Boosting female hatchling production in endangered, male-biased turtle populations

Published source details Eisemberg C.C., Drummond G.M. & Vogt R.C. (2017) Boosting female hatchling production in endangered, male-biased turtle populations. Wildlife Society Bulletin, 41, 810-815.
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This study is summarised as evidence for the following.

	Action	Category
	Alter incubation temperatures to achieve optimal/desired sex ratio: Tortoises, terrapins, side-necked & softshell turtles Action Link

Alter incubation temperatures to achieve optimal/desired sex ratio: Tortoises, terrapins, side-necked & softshell turtles

A controlled study in 2003 on a sandy beach in Amazonas, Brazil (Eisemberg et al. 2017) found that covering six-tubercled Amazon River turtle Podocnemis sextuberculata nests with black plastic sheeting increased the proportion of female hatchlings, but decreased hatching success. River turtle nests covered with black plastic sheeting produced half the number of male hatchlings (1.5 of 5, 30% hatchlings/nest were male) compared to uncovered nests (3.3 of 5, 66% hatchlings/nest were male) and covered nests had lower hatching success (80%) than uncovered nests (92%). In September-November 2003, thirty turtle nests laid on a river-side beach (2 km long, 600 m wide) in a reserve were monitored from within 12 hours of being laid through to hatchling emergence. Fifteen of 30 nests were covered with a sheet of black plastic (0.1 mm thick covering a 2 m² area) in order to influence hatchling sex ratios. The remaining fifteen nests were monitored but not covered. Black plastic was removed after 50 days of incubation and nests were covered with nets to capture hatchlings as they emerged. Sex ratios were determined by sacrificing five hatchlings/nest and carrying out an examination.

(Summarised by: Katie Sainsbury)