We studied various aspects of the reproductive biology of the Magdalena River turtle (Podocnemis lewyana) during 2 nesting seasons in 2 locations in the Mompos Depression in northern Colombia. We monitored 53 nests; 22 that completed incubation in situ, 24 that were transferred to protected areas (transferred nests), and 7 that were constructed using eggs removed from females that had been consumed by local people (“oviductal” nests). For each nest, we registered the oviposition date, distance to the nearest body of water, soil type, vegetative cover, exposure to sunlight, depth to the first egg, and maximum depth of the nest chamber. We also quantified egg dimensions and clutch sizes, mean incubation temperatures and duration of incubation periods, hatching success rates, and sex ratios. Most nests were located within 15 m of the shoreline, in open or grassy areas with permanent exposure to sunlight, and in sandy soils. The 3 nest types (natural, transferred, and oviductal) did not differ in hatching success rates. In both seasons, the majority of the nests produced hatchlings of both sexes, but the sex ratios differed between the nesting beaches and seasons. Incubation temperatures influenced incubation periods and hatching success rates, but not hatchling sizes or weights. The management implications of the findings are discussed.

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