Damien Chevallier

Dispersal and Diving Adjustments of the Green Turtle Chelonia mydas in Response to Dynamic Environmental Conditions during Post-Nesting Migration

In response to seasonality and spatial segregation of resources, sea turtles undertake long journeys between their nesting sites and foraging grounds. While satellite tracking has made it possible to outline their migration routes, we still have little knowledge of how they select their foraging grounds and adapt their migration to dynamic environmental conditions. Here, we analyzed the trajectories and diving behavior of 19 adult green turtles (Chelonia mydas) during their post-nesting migration from French Guiana and Suriname to their foraging grounds off the coast of Brazil. First Passage Time analysis was used to identify foraging areas located off Ceará state of Brazil, where the associated habitat corresponds to favorable conditions for seagrass growth, i.e. clear and shallow waters. The dispersal and diving patterns of the turtles revealed several behavioral adaptations to the strong hydrodynamic processes induced by both the North Brazil current and the Amazon River plume. All green turtles migrated south-eastward after the nesting season, confirming that they coped with the strong counter North Brazil current by using a tight corridor close to the shore. The time spent within the Amazon plume also altered the location of their feeding habitats as the longer individuals stayed within the plume, the sooner they initiated foraging. The green turtles performed deeper and shorter dives while crossing the mouth of the Amazon, a strategy which would help turtles avoid the most turbulent upper surface layers of the plume. These adjustments reveal the remarkable plasticity of this green turtle population when reducing energy costs induced by migration.

Beach morphological changes in response to marine turtles nesting: a preliminary study of Awala-Yalimapo beach, French Guiana (South America)

ABSTRACT Péron, C. , Chevallier, D., Martin G., Chatelet A., Anthony, E.J., Le Maho Y., Gardel, A., 2013. Beach morphological changes in response to marine turtles nesting: a preliminary study of Awala-Yalimapo beach, French Guiana (South America) Each year from February through July, Chelonia mydas (green turtles) and Dermochelys coriacea (leatherback turtles) come to nest on Awala-Yalimapo beach. During the nesting season, the presence of gravid turtles may directly affect the general morphology of the beach by provoking sand remobilization during firstly the conception of their nest and then during the nest disguising. Digital elevation models were realized to qualify and quantify the topographic modification conducted by the macro-bioturbation effect of marine turtles. Green turtles and leatherback turtles do not provoke the same perturbation on the beach. C. mydas affect the upper part of the beach by constructing their nest. Whereas D.coriacea provoke more important impact on the lower upper-beach when they come to lay. During the covering activity leatherback tend to disturb the morphology of the beach around their nests. Morphological changes on the beach during the nesting season draw attention to the potential effect of animal on their terrestrial habitat.

Importance of the connectivity of Spanish stopovers for Black Storks

Capsule Sixteen Black Storks (Ciconia nigra) were tracked by satellite during their autumnal and spring migrations in order to identify their major stopover sites and connections between stopovers in Europe and Africa. Among journeys with stopovers, the longest distance that a stork travelled without stopover was 2433 km (defined here as ‘accessible distance’) meaning that those storks which have stopovers use only a single stopover on average, and this is usually in Spain. We identified nine crucial stopovers (seven in Spain and two in Africa) with high connectivity highlighting the importance of Spanish stopover locations on the flyway of Black Storks.

New epizoic diatom (Bacillariophyta) species from sea turtles in the Eastern Caribbean and South Pacific

Obligately epizoic diatoms (Bacillariophyta) on vertebrates were first described from cetaceans, but turtles, both freshwater and marine, also host very specific floras. Several scrapings of juvenile Chelonia mydas have allowed the description of two new diatom taxa whose valves are asymmetrical about the transapical axis, Tripterion societatis sp. nov. and Chelonicola caribeana sp. nov. These taxa are very small and show some morphological plasticity. Such plasticity might suggest their inclusion in genera with slightly different characteristics from Tripterion and Chelonicola as originally delimited. Based on our observations, an emended diagnosis is proposed for Chelonicola.

First evaluation of the cookie-cutter sharks (Isistius sp.) predation pattern on different cetacean species in Martinique

Cookie-cutter sharks (Isistius sp.) are small squaloid sharks that live in tropical and sub-tropical oceans. Their name comes from their unique tactic of feeding, which enables them to parasitize marine mega-fauna, like cetaceans. Due to their morphological and anatomical characteristics, they are responsible of crater-like wounds on the skin of marine mammals. Little is known on Isistius sp. around the globe especially in Martinique, which represents a potential habitat. The main goal of this study was to assess the impact of cookie-cutter sharks on cetaceans by determining (1) seasonal changes in the occurrence of bites, (2) intra- and interspecific differences in frequencies and locations of bites among the different species of cetaceans, and (3) link behavior patterns of both cookie-cutter sharks and cetaceans. Data were collected from a 3-year photo-identification database of Cetaceans in Caribbean coast of Martinique. 431 wounds of various stages on 396 individuals from nine species of marine mammals were recorded. Results did not show any significant variation in the occurrence of wounds between seasons. Intermediate state was more important, most injuries were observed on the SCF (Superior Central Flank) (62.40%) and in a lesser extent on young individuals (3.25%). The predation of cookie-cutter sharks on different cetacean species has been confirmed consistently in Martinique. Further studies are required with both scientists and fishermen to better understand their specific role in this marine ecosystem.