Twenty-one surveys have been conducted using a Cessna 182 in the pastoral zone of South Australia, covering the twenty year period 1978 to 1998, flying the same transacts and using the same method. Considerable attention has been given to observer training and the turnover rate of observers has been low. The same pilot has flown all surveys. The pastoral zone is bounded in the north and west by a dingo-proof fence. Large lakes and areas of terrain above 2000 ft elevation (notably the Flinders Ranges) were excluded from the survey, leaving a surveyed area of approximately 207 000 km2. Surveys are conducted each year in July/August, with morning and afternoon survey sessions. Transects run east/west and are 15 nautical miles (28 km) apart. The method has followed what has become the standard for fixed-wing surveys: a height of 250 ft (76m) above ground (AGL), a ground speed of 100 knots (185 km h-1), 5 km unit lengths (97 sec.) with a 7 sec. pause between each and animals counted in 200 m wide strips each side of the aircraft, demarcated by streamers attached to the wing struts. A radar altimeter is used to maintain height above the terrain and, since 1989, a global positioning system has been used to ensure adherence to the transact and to maintain the required groundspeed. Red kangaroos, western grey kangaroos, common waflaroos, emus and goats are counted and other macro fauna noted (camels, horses, dingoes, ostriches, etc.). Standard correction factors have been applied throughout, except that, in the present paper, the data are recalculated to reflect the outcomes of this workshop concerning a move to modified correction factors. The results have highlighted the responsiveness of kangaroo populations to rainfall and pasture availability. There has been a statistically significant long-term trend towards higher numbers of western grey kangaroos in the study area, and a similar trend in reds since the end of the 198211983 drought. Over the 20 years, however, there has been no statistically significant trend to either higher or lower numbers of red kangaroos. Some analyses of the data obtained by aerial survey have already been presented and, in due course, further analyses will be presented elsewhere. Importantly, the results provide a useful demonstration that long-term harvesting can be carried out without detriment to the populations.
Aerial survey of kangaroos in South Australia 1978-1998: a brief report focusing on methodology
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G. C. Grigg, L. A. Beard, P. Alexander, A. R. Pople, S. C. Cairns; Aerial survey of kangaroos in South Australia 1978-1998: a brief report focusing on methodology. Australian Zoologist 1 June 1999; 31 (1): 292–300. doi: https://doi.org/10.7882/AZ.1999.030
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