EVALUATION OF AERIAL LINE TRANSECT METHODOLOGY FOR ESTIMATING RED DEER (CERVUS-ELAPHUS) ABUNDANCE IN SCOTLAND

Aerial line transect methods have been successfully used to count anim als in open country; we describe their application for assessing red d eer (Cervus elaphus) numbers in Scotland. The results of a pilot study in the north of Scotland are compared to a census count carried out i n the same area in the previous year. The aerial line transect method gave an estimate of 2240 red deer in May 1995. This agreed well with t he census count giving 2270 in April 1994. The line transect estimate had a coefficient of variation of 25%, whereas no measure of precision is available for the census count. Separate estimates for the number of stags and the number of hinds and calves were obtained with both me thods. We suggest improvements in the practical application of the aer ial line transect method to increase precision of the abundance estima tes. Aerial line transect surveys require fewer person-days of effort than census counts, and are appreciably more cost effective for assess ing deer numbers over a large area. We present three case studies for applying aerial line transect methods in Scotland. The case studies co mpare the cost and effort for an aerial line transect estimate with th ose of a conventional ground-based census count in West Sutherland and North Ross (Red Deer Commission's counting blocks). Obtaining an esti mate of red deer numbers in North Ross with a coefficient of variation of 10% would take 33% of the time of a census count, require 50% of t he people and take about 60% of the resources required for a ground-ba sed census count. A joint estimate for North Ross and West Sutherland would reduce the time demand for the line transect estimate (10% coeff icient of variation) to about 18% of that required by a census and the resources to 33%. (C) 1997 Academic Press Limited.