Recovery plan for the brush-tailed rock-wallaby - Department of ...

Approved NSW Recovery Plan Brush-tailed rock-wallaby
A study which found massive infestations of hydatid cysts in the thoracic cavities of BTRWs
suggests a relationship between hydatidosis in BTRWs and sheep (Close 1984 in Lobert 1988).
Lobert (1988) also raised the possibility that BTRWs are susceptible to toxoplasmosis infection,
carried by cats. A BTRW in Kangaroo Valley was reported to have died from toxoplasmosis in
addition to liver fluke infestation (Eldridge pers. comm.).
Lumpy jaw was present in the captive colony at Jenolan Caves before 1988 (Buchan 1995). This
disease is more prevalent in populations of macropods which are exposed to human contact and
fed soft processed foods.
9.1.4 Competition with introduced and native herbivores
In general, the level of competition between BTRWs and other herbivores is poorly understood.
The study outlined in section 6.4 (Short and Milkovits 1990) noted that BTRW decline was most
pronounced in parts of their range where sheep grazing areas were occupied by goats, rabbits
and foxes. Although the study admitted it was hard to isolate threats, it concluded that
competition with goats and predation by foxes were the most important factors in BTRW
decline.
Competition with goats is considered partly responsible for the decline of the BTRW on rocky
habitat west of the Great Divide as shelter sites there are now occupied by goats (Short and
Milkovits 1990). Rabbits also could compete with the BTRW, particularly when food is scarce.
Although direct competition is hard to measure, Lim et al (1987) noted the presence of goats
significantly affected the recovery of yellow-footed rock-wallaby populations after drought.
Goats can compete for shelter, and Copley (1983) reported goats evicting yellow-footed rockwallabies
from caves.
Bayne (unpub.) has also observed BTRWs being flushed from sites by goats, and refuge sites
disturbed or destroyed. In its 1997 Final determination on the Warrumbungles population of
brush-tailed rock-wallabies, the NSW Scientific Committee stated that competition from goats
for shelter sites and food constituted a major threat to the Warrumbungles BTRW population,
and that competition was likely to increase during periods of drought (NSW Scientific
Committee 1997).
Goat control was undertaken in areas around yellow-footed rock-wallaby colonies in western
NSW (Sharpe 1999). Although the population was not directly monitored, numbers slowly
declined during this period. Sharpe concluded that either the goat control program had little
impact on the goat population, or competition with goats was not the major limiting factor for
the yellow-footed rock-wallaby population.
The removal of refuge vegetation may be one of the more important impacts of feral herbivores.
Many BTRW refuges, particularly in the northern rivers gorges in north-eastern NSW, consist
mainly of vegetation, and agile browsers like goats could totally destroy them (Bayne unpub.). It
is likely that the low number of suitable refuge sites is a limiting factor in the distribution of the
BTRW.
While competition with herbivores other than goats is difficult to demonstrate, the impact of
habitat alteration may be significant. For example, Pearson (1992) considered rabbits were a
major factor in altering the habitat of black-footed rock-wallabies. The effect of rabbits may be
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