Implications of intraguild predation for sea turtle nest protection

    Authors

    B. T. Barton;J. D. Roth

    Comments

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    Abbreviated Journal Title

    Biol. Conserv.

    Keywords

    Caretta caretta; ghost crab; loggerhead; nest predation; Ocypode; quadrata; predator removal; Procyon lotor; raccoon; GHOST CRAB; OCYPODE-QUADRATA; RACCOON REMOVAL; SANDY BEACHES; MARINE; COMPETITION; MANAGEMENT; DYNAMICS; ECOLOGY; FLORIDA; Biodiversity Conservation; Ecology; Environmental Sciences

    Abstract

    In the United States, raccoons Procyon lotor are often removed from sea turtle nesting beaches to decrease egg mortality. However, raccoons also consume ghost crabs Ocypode quadrata, another common egg predator. Reducing predator populations can benefit secondary predators, inflating total predation pressure and leading to a decline in prey species. We used track and burrow counts to compare raccoon and ghost crab abundance at four beaches in Florida, USA, that differ in management activity and determined predation rates on loggerhead Caretta caretta nests by each predator. Mean raccoon abundance (range 0.12-0.46 tracks plot(-1) night (1)) and ghost crab density (0.09-0.19 burrows m(-2)) were inversely correlated. Ghost crabs were largest at the site with the fewest raccoons. The stable nitrogen isotope ratios of ghost crabs (mean 9.8 parts per thousand) were positively correlated with body mass, indicating larger ghost crabs feed at a higher trophic level and suggesting large ghost crabs may consume more loggerhead eggs. The highest rates of egg predation by both predators (31%) occurred where raccoon abundance was lowest and ghost crab abundance was highest, suggesting ghost crab burrows may facilitate predation by raccoons. Our data suggest that predation by raccoons limits ghost crabs and that removing raccoons can increase ghost crab abundance and sea turtle egg mortality. Although predator removal can be effective when nest predation rates are quite high, maintaining moderate raccoon densities may be important for controlling ghost crabs. These results highlight the importance of understanding food web connectivity in developing management strategies to achieve conservation goals, especially when the species of concern are threatened or facing extinction. (C) 2008 Elsevier Ltd. All rights reserved.

    Journal Title

    Biological Conservation

    Volume

    141

    Issue/Number

    8

    Publication Date

    1-1-2008

    Document Type

    Article

    Language

    English

    First Page

    2139

    Last Page

    2145

    WOS Identifier

    WOS:000259389600020

    ISSN

    0006-3207

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