Estimating density of Florida Key deer
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Florida Key deer (Odocoileus virginianus clavium) were listed as endangered by the U.S. Fish and Wildlife Service (USFWS) in 1967. A variety of survey methods have been used in estimating deer density and/or changes in population trends for this species since 1968; however, a need to evaluate the precision of existing and alternative survey methods (i.e., road counts, mark-recapture, infrared-triggered cameras [ITC]) was desired by USFWS. I evaluated density estimates from unbaited ITCs and road surveys. Road surveys (n = 253) were conducted along a standardized 4-km route each week between January 1999ÂDecember 2000 (total deer observed, n = 4,078). During this same period, 11 ITC stations (1 camera/42 ha) collected 5,511 deer exposures. Study results found a difference (P < 0.001) between methods with road survey estimates lower (76 deer) than ITC estimates (166 deer). Comparing the proportion of marked deer, I observed a higher (P < 0.001) proportion from road surveys (0.266) than from ITC estimates (0.146). 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. I suggest that ITC estimates are a reliable and precise alternative to road surveys for estimating Key deer densities on outer islands. I also evaluated density estimates from 3 road survey methods. Road survey methods (n = 100) were conducted along a standardized 31-km route where markresight, strip-transect, and distance sampling data were collected between June 2003Â May 2004. I found mark-resight estimates to be lower ( x = 384, 95% CI = 346Â421) than strip-transect estimates ( x = 854, 95% CI = 806Â902) and distance estimates ( x = 523, 95% CI = 488Â557). I attribute low mark-resight estimates to urban deer behavior resulting in a higher proportion of marked deer observations along roadways. High strip-transect estimates also are attributed to urban deer behavior and a reduced effective strip width due to dense vegetation. I propose that estimates using distance sampling eliminate some of these biases, and recommend their use in the future.
Roberts, Clay Walton (2005). Estimating density of Florida Key deer. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from