Crocodylus intermedius

Number of Pages: 2Integrative BiologyGeological Science

Population structure, sex ratio and abundance of Podocnemis sextuberculata (Testudines, Podocnemididae) in the Reserva de Desenvolvimento Sustentável Mamirauá, Amazonas, Brazil

Population structure, sex ratio and abundance of Podocnemis sextuberculata (Testudines, Podocnemididae) in the Reserva de Desenvolvimento Sustentável Mamirauá, Amazonas, Brazil. We studied turtles in the focal area of the Reserva de Desenvolvimento Sustentável Mamirauá from September 1996 through August 1998. The reserve is located in the western part of the Brazilian Amazon, between the Japurá, Solimões, and Auti-Paraná rivers, near the city of Tefé, in the state of Amazonas. In this study the populacion structure, sex ratio and abundance of Podocnemis sextuberculata were investigated. We intensively studied the population of turtles in the Jarauá river basin in order to determine population structure. We sampled turtles in different sectors of the focal area of the reserve for one month each year during July and August 1997 and 1998. We captured the turtles using flag gill nets and trammel nets. The type of net and size of the nets used influenced the size of the turtles captured. The nets used by the local fishermen were sexually selective in the capture of turtles. Seventy two per cent of the P. sextuberculata captured were adults; 13 % juveniles and 14.7 % subadults. During the second year of the study we found a lower density of turtles in the five areas which we sampled both years. The sex ratio of captured P. sextuberculata was 1.87 males per female

ORINOCO CROCODILE CROCODYLUS INTERMEDIUS

The Orinoco crocodile is a large, relatively long-nosed crocodile restricted to the middle and lower reaches of the Orinoco River and its tributaries in Venezuela and Colombia Although this crocodile was found in a wide variety of habitats, including rivers in tropical evergreen forest and piedmont streams in the foothills of the Andes, it reached its greatest numbers in the seasonal rivers of the Llanos savanna regio

Conservation and management implications of nest-site selection of the sympatric crocodilians Melanosuchus niger and Caiman crocodilus in Central Amazonia, Brazil

Management of crocodilians is often based on source-sink dynamics, protecting breeding habitat and concentrating hunting in other areas. Nest distributions shed light on habitat use by breeding populations, which might be used as a basis for monitoring and management. The heterogeneous spatial distribution of Melanosuchus niger and Caiman crocodilus in Amazonia has been suggested to reflect past hunting pressure, often underestimating the natural ecological peculiarities of these species. Ground nest surveys combined with satellite imagery allowed us to evaluate whether nest-site use by M. niger and C. crocodilus reflects environmental constraints or is a result of hunting pressure. Our results indicate that there is little evidence that hunting pressure shapes nest-site use of these species in our study areas. M. niger nests mainly on the shores of stable, temporally impounded floodplain lakes isolated from the early stages of the annual rising water of main rivers. This behavior facilitates the identification of suitable nesting sites using moderate-resolution remote-sensing tools and should guide monitoring efforts and the protection of these areas. In contrast, C. crocodilus is a generalist species, able to nest hundreds of meters inside the forest far from permanent water. This makes the occurrence and distribution of nesting-sites unpredictable using Landsat images. Although nests of this species can be found around lakes where nests of M. niger also occur, the protection of these sites might help to preserve only a small portion of C. crocodilus nesting females. Thus, conservation strategies for C. crocodilus should probably be based on different approaches. © 2010 Elsevier Ltd

High levels of population genetic differentiation in the American crocodile (Crocodylus acutus)

The American crocodile (Crocodylus acutus) is a widely distributed species across coastal and brackish areas of the Neotropical region of the Americas and the Greater Antilles. Available information on patterns of genetic differentiation in C. acutus shows a complex structuring influenced by interspecific interactions (mainly hybridization) and anthropogenic actions (mostly historical hunting, recent poaching, habitat loss and fragmentation, and unintentional translocation of individuals). In this study, we used data on mitochondrial DNA control region and 11 nuclear polymorphic microsatellite loci to assess the degree of population structure of C. acutus in South America, North America, Central America and the Greater Antilles. We used traditional genetic differentiation indices, Bayesian clustering and multivariate methods to create a more comprehensive picture of the genetic relationships within the species across its range. Analyses of mtDNA and microsatellite loci show evidence of a strong population genetic structure in the American crocodile, with unique populations in each sampling locality. Our results support previous findings showing large degrees of genetic differentiation between the continental and the Greater Antillean C. acutus. We report three new haplotypes unique to Venezuela, which are considerably less distant from the Central and North American haplotypes than to the Greater Antillean ones. Our findings reveal genetic population differentiation between Cuban and Jamaican C. acutus and offer the first evidence of strong genetic differentiation among the populations of Greater Antillean C. acutus

Estrutura populacional, razão sexual e abundância de Podocnemis sextuberculata (Testudines, Podocnemididae) na Reserva de Desenvolvimento Sustentável Mamirauá, Amazonas, Brasil

We studied turtles in the focal area of the Reserva de Desenvolvimento Sustentável Mamirauá from September 1996 through August 1998. The reserve is located in the western part of the Brazilian Amazon, between the Japurá, Solimões, and Auti-Paraná rivers, near the city of Tefé, in the state of Amazonas. In this study the population structure, sex ratio and abundance of Podocnemis sextuberculata were investigated. We intensively studied the population of turtles in the Jarauá river basin in order to determine population structure. We sampled turtles in different sectors in the focal area of the reserve for one month each year during July and August of 1997 and 1998. We captured the turtles using flag gill nets and trammel nets. The type of net and the size of the nets used influenced the size of the turtles captured. The nets used by the local fishermen were sexually selective in the capture of the turtles. Sevent-two percent of the P. sextuberculata captured were adults; 13% juveniles and 14.7% subadults. During the second year of the study we found a lower density of turtles in the five areas wich we sampled each years. The sex ratio of captured P. sextuberculata was 1.87 males per female

Seasonal movements of Podocnemis sextuberculata (Testudines: Podocnemididae) in the Mamirauá sustainable development reserve, Amazonas, Brazil

We studied the linear home range and seasonal movements of Podocnemis sextuberculata from September 1996 to December 1998 in the Mamirauá Sustainable Development Reserve located in the middle Solimões River, near Tefẽ, Amazonas, Brazil. We collected data on turtle movements and home range through mark and recapture and radiotelemetry, focusing on seasonal differences between periods of high and low water levels. Based on radiotelemetry of 6 females in the Jarauá River system, linear home range varied from 16.52 to 44.5 km. Nesting migrations from the Jarauá to the beaches of the Japurá River averaged 18.04 km. Males did not move significantly between captures. For conservation purposes, it is of critical importance to protect both the canals that the turtles use to travel between the lakes and the river as well as the deep holes in the river where mature turtles congregate during the dry season. © 2006 Chelonian Research Foundation

Factors affecting the number of caimans seen during spotlight surveys in the Mamirauá Reserve, Brazilian Amazonia

Between 1995 and 1998 we studied the effects of water level, moon phase, and site on the number of caimans observed in spotlight surveys in the Mamirauá Sustainable Development Reserve, Brazilian Amazonia. Multiple linear regression analyses including water level of the Amazon River and the moon phase explained 91 and 73% of the variance in number of Melanosuchus niger seen in spotlight surveys in Lago Mamirauá and Cano Mamirauá, respectively, and 60 and 76%, respectively, of the variance in the number of Caiman crocodilus seen. Water level had a statistically significant and negative effect on the number of N. niger and C. crocodilus seen. Moon phase had no significant effect on the number of C. crocodilus seen, but more N. niger were detected in Lago Mamirauá on nights with more moon light. The regression equations derived for Lago Mamirauá and Cano Mamirauá did not adequately predict the variation in numbers seen in 18 other water bodies in the Mamirauá Reserve. Analysis of covariance showed an interaction between water level and site on the numbers of N. niger and C. crocodilus observed in the spotlight surveys in these water bodies, indicating that the effect of water level depends on the site. In these analyses, moon phase did not have a significant effect on either species, and there was no interaction between moon phase and site. To monitor natural tendencies, or impacts (e.g., controlled commercial hunting), on caiman populations of Mamirauá Reserve, it will be necessary to undertake regular spotlight surveys in many water bodies of all types at a narrow range of water level to have confidence in the results. © 2008 by the American Society of Ichthyologists and Herpetologists

Estrutura populacional, razão sexual e abundância de Podocnemis sextuberculata (Testudines, Podocnemididae) na Reserva de Desenvolvimento Sustentável Mamirauá, Amazonas, Brasil

Population structure, sex ratio and abundance of Podocnemis sextuberculata (Testudines, Podocnemididae) in the Reserva de Desenvolvimento Sustentável Mamirauá, Amazonas, Brazil. We studied turtles in the focal area of the Reserva de Desenvolvimento Sustentável Mamirauá from September 1996 through August 1998. The reserve is located in the western part of the Brazilian Amazon, between the Japurá, Solimões, and Auti-Paraná rivers, near the city of Tefé, in the state of Amazonas. In this study the populacion structure, sex ratio and abundance of Podocnemis sextuberculata were investigated. We intensively studied the population of turtles in the Jarauá river basin in order to determine population structure. We sampled turtles in different sectors of the focal area of the reserve for one month each year during July and August 1997 and 1998. We captured the turtles using flag gill nets and trammel nets. The type of net and size of the nets used influenced the size of the turtles captured. The nets used by the local fishermen were sexually selective in the capture of turtles. Seventy two per cent of the P. sextuberculata captured were adults; 13 % juveniles and 14.7 % subadults. During the second year of the study we found a lower density of turtles in the five areas which we sampled both years. The sex ratio of captured P. sextuberculata was 1.87 males per female