U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

August 2003


Published by Biological Conservation 113 (2003)171-178.


The fundamental conservation focus for Hobe Sound National Wildlife Refuge (HSNWR), Florida is to provide protected nesting habitat for three threatened or endangered marine turtle species. Turtle nesting and hatching spans from early spring to fall each year. Left unchecked, nest predation by raccoons and armadillos would destroy most turtle nests. Predators are removed to protect nests, primarily with a one person-month contract using control specialists. We maximized the efficiency of predator removal by using a passive tracking index to: (1)optimize the timing and strategy for predator removal, (2)minimize labor by identifying areas where predator removal would have maximal effects, (3) examine beach invasion patterns of predators, (4) assess efficacy of removal efforts, (5) provide anticipatory information for future turtle nesting seasons, and (6) serve as a detection method for invasion by additional species known to depredate turtle nests. An overall nest predation rate of 28% resulted, where as the rate for the pervious year was 42% when the same level of contracted predator removal was applied, but without monitoring of the nests were destroyed in the years prior to predator removal. Using 2000 data on numbers of nests, clutch sizes, and emergence rates, we estimated the number of hatchings that would have been lost assuming that the predation rates observed from four predator removal scenarios at HSNWR would have occurred in 2000. Historical predation of 95% would have resulted in 120,597 hatchlings lost in 2000. Predator removal as part of regular refuge operations would have reduced this number to 62,481. Addition of a contract with control specialist would have further reduced the number lost to 53,778. Addition of temporal and spatial monitoring for predator removal reduced losses to 36,637.