sites on the Western Plains, was more abundant at densely
vegetated sites on the Western Plains and lightly vegetated sites on the Northern Plains, and was more common on floristically
poor sites. Two other species, the introduced Brown Rat Rattus norvegicus (Berkenhout) and native Swamp Rat R. lutreolus
(Gray) have been recorded in Victorian grasslands in recent historical times.
Mus musculus is a threat to some grassland plants. Mouse predation of tubers of Diuris fragrantissima is believed to have been
responsible for mortality of perhaps 70% of plants at its single extant site during the mid-1980s (Webster et al. 2004).
The Short-beaked Echidna, Tachyglossus aculeatus (Shaw), occurs widely in grasslands (Menkhorst 1995c) but appears to be
absent from most of the smaller remnants, particularly in areas of closer settlement.
The highly depauperate mammalian faunas or remnant grasslands means that biodiversity components directly dependent upon
mammalian activities are also threatened or lost. Obvious dependents include dung beetles (Scarabaeidae: Scarabaeinae and most
Aphodiinae) that require a dung resource, and a range of ectoparasites (fleas, etc.) and endoparasites (Nematoda, etc.) that
require their host for survival. The complex consequences of the loss of native grazing species and mammalian plant-predators
have only recently begun to be explored and very little is known about the ramifications. However absence of soil disturbance by
mammals has probably had a strong negative impact on regeneration of many native forbs (Reynolds 2005) and the dispersal
opportunities for plant seeds must have been radically altered.
Birds
Few Australian birds are restricted to grasslands and by necessity they are ground-nesting species. In New South Wales,
populations of many grassland species that forage and nest on the ground have disappeared or shrunk to very low levels (Keith
2004). In Victoria the most significant regions for threatened bird species include the Northern Plains and the Wimmera Plains,
and few threatened species occur in the Western Volcanic Plains or the Gippsland Plains (Robinson 1991). Threatened birds in
Victoria are more likely to be woodland or grassland species that are seed eaters or vertebrate predators, and to nest in tree
hollows or on the ground (Robinson 1991). A number of species once common in native grasslands have declined markedly or
disappeared from grasslands as the area of habitat has shrunk, however only two species that are more or less restricted to
grasslands have endangered status (Table 16).
Table 16. Endangered bird species of south-eastern Australian temperate native grasslands. U = unlisted,V= vulnerable, E =
endangered, CE = critically endangered, T = threatened, X = extinct.
Species Common Name ACT NSW SA Vic References
Ardeotis australis(J.E. Gray) Australian Bustard X CE Sharp and Shorthouse 1996, Venn and
Menkhorst 2003, Department of Sustainability
and Environment 2009a
Pedionomus torquatus (Gould) Plains Wanderer X V/T Baker-Gabb 2003, Department of Sustainability
and Environment 2009a
Emus Dromais novaehollandiae (Latham) were once common in the Victorian basalt plains (Sutton 1916-1917, Coutts 1982)
and the grasslands of NSW (Keith 2004). Marshall (1968 p.76) reported observations by the Rev. James Backhouse in 1837 that
emus in the Melbourne area were then “fast retiring before the white population and their flocks and herds”. They are now rarely
reported on the volcanic plains (Lunt et al. 1998) and have disappeared or markedly declined in NSW grasslands (Keith 2004),
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