Endoscopic imaging of gonads, sex ration, and temperature-dependent sex determination in juvenile captive-bred radiated tortoises, Astrochelys radiata

Published source details Kuchling G., Goode E. & Praschag P. (2013) Endoscopic imaging of gonads, sex ration, and temperature-dependent sex determination in juvenile captive-bred radiated tortoises, Astrochelys radiata. Chelonian Research Monographs, 6, 113-118.
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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
	Breed reptiles in captivity: Tortoises, terrapins, side-necked & softshell turtles Action Link

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

A before-and-after study in 2006–2009 at a captive breeding facility in southern California, USA (Kuchling et al. 2013) found that radiated tortoise Astrochelys radiata most eggs incubated at 28.9°C or higher produced female hatchlings. Results were not statistically tested. At 28.9°C, twenty-three of 25 hatchlings (92%) were female, and at 30°C, all 29 hatchlings were female. Eggs from captive tortoises were collected and incubated in modified wine coolers at 28.9°C in 2006–2007, and at 30°C in 2008–2009. Eggs were incubated in vermiculite and water at a 2:1 ratio.

(Summarised by: William Morgan)
Breed reptiles in captivity: Tortoises, terrapins, side-necked & softshell turtles

A study in 2001–2009 at captive breeding facilities in Georgia and southern California, USA (Kuchling et al. 2013) reported that radiated tortoises Astrochelys radiata bred successfully in captivity. In 2001–2009, the captive breeding programmes produced at least 75 juvenile tortoises. Sixty-seven were female and eight were male. Incubation periods for those eggs that hatched in 2006–2009 ranged from 90–120 days. In 2001–2004, tortoises were maintained in a captive breeding facility in Georgia. Tortoises were then moved to a new facility in southern California, where they had access to both indoor and outdoor enclosures. One group of older, wild-caught tortoises were managed to maintain high genetic diversity (details not provided). Another group of captive-born tortoises could choose mates freely. In 2006–2009, eggs were incubated in vermiculite and water at a 2:1 ratio at 28.9°C or 30°C.

(Summarised by: William Morgan)