Behavioral Ecology Advance Access originally published online on October 21, 2009
Behavioral Ecology 2009 20(6):1299-1306; doi:10.1093/beheco/arp139
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How depth alters detection and capture of buried prey: exploitation of sea turtle eggs by mongooses
a Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montreal H3A 1B1, Canada b Department of Biological and Chemical Sciences, University of the West Indies, Barbados, West Indies
Address correspondence to P.A. Leighton. E-mail: patrick.leighton{at}mail.mcgill.ca.
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Abstract |
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Predators are an important source of mortality for animals that lay their eggs in buried nests. We asked how depth alters the process of predation for buried prey. We outlined a general model of predation risk where depth may alter both prey detection and subsequent capture: deeper prey are detected less often because the strength of olfactory cues decreases with burial depth and, once detected, are further protected by the costs of digging. Using this framework, we examined how burial depth influenced egg predation for critically endangered hawksbill sea turtles (Eretmochelys imbricata) by introduced mongooses (Herpestes javanicus) in Barbados. We tested the effects of nest depth on detection and subsequent predation using observational data on hawksbill nests over a 2-year period and an experiment with artificial nests. For both real and artificial nests, depth had little effect on nest detection by mongooses, but once detected, shallower nests were much more likely to be preyed on. Mongooses appear to use depth-invariant surface cues to detect nests but increase digging persistence in response to olfactory cues. We argue that excavation cost is an important but overlooked mechanism protecting deeply buried resources. For reptiles with buried nests, the relationship between depth and predation risk leads to important predictions about how changes to nesting habitat or the predator community will affect egg survival and offspring sex ratio. More generally, identifying the mechanisms by which burial depth protects prey is essential for understanding how resource burial strategies evolved and are maintained in predator–prey systems.
Key words: cache recovery, conservation, hatching success, Herpestes auropunctatus javanicus, invasive species, temperature-dependent sex determination.
Received 19 February 2009; revised 20 July 2009; accepted 25 August 2009.