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

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Approved NSW <strong>Recovery</strong> Plan Brush-<strong>tailed</strong> <strong>rock</strong>-<strong>wallaby</strong><br />

Norris and Belcher (1986) suggest <strong>the</strong>re was once a nomadic group <strong>of</strong> BTRWs moving along <strong>the</strong><br />

Snowy River Gorge.<br />

6.6 Population structure<br />

6.6.1 Total population number<br />

The total population <strong>of</strong> BTRWs in Australia is thought to be between 15,000 and 30,000<br />

animals. This is a significant reduction from previous numbers, as during <strong>the</strong> period BTRWs<br />

were hunted, more than 50,000 animals were shot in one region alone. It is estimated that 10,000<br />

to 25,000 or more BTRWs in <strong>the</strong> Nor<strong>the</strong>rn ESU, 500 to 1000 BTRWs in <strong>the</strong> Central ESU, and<br />

less than 10 BTRWs in <strong>the</strong> Sou<strong>the</strong>rn ESU remain in <strong>the</strong> wild.<br />

6.6.2 Natural and human induced fluctuations<br />

Climatic modelling has been used to investigate possible past changes in <strong>the</strong> distribution <strong>of</strong><br />

BTRWs (Cavanagh unpub.). This work suggests that under past climatic extremes, a retraction in<br />

<strong>the</strong> sou<strong>the</strong>rn part <strong>of</strong> <strong>the</strong> species’ range may have occurred, and that <strong>the</strong> extension <strong>of</strong> BTRWs into<br />

<strong>the</strong> south-west <strong>of</strong> <strong>the</strong>ir range, that is, into <strong>the</strong> Grampians in Victoria, may have occurred within<br />

<strong>the</strong> last 10,000 years. This work also suggests that past climatic extremes may have helped to<br />

determine <strong>the</strong> development and distribution <strong>of</strong> <strong>the</strong> ESUs, and resulted in changes in relative<br />

abundance across <strong>the</strong> species’ range.<br />

A climate and terrain modelling program was used to investigate correlations between extinct<br />

and extant sites (Bugg 1994). This study concluded <strong>the</strong>re are fundamental bioclimatic<br />

differences between sites <strong>for</strong>merly and currently occupied by BTRWs in south-eastern Australia,<br />

and <strong>the</strong>re<strong>for</strong>e a bioclimatic basis <strong>for</strong> <strong>the</strong> decline <strong>of</strong> BTRWs in recent years.<br />

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