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

Human pressure, distribution and abundance of crocodiles () in the Cojedes River System, Venezuela

[email protected] analítica--semestra

Population decline of the Orinoco Crocodile (Crocodylus intermedius) in two sectors of the Cojedes River system, Venezuela

La sobreexplotación de Crocodylus intermedius entre las décadas de los 20 y 60 del siglo pasado, diezmó las poblaciones a niveles críticos o incluso hasta eliminarlas en algunas localidades y regiones. En la presente investigación, evaluamos la población del Sistema del río Cojedes (SRC), catalogada como la más importante para la conservación de C.intermedius. En el 2009, mediante 16 conteos nocturnos determinamos la abundancia y estructura poblacional en dos sectores del SRC, La Batea-Confluencia (LBC 6,5km) y Confluencia-Caño Amarillo (CAM, 14,2 km). Adicionalmente, comparamos los índices poblacionales estimados en el 2009 con los reportados para los años 1991-1997 y 2006. En el año 2009, la abundancia máxima la estimamos en 5,4 y 3,5 individuos/km para LBC y CAM respectivamente. Hubo diferencias significativas en la abundancia entre los sectores estudiados, con un mayor número de caimanes en el sector La Batea Confluencia (LBC H= 11,29; P=0,003 y CAM H=11,43; P=0,003). La población mínima de caimanes se estimó en 73 individuos, cifra 31% menor que la reportada entre 1991-1997, 42% menor que la señalada para 1997-1999 y 11% menor que la de 2006. La estructura poblacional estuvo dominada por juveniles Clase II, seguida de adultos Clase V, posiblemente influenciada por las liberaciones realizadas por el programa de conservación de la especie (604 individuos), y porque la presencia humana en estos sectores es menor, lo que posibilita que individuos de mayor tamaño habiten sin ser [email protected]@cantv.netsemestralThe overexploitation of Crocodylus intermedius between the decades of the 20s and 60s of the last century decimated its populations to critical levels or even extirpated them in some areas and regions. In the present study, we evaluated the population of the Cojedes River System (CRS), ranked as the most important for the conservation of C. intermedius. In 2009, with 16 night light-counts we determined abundance and population structure of crocodiles in two sectors of the CRS, The Batea-Confluencia (LBC 6.5 km) and Confluencia-Caño Amarillo (CAM, 14.2 km). In addition, we compared the estimated population indices with those reported for the years 1991-1997 and 2006. In the year 2009, the maximum abundance was estimated in 5.4 and 3.5 individuals/km for LBC and CAM, respectively. There were significant differences in abundance between the sectors studied, with a greater number of crocodiles in La Batea-Confluencia (LBC H = 11.29, P = 0.003 and CAM H = 11.43, P = 0.003).The minimum population of crocodiles was estimated at 73 individuals, a figure 31% lower than that reported in 1991-1997, 42% lower than that calculated for 1997-1999 and 11% lower than in 2006. The population structure was dominated by juveniles Class II, followed by adults (Class V), possibly influenced by the releases made by the conservation program for the species (604 individuals), and because the human presence in these sectors is lower, which enables larger individuals inhabit undisturbed

Hematological values of juvenile Orinoco crocodiles (crocodylus intermedius) in Venezuela

Se analizaron los valores hematológicos de muestras de sangre de 81 Crocodylus intermedius, de ambos sexos, con edades comprendidas entre los 6 meses hasta dos años y medio. Setenta y dos de los individuos habían sido mantenidos desde su nacimiento en cautiverio y nueve fueron recapturados en el medio silvestre donde habían sido liberados entre 5 y 18 meses antes. Los promedios de longitud total (LT), longitud corporal (LC) y peso fueron 761 mm, 399 mm y 1.567 g, respectivamente. El promedio de hemoglobina fue de 8,57g/dL, el hematocrito 24,76% y leucocitos totales 6.605 por mm3. No hubo diferencia entre sexos en los parámetros señalados. El número de leucocitos mostró una leve tendencia a disminuir con el tamaño de los animales. El conteo diferencial de leucocitos dio como resultado una mayor proporción de heterófilos (55,8%), seguido en importancia por los linfocitos (31,8%). Se consideran de gran importancia estos datos, dado el peligro crítico en que se encuentra esta especie y la difícil consecución de constantes fisiológicas patrones para el C. intermedius. Se pretende con ellos brindar una guía o patrón comparativo a los médicos veterinarios y biólogos que trabajen en los planes de conservación del caimán del Orinoco en zoocriaderos o zoológicos, para diagnosticar enfermedades en las poblaciones bajo su [email protected] hematological values of blood samples taken from 81 Crocodylus intermedius of both sexes and from six months to two and a half years of age were analyzed. Seventy two of these crocodiles came from a rearing facility, where they have been maintained since they hatched from eggs, and the remaining nine were recaptured from the wild, where they have been released 5 to 18 months before. The average total length (TL), snouth-vent length (SVL) and weight was 791 mm, 399 mm and 1,567 g, respectively. Mean hemoglobin value was 8.57 g/dL. The heamatocrit average 24.76% and leukocytes counted to 6,605/mm3. There were no differences between sexes for the above mentioned values. Leukocyte counts showed a slight trend to decrease with crocodile’s size. The differential count of leukocytes resulted in a higher proportion of heterophils (55.8%) followed in importance by lymphocytes (31.8%). These data are considered as relevant, since the species is considered as critically endangered and due to the lack of physiological values that could be used as standard for comparisons for C. intermedius. They could be used by veterinarians and biologists working with conservation programs for the species in rearing facilities or zoos, to diagnose deceases in the species they work with

Conservation status and regional habitat priorities for the Orinoco crocodile: Past, present, and future

Conservation of large predator species has historically been a challenge because they often overlap in resource utilization with humans; furthermore, there is a general lack of in-depth knowledge of their ecology and natural history. We assessed the conservation status of the Orinoco crocodile (Crocodylus intermedius), defining regional habitat priorities/crocodile conservation units (RHP/CCU) and regional research priorities (RRP) for this species. We also estimated a species distribution model (SDM) to define current suitable areas where the species might inhabit and/or that might be successfully colonized. The SDM area obtained with a suitable habitat probability ≥ 0.5 was 23,621 km. Out of 2,562 km are included within protected areas in both Colombia (1,643 km) and Venezuela (919 km), which represents only 10.8% of C. intermedius' potential range. Areas such as Laguna de Chigüichigüe (flood plain lagoon) exhibited an increase in population abundance. In contrast, localities such as the Cojedes and Manapire Rivers reported a significant reduction in relative abundance values. In Colombia, disparity in previous survey methods prevented accurate estimation of population trends. Only one study in this country described an increase over a 13 years span in the Ele, Lipa, and Cravo Norte River populations based on nest surveys. We defined 34 critical areas (16 in Colombia, 17 in Venezuela, and one covering both countries) where we need to preserve/research/monitor and/or generate management actions, 10 RHP/CCU (six from Venezuela and four from Colombia) and 24 RRP (11 from Venezuela, 12 from Colombia, and one in both countries). Caño Guaritico (Creek) and the Capanaparo River in Venezuela and the Ele, Lipa, Cravo Norte River System and the Guayabero River in Colombia were defined as areas with the most optimal conditions for long-term preservation and maintenance of C. intermedius populations. We conclude that the conservation status of this species is still critical, which implies the necessity to increase efforts to recover the species, especially in Colombia, to guarantee its survival as a structural and functional component of the ecosystems it inhabits.Peer Reviewe

Regional Habitat Priorities/Crocodile Conservation Units (RHP/CCU) and Regional Research Priorities (RRP).

<p>RHP/CCU and RRP defined through the Orinoco crocodile range based on current knowledge about the species as well as management actions taking place and relative abundance patterns.</p

Species Distribution Model (SDM) for the Orinoco crocodile.

<p>SDM depicting: (A) all suitable areas available in both Colombia and Venezuela based on the variables assessed as well as the isocline at 350 m asl and the spatially rarefied geolocations; (B) the suitable area including absence data, the 0.2 threshold area, and all the occurrence data used in this study; (C) the most suitable distribution model under the 0.5 threshold area, highlighting areas inside (yellow) and outside (light green) of the Orinoco basin.</p

Regional Habitat Priorities/Crocodile Conservation Units (RHP/CCU) and Regional Research Priorities (RRP) variables and classifiers.

<p>Regional Habitat Priorities/Crocodile Conservation Units (RHP/CCU) and Regional Research Priorities (RRP) variables and classifiers.</p

Relative abundances of the Orinoco crocodile populations in Venezuela without specific time information.

<p>Relative abundances of the Orinoco crocodile populations in Venezuela without specific time information.</p