Abundane of macropods in north-eastern New South Wales, and the logistics of broad-scale ground surveys

Abstract

A broad-scale ground survey of macropod abundance in north-eastern New South Wales was undertaken in 1989-90. The survey area was stratified into an eastern and western region, and within regions by habitat on the basis of vegetation and topographic criteria. Macropod density in each stratum was estimated from walked line transect counts for five species: Macropus giganteus, Macropus robustus, Macropus parryi, Macropus rufogriseus and Wallabia bicolor. Within sampled strata, macropod density was substantially higher in the western region than in the eastern region. Macropus parryi occurred in only trace numbers in the eastern region, with the number of sightings too small for reliable density estimation. No M. parryi were sighted in the western region. Macropus giganteus and M. rufogriseus were the dominant species in sampled strata in the eastern region, while M. giganteus and M. robustus were dominant in the west. Overall, pre-survey activities of habitat digitising and liaison with landholders required approximately the same effort as actual survey work. Liaison with landholders required relatively more time in the eastern region, where human population was higher, than in the western region. Incomplete coverage of planned transect routes, due mainly to impenetrable vegetation, lead to a positive bias of no more than 10-20% in population estimation for M. giganteus and M. robustus, and an unknown bias for the other species. The use of broad vegetation information on 1 : 100 000 map sheets for habitat stratification limited the scale at which analysis of sightability could be undertaken. Macropus giganteus and M. robustus are commercially harvested in the western region. Annual commercial harvest rates in the three years prior to the survey were conservatively estimated to be less than 0.9% for M. robustus and less than 5.4% for M. giganteus.