The next most significant disturbance factor after habitat destruction and fragmentation was habitat invasion by feral animals.
Only four species were considered; rabbits, foxes, cats and pigs. Nonetheless, these four are regarded as the most significant contributors to biotic impoverishment mediated through habitat destruction, competition and predation; eg Newsome (1994).
The assessment of the current and future threat of all four species was based on determining the relative distribution of each landcover type within four mapped levels of feral animal density: none, low, medium, high. In a similar manner to tenure vulnerability discussed above, the three levels of feral vulnerability were based on the mean of the sum of the products of proportional area (%) and density class (0-3). The range of this numeric was 0-100, and the thresholds used were low (< 25, *), moderate (25-50, **) and high (> 50, ***). The respective scores for all four feral species are set out in Table 16.
Landcover Rabbits Cats Foxes Pigs __________________________________________________________________ xTML4 * ** * ** eTML3 ** ** ** * wTML3 ** ** ** ** xTML3 ** ** ** ** eM2 ** ** ** * xM2 ** ** * * eL2 ** ** ** ** wL2 * *** * ** xL2 ** *** ** * eM1 * ** * *** eL1 ** *** ** ** wL1 * *** * * xL1 ** *** * * wS3 ** ** * * xS3 ** ** *** * eS2 ** ** *** * wS2 ** ** ** * xS2 ** ** *** * eS1 ** ** * * wS1 *** *** *** * xS1 ** ** * * xZ3 * ** * * xZ2 *** ** * * wZ1 ** ** ** * xH2 *** ** ** * xG4 ** *** * * xG3 ** ** * * xG2 * ** * *** Littoral * *** * ** xG1 * *** * ** xF1 * ** * **
