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Melanosuchus niger (Crocodylia: Alligatoridae) as opportunistic turtle consumer in its natural environment
Abstract and Figures
En el presente trabajo se hicieron observación de depredadores potenciales de quelonios existentes en el medio río Negro, municipio de Barcelos, Amazonas, Brasil. Se trabajó en dos localidades del municipio de Barcelos: Igarapé del río Negro Lodge y Arirá. Para la captura científica de los quelonios se utilizaron mallas y trampas de red, en las cuales además se atrapaban peces y algunos caimanes negros que entraban para comer y que eran registrados visualmente y por la evidencia de daño causado en las tortugas. En general los Crocodylia incluyen en su dieta quelonios, siendo Melanosuchus niger (caimán negro) registrado por primera vez para esta área de trabajo como depredador de tortugas: Podocnemis erythrocephala (irapuca) y en especial de Peltocephalus dumerilianus (cabezudo). La relación existente entre depredador y presa en este caso muestra poca documentación, a pesar de existir una amplia variedad de estudios relacionados.
... This is in contrast to what was described by [29], who performed studies in captive turtles. The absence of animals with clinical signs in a sample of free-living specimens may be justified by the effect of natural predation as reported by [30] on Panthera onca and P. expansa and also described by [31] on Melanosuchus niger and P. expansa, as weakened animals are more susceptible to these predation events compared to unparasitized animals. ...
Methods: Sampling was performed at three sites in the Tapajós River mouth, Pará State, Brazil, and an aliquot of blood was collected from each turtle by post-occipital dorsal vein puncture. The aliquots were used for the determination of hemato-logical parameters and for the study of hemoparasites in the blood samples.
Results: A total of 37 turtles were sampled: 21 Podocnemis expansa, three P. sextuberculata, nine P. unifilis, and four P. erythrocephala. Parasitological analyses showed inclusions in erythrocytes compatible with Haemogregarina sp., representing an overall prevalence of parasitized animals of 64.8% with an average of 94,789 parasites/ml of blood. In this study, the evolutionary forms of Haemogregarina spp. from trophozoites, pre-meronts, meronts, and mature and immature gamonts were observed in three species of freshwater turtle species, and one morphotype of the parasite with high similarity to Haemogregarina podocnemis has been observed.
Conclusion: Despite recent research on freshwater turtles, this study provides new information on the intensity of blood parasite infection and hematological parameters of free-living animals, highlighting the need for studies on infected and uninfected animals from the same population.
... eat comes from De La Ossa et al. (2010), who observed two adult individuals enter turtle traps and eat the turtles inside. Given that the prey was in captivity when they were eaten, it remains unclear what adult black caiman choose to eat under natural conditions. ...
The black caiman (Melanosuchus niger) is one of the largest predators in South America, yet we know little about adult diets. We studied stomach contents of adults in Guyana and found the largest individuals target mammals instead of fish and males exhibit cannibalism, a behavior never recorded for this species previously. The black caiman (Melanosuchus niger) is one of the largest predators in South America, yet we know little about adult diets. We studied stomach contents of adults in Guyana and found the largest individuals target mammals instead of fish and males exhibit cannibalism, a behavior never recorded for this species previously.
... O jacaré-açu (Melanosuchus niger) é o maior predador do bioma Amazônia e ocorre em simpatria com as maiores espécies sul-americanas de quelônios dulcícolas (Ross & Magnusson, 1989;Vogt, 2008). O ataque oportunista desse crocodiliano Alligatoridae sobre quelônios Podocnemididae capturados em equipamento de pesquisa (fyke net, trammel net) já foi observado para Peltocephalus dumerilianus e Podocnemis erythrocephala (De la Ossa et al., 2010). Esses autores também relataram a predação desse crocodiliano sobre Podocnemis expansa e Podocnemis sextuberculata durante a aglomeração anual de nidificação. ...
461 Primeiro relato de desovas múltiplas de tracajá (Podocnemis unifilis) em ninho de jacaré-açu (Melanosuchus niger) na Amazônia First record of multiple nests of yellow-spotted river turtle (Podocnemis unifilis) in a nest of black caiman (Melanosuchus niger) in Amazonia Resumo: A presente comunicação relata o primeiro registro de desova conjunta de fêmeas de tracajá (Podocnemis unifilis) em um ninho de jacaré-açu (Melanosuchus niger) em área de savana alagada no município de Oiapoque, norte do estado do Amapá, Amazônia brasileira. No interior do ninho do M. niger encontramos 182 ovos de P. unifilis, divididos em oito posturas. Abstract: This communication reports the first record of communal egg-laying of yellow-spotted river turtle (Podocnemis unifilis) in a nest of the black caiman (Melanosuchus niger). This event was recorded in a flooded savannah in the municipality of Oiapoque, northern Amapá state, Brazilian Amazonia. Inside the nest of M. niger we founded 182 eggs of P. unifilis divided into eight clutches.
Se reporta la crianza en cautiverio de neonatos de Melanosuchus niger, a partir de la incubación de huevos de tres nidos recolectados de áreas naturales por el sistema de rancheo. Sobrevivieron 06 neonatos que fueron colocados en una pecera de vidrio de 1.40, 0.40 x 0.50 m3, durante nueve meses. Un neonato murió por ataque de roedores y dos por prematuridad. Luego fueron trasladados por tres meses en un ambiente semi – natural, de 8 x 12 m2, donde compartieron espacio y alimentación con las otras tres especies de caimanes amazónicos, todos juveniles. La alimentación fue a base de peces. Los neonatos, al momento de la eclosión, tuvieron una longitud total de 29.93 cm = 299.3 mm (29.6 a 30.8 cm), y un peso de 86.67g (82 a 93 g). En doce meses tuvieron un crecimiento promedio en longitud total de 46.22 cm = 462.2 mm y peso de 286.14 g. El crecimiento mensual de la longitud total tuvo una ganancia promedio de 3.01 cm = 30.1 mm, con crecimiento diario de 0.12cm = 1.2 mm; y el incremento mensual de peso de 55 g, con un incremento diario de 1.83 g.
American alligators Alligator
mississippiensis undergo major transformations in morphology and ecology during development. These include several thousand-fold changes in body mass, modified snout and dental proportions, and shifts in diet from small, delicate foodstuffs to the inclusion of increasingly larger, more robust prey. How these changes in anatomical form contribute to actual physical performance and niche use is largely unknown. In the present study, bite-force measurements for 41 specimens of A.
mississipiensis, were made throughout ontogeny (hatchling–older adults) using a series of precision force transducers. How this performance indicator scaled with respect to cranial and whole-body measurements was determined. Bite-force production throughout development was contrasted with ontogenetic changes in trophic ecology. The influences of this performance measure on these changes were then analysed. The results showed a 800-fold range (12–9452 N) of bite forces with values positively correlating with increases in body size. Scaling of biting forces through ontogeny showed positive allometry with respect to body mass, head length, jaw length, snout–vent length and total length. These patterns may be attributable to allometric growth of individual skeletal elements (and associated musculature), and/or progressive fusion and ossification of skull and jawbones during development. The overall pattern of force increase throughout ontogeny did not vary in association with major shifts in diet. Notably, the bite-force values for adult A.
mississippiensis are the highest measured for any living animal and represent the first measures for a large crocodilian. Additionally, these data provide the first documentation of how bite force changes during ontogeny in a reptile. By bridging the rich morphological and ecological databases for these animals, this study opens the door to a comprehensive understanding of feeding in A.
mississippiensis. Furthermore, it provides groundwork for standardized comparative studies of feeding among crocodilian, reptilian, or other gnathostome vertebrates.
The foods of wild juvenile saltwater crocodiles (Crocodylus porosus) are described, and rates of feeding, nutrient intake and growth are quantified. The size of prey eaten is strongly bimodal: large numbers of small prey (mainly crustaceans) and small numbers of large prey (mainly rats). The nutrient intake levels reflect size related changes in diet (more larger prey in larger crocodiles). The average juvenile diet is characterized by 70-71% water, low fat levels (3.0-4.5%), high protein content (12.7-14.7%), and calcium:phosphorus ratios which decline from 7:1 in animals 300-599 mm total length (TL), to 2:1 in animals 900-1200 mm TL. A mean food conversion rate (wet weight to wet weight) of 82.4% is derived, which is appreciably higher than results obtained from captive crocodilians (17-40%). To maintain similar growth rates, a wild juvenile C. porosus of 682 mm TL requires food equivalent to 4% of its body weight per week, whereas captive counterparts require four times that amount. The physiological mechanisms associated with digestion and assimilation may not function as efficiently when the stomach is repeatedly filled to capacity, as occurs in captivity.
Caiman population studies were carried out during the 2001 and 2003 dry seasons at the Abufari Biological Reserve (ABR), situated in lower Purus river, at 450 km Southwest of Manaus, to assess the distribution and abundance of caimans along different habitats. The Purus River is a white-water river, which during wet season is continuous with the floodplain (complex riparian streams and lake habitats). Spotlight surveys for counting caimans covered 33.3 km of the Purus River, and 28.3 km of lakes and tributaries. Of the 1,217 caimans counted, 872 were identified on the species level (76% black caiman, 24% spectacled caiman). The relative abundance of caimans observed in 2001 was higher than in 2003, but this difference was not significant. One third of the caimans observed were above minimum reproductive size. The caiman distribution based on distribution and abundance is described by three clusters that correspond to habitats where there is high biomass (M. niger), intermediate biomass (M. niger and C. crocodilus), and low biomass (C. crocodiles). Human-caiman interactions measured by the disturbance index were higher on the main river and in the neighborhood of settlements than in stream channels, beaches and remote areas. However, the caiman populations in the lower Purus River were notable in that black caiman abundance was higher when compared with other Amazon studies. Further studies on caiman population are necessary to evaluate the sex ratio and mainly the reproductive sites of these species. It is also important to insert the local community in conservation research programs of caimans in such a way as to promote sustainable use. No presente estudo foram avaliadas a densidade, estrutura populacional e utilização de habitats por Melanosuchus niger e Caiman crocodilus na Reserva Biológica do Abufari, situada no baixo rio Purus. O estudo foi realizado em setembro de 2001 e 2003. Foram observados 1217 jacarés, M. niger e C. crocodilus representam 76% e 24%, respectivamente, do total de animais observados. Durante o estudo foram percorridos 33,3 km de margens do rio Purus e 28,3 km de margens em lagos e tributários. Densidade total de jacarés observada em 2001 (24 jacares/km) foi maior que a 2003 (17 jacarés/km), mas a diferença não foi significativa estatisticamente. Os dados preliminares mostram uma população composta por indivíduos de porte elevado. Muitos M. niger e C. crocodilus observados estavam acima do tamanho mínimo reprodutivo 30,85% e 27,73%, respectivamente. As distribuições de crocodilianos nos diferentes ambientes foram avaliadas a partir de dados de distribuição e abundância que mostraram a existência de três agrupamentos, sendo um deles ocupado predominantemente por jacaré-açú (M. niger), outro por duas espécies, o jacaré-tinga (C. crocodilus) e jacaré-açú e um terceiro agrupamento onde predominava o jacaré-tinga. A interação homem-crocodiliano foi medida pelo índice de distúrbio, o qual foi maior nos rios e áreas próximas das comunidades ribeirinhas do que nos canais de igarapés, praias e áreas remotas. Estudos posteriores são necessários para avaliar de forma mais precisa a estrutura populacional, razão sexual e identificar os habitats importantes para a reprodução destas espécies no baixo rio Purus. Além disso, é importante inserir as comunidades ribeirinhas no processo de pesquisa, conservação e uso sustentável do recurso. En el presente estudio fueran investigadas la densidad, tallas de la población y la utilización de los ambientes por Melanosuchus niger y Caiman crocodilus en la Reserva Biológica de Abufari, situada en el bajo río Purus. El estudio fue desarrollado en septiembre de los años 2001 y 2003. Fueran observados 1.217 caimanes, donde M. niger y C. crocodilus corresponden al 76% y al 24%, respectivamente. Durante el estudio fueran investigados 33,3 km de margen del rio Purus y 28,3 km de margen en los lagos e tributarios. La abundancia relativa de caimanes observada en el año 2001 (24 caimanes /km) fueran mucho mayores que las del año 2003 (17 caimanes/km), pero las diferencias no fueran estadísticamente significativas. Los datos muestran que tanto la población de caimán negro como la populación de los babas están compuestas por individuos de tallas grandes. Muchos M. niger y C. crocodilus observados estaban por encima de la menor talla reproductiva 30,85% y 27,73%, respectivamente. Las distribuciones de caimanes en los ambientes fueran basadas en dados de distribución y abundancia que mostraron tres agrupamientos, siendo uno de estos predominantemente ocupado por caimán negro (M. niger), otro tanto por caimán negro como por baba (C. crocodilus) e un tercero donde predominaban el baba (C. crocodilus). La interacción hombre-caimán medida por el índice de disturbación, que fue mayor en los ríos y áreas próximas a las comunidades ribereñas do que nos canales de pequeños riachos, playas y áreas remotas. Investigaciones posteriores son necesarias, porque permitirán de una forma más precisa una mejor evaluación de las proporciones sexuales y permitirán también identificar los ambientes importantes para la reproducción de estas dos especies de caimanes. Además, es importante incluir las comunidades ribereñas en el proceso de investigación, conservación y uso sostenible del recurso.
During 1992 and 1994, 88 individuals of black caiman (Melartostschus niger) were captured in an oxbow lake in Mann National Park, Peruvian Amazonia. Stomach contents were collected without killing the animals. Fifteen prey categories including invertebrates and vertebrates were found in the stomachs. Snails (Pomatia spp.) and fish were the main items present in the diet. Snails were more abundant in the diet of juveniles and fish more abundant in that of adults. Frogs, birds, and mammals were also eaten. Results from both descriptive statistics and multivariare ordination analyses indicated that there was a significant effect of ontogeny on diet composition. There were also significant seasonal differences in diet composition, suggesting that in order to resist periods of food scarcity black caimans may adjust their feeding behavior according to changes in prey abundance and occurrence. Although black caimans are top predators, even adults apparently depend on both invertebrates and vertebrates to satisfy their energetic needs. Conservation of this heavily hunted species has to consider protection of natural areas such as lakes and rivers, principally those where a high diversity and abundance of organisms from various trophic levels occurs. Accepted 29 December 2000.
Stomach contents were collected from 213 Caiman crocodilus with snout-vent lengths (SVL) between 15 cm and 115 cm, and 25 Melanosuchus niger with SVLs from 15 cm to 95 cm, in the Anavilhanas Archipelago, Rio Negro, Central Amazonia. The prey types consumed by the two species were generally similar. However, fish were common in the diet of C. crocodilus but absent from the M. niger. Snails (Pomacea) occurred in 24% of stomachs of M. niger, but in only 2% of C. crocodilus. The mean mass of food and the mean proportion of fish consumed increased, while the mean proportion of terrestrial invertebrates decreased significantly with the size class of C. crocodilus. The mean proportion of molluscs consumed increased significantly with the size class of M. niger, but there was no relationship between the mean mass of food or the mean proportion of other prey categories and size class in this species. However, the sample included only subadults. The mean size of all prey consumed, and of fish, increased significantly with size of C. crocodilus. However, there was no relationship between the mean size of prey in the categories terrestrial invertebrates, shrimps, or crabs, and the size of C. crocodilus. The mean size of all prey consumed was positively related to the size of M. niger. The mean mass of food consumed by C. crocodilus varied with the water body type (lake or canal), but there was no effect of season as indexed by the water level of the Rio Negro. Seasonal variation in the proportion of fish, terrestrial invertebrates, and shrimps consumed by C. crocodilus differed among water body types. Empty stomachs occurred in 24% of the C. crocodilus and 20% of the M. niger. Individuals with food in the stomach had eaten small volumes, suggesting that the caiman are unlikely to impact fisheries in the region.
The fall-winter food habits of the Texas river cooter (Pseudemys texana) were investigated at Spring Lake, Hays County, Texas, by examination of stomach contents. Samples were collected from 33 live turtles by flushing stomach contents with water (Fields et al., 2000). Four aquatic macrophytes composed 91.6% of the diet. Aquatic macrophyte availability at Spring Lake was estimated using the Daubenmire technique (Daubenmire and Daubenmire, 1968) and compared to occurrence in the diet to assess selectivity in foraging. Cooters actively selected Carolina fanwort (Cabomba caroliniana), a plant low in fiber and high in total digestible nutrients. Hydrilla (Hydrilla verticilata), an invasive exotic aquatic plant, was an important food item due to the large amount present in the lake.
Crocodilians are able to consume larger meals than most vertebrates. The varied diet of many crocodilians makes them excellent models to study the effects of meal size and temperature on gastric retention time. Consumption of turtles by American alligators, Alligator mississippiensis, is expected to be overemphasized because of prolonged stomach retention of epidermal scutes. We conducted experiments to identify exogenous factors that control gastric retention time of turtle scutes. Stomach contents of nine juvenile alligators, fed various percentages of their body mass, were used to compare retention intervals of turtle scutes. As meal size increased, the stomach retention interval increased. The retention interval of scutes was not affected by ambient temperatures over the range of 30–35 C.
The dilution effect as an antipredation behaviour is the main theoretical reason for grouping in animals and states that all individuals in a group have an equal risk of being predated if equally spaced from each other and the predator. Stalking predators, however, increase their chance of attack success by preferentially targeting nonvigilant individuals, potentially making relative vigilance rates in a group relatively important in determining predation compared with the dilution effect. Many predators, however, attack opportunistically without stalking, when targeting of nonvigilant individuals may be less likely, so that the dilution effect will then be a relatively more important antipredation reason for grouping. We tested whether an opportunistically hunting predator, the sparrowhawk, Accipiter nisus, preferentially attacked vigilant or feeding prey models presented in pairs. We found that sparrowhawks attacked vigilant and feeding mounts at similar frequencies. Our results suggest that individu
ABSTRACT: Understanding the diet of crocodilians is important because diet affects condition, behavior, growth, and reproduction. By examining the diet of crocodilians, valuable knowledge is gained about predator-prey interactions and prey utilization among habitats. In this study, I examined the diet and condition of adult American alligators (Alligator mississippiensis) in three central Florida lakes, Griffin, Apopka, and Woodruff. Two hundred adult alligators were captured and lavaged from March through October 2001, from April through October 2002, and from April through August 2003. Alligators ate a variety of vertebrate and invertebrate prey, but vertebrates were more abundant and fish dominated alligator diets in the lakes. Species composition of fish varied among the lakes. The majority of the diet of alligators from Lakes Apopka and Woodruff was fish, 90% and 84% respectively. ABSTRACT: Lake Apopka alligators consumed a significantly (P=0.006) higher proportion of fish in their diet. Fish were 54% of the diet of Lake Griffin alligators and the infrequent occurrence of reptiles, mammals, birds, and amphibians often resulted in a large biomass. Differences in alligator diets among lakes may be due to differences in sample size (higher numbers of samples from Lake Griffin), prey availability, habitat, prey vulnerability, or prey size. Alligator condition (Fulton's Condition Factor, K) was significantly (P<0.001) different among the lakes. Alligators from Lake Apopka had the highest condition, followed by those from Lake Griffin, and alligators from Lake Woodruff had the lowest condition. Composition of fish along with diversity and equitability of fish in alligator diets may have contributed to differences in condition among lakes. ABSTRACT: Condition was probably also due to factors other than diet such as alligator hunting behavior, alligator density, or year-round optimal temperature that prolongs feeding. The observed diet and condition differences probably reflect both habitat differences and prey availability in these three lakes. Text (Electronic thesis) in PDF format. System requirements: World Wide Web browser and PDF reader. Mode of access: World Wide Web. Title from title page of source document. Document formatted into pages; contains 100 pages. Thesis (M.S.)--University of Florida, 2004. Includes vita. Includes bibliographical references.
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