Aerial surveys are an efficient technique for counting animals over large areas. However, only 15– 80% of the population is counted, biasing population estimates low. Distance sampling can be used to account for animals unseen, but only under the assumption that all animals on the transect are observed. Because sightability on the transect is not 100% during surveys, distance sampling conducted in conjunction with a mark-recapture technique, termed “mark-recapture distance sampling,” (MRDS) is an approach that has been used to correct for the undercount on the transect. I flew surveys on 4 study sites in southern Texas to evaluate the feasibility of the MRDS technique. Data were analyzed in Program Distance 6.2. Probability of detection on the survey line for all species ranged from 0.82–0.97 (SE = 0.01–0.07). Probability of detection within the survey area for all species ranged from 0.32–0.64 (SE 0.01–0.06). The MRDS technique addressed imperfect detection on the survey line and provided probabilities of detection in the survey area consistent with previous studies done in Texas. Mark-recapture distance sampling can be used in South Texas to increase accuracy of large mammal aerial surveys, though it may be more economical to use conventional distance sampling.
January 27, 2016
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