Year: 2006
Type: dissertation
Abstract: Florida Key deer (Odocoileus virginianus clavium) were listed as endangered by\nthe U.S. Fish and Wildlife Service (USFWS) in 1967. A variety of survey methods have\nbeen used in estimating deer density and/or changes in population trends for this species\nsince 1968; however, a need to evaluate the precision of existing and alternative survey\nmethods (i.e., road counts, mark-recapture, infrared-triggered cameras [ITC]) was\ndesired by USFWS.\nI evaluated density estimates from unbaited ITCs and road surveys. Road\nsurveys (n = 253) were conducted along a standardized 4-km route each week between\nJanuary 1999–December 2000 (total deer observed, n = 4,078). During this same period,\n11 ITC stations (1 camera/42 ha) collected 5,511 deer exposures. Study results found a\ndifference (P < 0.001) between methods with road survey estimates lower (76 deer) than\nITC estimates (166 deer). Comparing the proportion of marked deer, I observed a higher\n(P < 0.001) proportion from road surveys (0.266) than from ITC estimates (0.146).\nLower road survey estimates are attributed to (1) urban deer behavior resulting in a high\nproportion 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\nestimating Key deer densities on outer islands.\nI also evaluated density estimates from 3 road survey methods. Road survey\nmethods (n = 100) were conducted along a standardized 31-km route where markresight,\nstrip-transect, and distance sampling data were collected between June 2003–\nMay 2004. I found mark-resight estimates to be lower ( x = 384, 95% CI = 346–421)\nthan strip-transect estimates ( x = 854, 95% CI = 806–902) and distance estimates ( x =\n523, 95% CI = 488–557). I attribute low mark-resight estimates to urban deer behavior\nresulting in a higher proportion of marked deer observations along roadways. High\nstrip-transect estimates also are attributed to urban deer behavior and a reduced effective\nstrip width due to dense vegetation. I propose that estimates using distance sampling\neliminate some of these biases, and recommend their use in the future.
Author: Clay W. Roberts
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
SDG: Life on land
Open Access status: green
OpenAlex ID: W2289354931