Comparisons of Lethal and Nonlethal Techniques to Reduce Raccoon Depredation of Sea Turtle Nests

Ratnaswamy, Mary J.; Warren, Robert J.; Kramer, Monique T.; Adam, Michael D.

doi:10.2307/3802593

Cited by 59 publications

(42 citation statements)

References 9 publications

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“…Protective cages constructed of galvanized wire are commonly placed around sea turtles nests to protect them from predators [45,46]. At least some of these cages significantly alter the magnetic field around the incubating clutch [16].…”

Section: Discussionmentioning

confidence: 99%

The geomagnetic environment in which sea turtle eggs incubate affects subsequent magnetic navigation behaviour of hatchlings

et al. 2014

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Loggerhead sea turtle hatchlings (Caretta caretta) use regional magnetic fields as open-ocean navigational markers during trans-oceanic migrations. Little is known, however, about the ontogeny of this behaviour. As a first step towards investigating whether the magnetic environment in which hatchlings develop affects subsequent magnetic orientation behaviour, eggs deposited by nesting female loggerheads were permitted to develop in situ either in the natural ambient magnetic field or in a magnetic field distorted by magnets placed around the nest. In orientation experiments, hatchlings that developed in the normal ambient field oriented approximately south when exposed to a field that exists near the northern coast of Portugal, a direction consistent with their migratory route in the northeastern Atlantic. By contrast, hatchlings that developed in a distorted magnetic field had orientation indistinguishable from random when tested in the same north Portugal field. No differences existed between the two groups in orientation assays involving responses to orbital movements of waves or sea-finding, neither of which involves magnetic field perception. These findings, to our knowledge, demonstrate for the first time that the magnetic environment present during early development can influence the magnetic orientation behaviour of a neonatal migratory animal.

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Section: Discussionmentioning

confidence: 99%

The geomagnetic environment in which sea turtle eggs incubate affects subsequent magnetic navigation behaviour of hatchlings

et al. 2014

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“…Coblentz & Coblentz, 1985;Engeman et al, 2002), or protecting individual nests, either by applying protective devices to nests in situ (e.g. Ratnaswamy et al, 1997;Yerli et al, 1997) or by relocating the entire clutch to low-risk areas . Predator removal often has only a short-term effect (Engeman et al, 2006) and its impact could be optimized by synchronizing removal efforts with periods of highest predation risk.…”

Section: From Risk Models To Conservationmentioning

confidence: 99%

“…Fowler, 1979;Nellis & Small, 1983;Macdonald et al, 1994), with a strong geographic and taxonomic bias toward predation by native raccoons on loggerhead sea turtles along the south-east coast of the USA (e.g. Ratnaswamy et al, 1997;Engeman et al, 2006;Barton & Roth, 2008). The goals of this research were to develop a predictive model of predation risk for sea turtle nests threatened by an introduced predator of widespread importance in the Caribbean and, more generally, to explore the potential of survival analysis to provide unique and practical insights for predation management in sea turtle nesting areas.…”

Section: Introductionmentioning

confidence: 99%

Predicting nest survival in sea turtles: when and where are eggs most vulnerable to predation?

Leighton

Horrocks

Kramer

2010

Animal Conservation

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Nest predation is an important practical challenge for the conservation of egglaying reptiles, with the potential to reduce hatchling recruitment and slow the recovery of threatened populations. Accurately forecasting where and when predation will occur has the potential to optimize predation management. Survival analysis, a set of statistical techniques recently popularized in studies of avian nest success, provides a unique approach for modelling variation in egg mortality risk throughout development. We used Cox proportional hazards regression to model the survival of sea turtle eggs from predation by the small Asian mongoose Herpestes javanicus, a widely introduced and destructive sea turtle nest predator in the Caribbean. We evaluated the ability of models to predict egg survival using 7 years of nest predation data for critically endangered hawksbill sea turtles Eretmochelys imbracata in Barbados. Daily predation risk was the highest for freshly laid nests, decreasing rapidly with nest age but increasing again near the end of development. Predation risk was the highest in and near patches of beach vegetation, increased over the nesting season and increased with nest density on the open beach but not in vegetation. Survival models calibrated using data from 2004 to 2005 showed excellent discrimination and Z84% accuracy when predicting the fate of nests from previous years. Our study provides the first quantification of the daily variation in predation risk for incubating turtle eggs, revealing a narrow time window early in development during which the application of predation reduction measures is likely to have the greatest impact on nest survival. More generally, we demonstrate the utility of survival analysis for generating finescale predictions of spatiotemporal variation in turtle egg mortality, providing a flexible tool for the conservation of sea turtles and other egg-laying reptiles.

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“…However, population control is not always feasible and is prohibited by wildlife legislation in some areas. Modification of nests to deter predators or to alter the cues predators use to locate them provides a potential alternative method for reducing nest predation (Ratnaswamy et al 1997;Longo et al 2009). Understanding the cues that predators use to find nests and modifying these cues to reduce nests' detectability could facilitate the recovery of species threatened by nest predation.…”

Section: Introductionmentioning

confidence: 98%

Investigation of cues used by predators to detect Snapping Turtle (Chelydraserpentina) nests

Oddie

Coombes²,

Davy

2015

Can. J. Zool.

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Nest predation is the leading cause of reproductive mortality in oviparous tetrapods and can limit population growth in some species. Rates of nest predation could be influenced through modification of the cues used to find nests, but this requires a clear understanding of how nests are located. Here, we used a buffet-style choice experiment to test the relative role of three cue types (visual, tactile, and chemosensory) on the detection and depredation of Snapping Turtle (Chelydra serpentina (L., 1758)) nests by a suite of predators dominated by raccoons (Procyon lotor (L., 1758)). We created sets of artificial nests along an authentic nesting site, presenting single or multiple cues. We interspersed artificial nests with authentic nests and monitored predation rates on both. Predators used all three cues to locate potential nests for investigation. However, nests with tactile cues were significantly more likely to be depredated than nests with only visual and chemosensory cues. Multiple cues had additive effects on predation probability. Addition of chemosensory cues to tactile treatments increased the probability of predation. The importance of tactile cues in this system supports the use of nest cages to protect nests in early stages of development, but cannot explain the recently described late-stage peak in predation.Résumé : La prédation sur les nids, première cause de mortalité associée à la reproduction chez les tétrapodes ovipares, peut limiter la croissance de la population de certaines espèces. Les taux de prédation sur les nids pourraient être influencés par la modification des signaux utilisés pour trouver les nids, mais cela nécessite une bonne compréhension des moyens employés pour localiser des nids. Nous avons utilisé une expérience de sélection de type buffet pour vérifier les rôles respectifs de trois types de signaux (visuels, tactiles et chimiosensoriels) dans la détection et la déprédation de nids de chélydre serpentine (Chelydra serpentina (L., 1758)) par un ensemble de prédateurs dominé par les ratons laveurs (Procyon lotor (L., 1758)). Nous avons créé des séries de nids artificiels dans un site de nidification authentique, ces nids présentant un ou plusieurs signaux. Nous avons intercalé des nids artificiels parmi des nids authentiques et surveillé les taux de prédation sur les deux types de nids. Les prédateurs utilisaient les trois signaux pour localiser des nids potentiels à examiner. Les nids présentant des signaux tactiles étaient toutefois significativement plus susceptibles d'être la cible de déprédation que les nids ne présentant que des signaux visuels et chimiosensoriels. Les effets de signaux multiples sur la probabilité de prédation étaient cumulatifs. L'ajout de signaux chimiosensoriels à des traitements tactiles se traduisait par une probabilité de prédation accrue. L'importance des signaux tactiles dans ce système appuie l'utilisation de cages pour protéger les nids durant les premières étapes du développement, mais ne peut expliquer la pointe de prédation décrite récemmen...

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Comparisons of Lethal and Nonlethal Techniques to Reduce Raccoon Depredation of Sea Turtle Nests

Cited by 59 publications

References 9 publications

The geomagnetic environment in which sea turtle eggs incubate affects subsequent magnetic navigation behaviour of hatchlings

The geomagnetic environment in which sea turtle eggs incubate affects subsequent magnetic navigation behaviour of hatchlings

Predicting nest survival in sea turtles: when and where are eggs most vulnerable to predation?

Investigation of cues used by predators to detect Snapping Turtle (Chelydraserpentina) nests

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