Comparison of Helicopter Line Transects with Walked Line Transects for Estimating Densities of Kangaroos

In: Wildlife research, Band 24, Heft 4, S. 397

Abstract

The performance of helicopter surveys for estimating population densities of
red kangaroos (Macropus rufus), eastern grey kangaroos
(Macropus giganteus) and common wallaroos
(Macropus robustus) was investigated by comparing
line-transect density estimates obtained from helicopter surveys with those
from ground (walked) surveys. Comparisons were made at four sites in central
western Queensland (areas with high densities of red kangaroos and common
wallaroos) that were surveyed during winter and summer from December 1991
until February 1995, and one site in south-eastern Queensland (an area of high
eastern grey kangaroo density) surveyed annually during autumn from March 1991
until March 1994. Helicopter surveys generally recorded lower sample sizes
than did ground surveys (means ± s.e = 34 ± 6%, 33
± 9% and 76 ± 2% lower for red kangaroos, eastern
grey kangaroos and wallaroos, respectively). Density estimates obtained from
the helicopter surveys were not significantly different from those obtained
from ground surveys for both red and eastern grey kangaroos as assessed by
repeated-measures ANOVA and regression analysis. However, helicopter surveys
of common wallaroos consistently returned density estimates about half those
of ground surveys. The relationships between the two methods did not differ
between winter and summer for any species. The conventional aerial survey
method for kangaroos of strip transects from fixed-wing aircraft has limited
ability to adjust for varying sightability conditions. Therefore, helicopter
surveys with line-transect sampling are an attractive alternative.