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Detection Probability and Sources of Variation in White‐Tailed Deer Spotlight Surveys
Author(s) -
COLLIER BRET A.,
DITCHKOFF STEPHEN S.,
RAGLIN JOSHUA B.,
SMITH JORDAN M.
Publication year - 2007
Publication title -
the journal of wildlife management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.94
H-Index - 111
eISSN - 1937-2817
pISSN - 0022-541X
DOI - 10.2193/2005-728
Subject(s) - odocoileus , transect , distance sampling , statistics , sampling (signal processing) , population , population size , statistical power , abundance estimation , abundance (ecology) , geography , ecology , biology , mathematics , computer science , demography , filter (signal processing) , sociology , computer vision
As a first step in understanding structure and dynamics of white‐tailed deer ( Odocoileus virginianus ) populations, managers require knowledge of population size. Spotlight counts are widely used to index deer abundance; however, detection probabilities using spotlights have not been formally estimated. Using a closed mark—recapture design, we explored the efficiency of spotlights for detecting deer by operating thermal imagers and spotlights simultaneously. Spotlights detected only 50.6% of the deer detected by thermal imagers. Relative to the thermal imager, spotlights failed to detect 44.2% of deer groups (≥1 deer). Detection probabilities for spotlight observers varied between and within observers, ranging from 0.30 (SE = 0.053) to 0.66 (SE = 0.058). Managers commonly assume that although road counts based on convenience sampling designs are imperfect, observers can gather population‐trend information from repeated counts along the same survey route. Our results indicate detection rate varied between and within observers and surveyed transects. If detection probabilities are substantially affected by many variables, and if transect selection is not based on appropriate sampling designs, it may be impractical to correct road spotlight counts for detection probabilities to garner unbiased estimates of population size.