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.

Design of aerial surveys for population estimation and the management of macropods in the Northern Tablelands of New South Wales, Australia

“…The initial helicopter surveys conducted in the three Northern Tablelands kangaroo management zones were structured around a design based on the arbitrary placement of survey transects in blocks of four transects 10 km apart within two of three strata within each zone determined on the basis of kangaroo density (Southwell et al 1995) and land use. The number of blocks of transects (each of a nominal length of 40 km) placed into each management zone was proportional to the size of the survey area within the zone.…”

“…In 1989 and1990, a series of ground surveys were conducted to estimate the densities of macropods in an area of northeastern NSW that included the three Northern Tablelands kangaroo management zones (Southwell et al 1995). In the years subsequent to this, harvest quotas for eastern grey kangaroos and wallaroos in these zones were set broadly in relation to the 1989-1990 population estimates.…”

“…This practice continued until 2001, when the first helicopter surveys of the kangaroo populations in the Northern Tablelands management zones were successfully undertaken (Cairns 2003). To have undertaken annual or regular ground surveys similar to those carried out by Southwell et al (1995) would have been logistically cumbersome and relatively costly. Furthermore, helicopter surveys conducted using line-transect sampling have been demonstrated to be an effective method for estimating eastern grey kangaroo numbers and a reasonably effective method for estimating wallaroo numbers on a small to medium scale in other parts of Australia (Clancy et al 1997;Clancy 1999;Southwell and Sheppard 2000).…”

“…The design protocols developed through the use of an automated survey design algorithm (Thomas et al 2003) and the results of the surveys conducted using these design protocols are presented and discussed in relation to the conduct and outcomes of previous helicopter (Cairns 2003) and walked line-transect surveys (Southwell et al 1995) that have been conducted in the Northern Tablelands region.…”

Genetic inference as a method for modelling occurrence: A viable alternative to visual surveys

“…Therefore, many habitats and species are not amenable to aerial surveys (Southwell et al 1997). Ground surveys, such as walked line transects can overcome the terrain and habitat issues of aerial surveys, but are time consuming (Coulson & Raines 1985;Southwell et al 1995;le Mar et al 2001). Driven line transects increase the number of transects able to be monitored and therefore survey coverage (Coulson & Raines 1985;.…”