Life history characteristics of the Colombian Wood Turtle, Rhinoclemmys melanosterna (Gray, 1861), in the middle Magdalena River, Colombia

Abstract

Rhinoclemmys melanosterna is part of a clade of neotropical freshwater turtles known for their reduced clutch sizes with exceptionally large eggs. However, there are few studies of the life history of natural populations of these turtles to document what other aspects of their biology covary with this particular reproductive strategy. From 2009–2020, we used several capture techniques in different types of habitats in the middle Magdalena River region of Colombia to obtain captures/recaptures to estimate ontogenetic growth rates and sex ratios and to calculate body condition indices for each size class and sex. We also estimated the sizes/ages of sexual maturity of each sex, as well as generation time. Almost all individuals captured were adults, and the sex ratio was skewed towards females (1.85:1). Most recaptured individuals had moved a short distance (< 1000 m), although one female was recaptured 2800 m away from where she was first marked. Body condition indices of females diverged from those of males beginning at approximately 20 cm straight-line carapace length, with females almost always exhibiting higher scores. Using the von Bertalanffy Growth Model, we estimated that males reach sexual maturity earlier than females, at an approximate straight-line carapace length of 18–20 cm, whereas females mature at lengths of 20–22 cm, consistent with our body condition analysis. The average annual growth rate was 1.54 cm/year for males and 1.32 cm/year for females. The time required to reach the body size and/or the minimum age of sexual maturity was 3–4 years for males and 5–7 years for females.