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Comparison of Camera and Road Survey Estimates for White‐Tailed Deer
Author(s) -
ROBERTS CLAY W.,
PIERCE BRIAN L.,
BRADEN ANTHONY W.,
LOPEZ ROEL R.,
SILVY NOVA J.,
FRANK PHILIP A.,
RANSOM DEAN
Publication year - 2006
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 - 10.2193/0022-541x(2006)70[263:cocars]2.0.co;2
Subject(s) - odocoileus , wildlife , geography , aerial survey , population , endangered species , distance sampling , forestry , wildlife management , sampling (signal processing) , survey methodology , habitat , environmental science , cartography , ecology , demography , statistics , biology , mathematics , engineering , filter (signal processing) , sociology , electrical engineering
Wildlife managers require reliable, cost‐effective, and accurate methods for conducting population surveys in making wildlife management decisions. Traditional methods such as spotlight counts, drive counts, strip counts (aerial, thermal, infrared) and mark–recapture techniques can be expensive, labor‐intensive, or limited to habitats with high visibility. Convenience sampling designs are often used to circumvent these problems, creating the potential for unknown bias in survey results. Infrared‐triggered cameras (ITCs) are a rapidly developing technology that may provide a viable alternative to wildlife managers because they can be economically used with alternative sampling designs. We evaluated population‐density estimates from unbaited ITCs and road surveys for the endangered Florida Key deer (Odocoileus virginianus clavium) on No Name Key, Florida, USA (461‐ha island). Road surveys (n = 253) were conducted along a standardized 4‐km route each week at sunrise (n = 90), sunset (n = 93), and nighttime (n = 70) between January 1998 and December 2000 (total deer observed = 4,078). During this same period, 11 ITC stations (1 camera/42 ha) collected 8,625 exposures, of which 5,511 registered deer (64% of photographs). Study results found a difference (P < 0.001) between methods with road‐survey population estimates lower (76 deer) than ITC estimates (166 deer). In comparing the proportion of marked deer between the 2 methods, we observed a higher (P < 0.001) proportion from road surveys (0.266) than from ITC estimates (0.146). Spatial analysis of deer observations also revealed the sample area coverage to be incongruent between the 2 methods; approximately 79% of all deer observations were on urban roads comprising 63% of the survey route. Lower road‐survey estimates are attributed to 1) urban deer behavior resulting in a high proportion of marked deer observations, and 2) inadequate sample area coverage. We suggest that ITC estimates may provide an alternative to road surveys for estimating white‐tailed deer densities, and may alleviate sample bias generated by convenience sampling, particularly on small, outer islands where habitat and/or lack of infrastructure (i.e., roads) precludes the use of other methods.