Population characteristics and egg production of the yellow-margined box turtle, Cuora flavomarginata flavomarginata, in northern Taiwan

From May 1996 to September 1997, we investigated population and reproductive characteristics of Cuora flavomarginata flavomarginata in the Feitsui Reservoir Protected Area, northern Taiwan. Of 288 turtles captured, 174 were females, 95 were males, and 19 were unsexed juveniles. The overall and adult sex ratios were significantly biased toward females. Whether by baited trap or by hand, the capture frequency was significantly female-biased. The population at Feitsui was mainly composed of adult individuals (78.1%). The average body size of adult females was larger than that of adult males. Radiographing revealed that females were gravid from mid-April through mid-July, with the highest percentage in May. Periodic radiographing of radio-tagged females suggested that C. f. flavomarginata laid one or two clutches between early May and mid-July. Carapace length of gravid females ranged from 138.0-174.8 mm (mean = 155.1). Clutch size varied from 1-3 and averaged 1.6. Egg size was positively correlated with female body size, but clutch size and annual clutch frequency were not. Turtles in the larger size classes (155.0-169.9 mm carapace length) were more likely to be found with shelled eggs than the smaller-sized turtles. Larger females were also more likely to lay eggs in both of the consecutive nesting seasons. We identified seven turtles that reproduced in both years.