0000000000423981
AUTHOR
Michael Easter
Detection of a synthetic sex steroid in the American crocodile (Crocodylus acutus): Evidence for a novel environmental androgen
Endocrine-disrupting contaminants (EDC's) are well known to alter sexual differentiation among vertebrates via estrogenic effects during development, particularly in organisms characterized by temperature-dependent sex determination. However, substances producing androgenic effects typically lack potency when tested in laboratory settings and are virtually unstudied in field settings. Here, we assay levels of a synthetic androgen, 17a-methyltestosterone (MT), in a heavily male-biased population of American crocodiles in the Tempisque River Basin of Costa Rica based on the recent hypothesis that this chemical is an EDC in developing crocodilian embryos. The presence of MT was documented in a…
Cohort-Dependent Sex Ratio Biases in the American Crocodiles (Crocodylus acutus)of the Tempisque Basin
A male-biased sex ratio of 3:1 has been reported for a population of American crocodiles (Crocodylus acutus) in the Tempisque River Basin, Guanacaste, Costa Rica. If confirmed, this would constitute one of the largest male-biased sex ratios reported for any population of a member of the genus Crocodylus. Here, we examine the aforementioned population of C. acutus and report on sex ratios of hatchling, juvenile, and adult age classes within a sample of 474 crocodiles captured in the Tempisque Basin between May 2012 and June 2014. Hatchling sex ratio is exceptionally male biased (3.5:1), an imbalance that is maintained in juveniles but is reduced in adults (1.5:1). Mark–recapture data documen…