The black caiman is one of the largest neotropical top predators, which means that it could play a structuring role within swamp ecosystems. However, because of the difficulties inherent to studying black caimans, data are sorely lacking on many aspects of their general biology, natural history, and ecology, especially in French Guiana. We conducted a detailed study of the Agami Pond black caiman population using a multidisciplinary approach. The aim was to better understand the species’ dietary ecology and movements in the pond, and thus its functional role in pond system. We gathered natural history data, tracked caiman movements using satellite transmitters, and characterized feeding ecology via stable isotope analysis. Our study was carried out over three sampling periods and spanned both wet and dry seasons, which differ in their hydrological and ecological conditions. Our results show that black caiman abundance and age demographics differed between seasons in Agami Pond. In the dry season, Agami Pond is one of the only areas within the marsh to hold water. It thus contains large quantities of different fish species, which form the basis of the black caiman’s diet. Caiman body size, a proxy for age class, was around 1.5 meters. During the wet season, which corresponds to the breeding period for migratory birds (e.g., Agami herons), adult black caimans are present in Agami Pond. Adults were most abundant in the inundated forest. There, most individuals measured up to 2 meters. They also exhibited a particular “predatory” behavior near bird nests, preying on fallen chicks and adults. Juveniles and subadults were present during both seasons in the pond’s open waters. These behavioral observations were backed up by stable isotope analysis, which revealed ontogenetic variation in the caiman’s isotopic values. This isotopic variation reflected variation in diet that likely reduced intraspecific competition between adults and young. The telemetry and microchip data show that different age classes had different movement patterns and that seasonal variation in the pond may influence caiman prey availability and reproductive behavior. The new information gathered should help predict this species’ responses to potential ecosystem disturbance (e.g., water pollution, habitat destruction) and inform the development of an effective conservation plan that involves locals and wildlife officials.
Après quatre années d’observations préliminaires (1992 à 1995), l’analyse du polymorphisme génétique des caséines du lait des chèvres des Pyrénées a été réalisée en 1996, grâce aux prélèvements de lait et de sang effectués dans 45 élevages, sur un effectif de 410 à 862 chèvres et 63 boucs. L’analyse concerne trois des quatre caséines : αS1, αS2 et β. En caséine αS1, l’allèle moyen E est majoritaire, devant les allèles forts (A, B3 et B4), l’allèle faible F et deux allèles nuls, dont l’allèle O2 bien représenté chez les chèvres et les boucs et dont le centre de diffusion peut être localisé. La caséine αS2 compte trois allèles. La caséine β présente deux allèles, dont un allèle nul observé dans 82 % des élevages à une fréquence de 0,11. Au total, 35 à 45 % des chèvres possèdent un mutant défectif, soit en caséine αS1, soit en caséine β, ce qui n’est pas sans conséquence sur la qualité fromagère des laits. Concernant l’allèle nul en caséine β, la population est en équilibre, mais il existe des différences de fréquence entre les secteurs. A terme, la décision à prendre vis-à-vis des mutants défectifs dépend de l’orientation des éleveurs : production de chevreaux de boucherie dans les troupeaux à viande de type conservatoire ou amélioration de la qualité fromagère des laits dans les élevages laitiers traditionnels.
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