Transect width and missed observations in counting muskoxen (Ovibos moschatus) from fixed-wing aircraft

  • P. Aastrup Greenland Environmental Research Institute. Tagensvej 135, 4, DK-2200 Copenhagen N, Denmark
  • A. Mosbech Greenland Environmental Research Institute. Tagensvej 135, 4, DK-2200 Copenhagen N, Denmark
Keywords: muskox, census techniques, Ovibos, Greenland

Abstract

While conductioning muskox-censuses (Ovibos moschatus) in winter in Jameson Land, NE Greenland, from a fixed-wing aircraft, we examined the width of transects covered. We used a laser range-finder binocular for measuring the distance to observed groups. We found that 1000 m was a reasonable limit for observing a high proportion of the muskoxen present even though it was possible to observe muskoxen from 4000 m or even more. Using two observers on the right side of the aircraft each speaking into a tape recorder with an automatic time signal, we recorded observations and performed a double-observer experiment. By matching the group sizes and perpendicular distances with times of observation we could compare observations of the two observers. We found that both observers missed up to 25% of muskoxen within a 2000 m transect width. The main reasons for missing animals is difficulty in obtaining reference points in snow covered landscape and fatigue of the observers. Calibration of estimated distances using read-outs from the laser-range finder is an adequate method of obtaining distance data for line transect calculations. Our double-observer experiment demonstrated that even groups close to the transect are easily missed.
Published
1993-12-01
How to Cite
AastrupP., & MosbechA. (1993). Transect width and missed observations in counting muskoxen (Ovibos moschatus) from fixed-wing aircraft. Rangifer, 13(2), 99-104. https://doi.org/10.7557/2.13.2.1096
Section
Articles