Zoological Studies

Vol. 49 No. 6, 2010

Ecology and Reproductive Characteristics of the Skink Sphenomorphus incognitus on an East Asian Island, with Comments on Variations in Clutch Size with Reproductive Modes in Sphenomorphus

Wen-San Huang*

Department of Zoology, National Museum of Natural Science, 1 Kuan-Chien Rd., Taichung 404, Taiwan

Wen-San Huang (2010) I describe the diet, and male and female reproductive cycles of Sphenomorphus incognitus, an oviparous skink in Taiwan.  Most individuals of S. incognitus were first observed in a leaf litter microhabitat or at the edge of a forest.  The diet of S. incognitus consists mostly of orthopteran insects.  Two prey categories, crickets and ants, numerically dominated the diet.  The stomachs of 2 lizards contained spiders, 2 lizards had eaten insect larvae, and 2 had eaten the blind snake, Ramphotyphlops braminus.  The mean snout-vent length (SVL) of adult males was 87.6 mm (n = 45), and that of females was 79.8 mm (n = 43).  Males had a significantly larger SVL than females.  Females exhibited spring and summer vitellogenesis, with parturition occurring from Mar. to July.  The onset of vitellogenesis was not correlated with the female liver mass.  Females produced 3-6 eggs per clutch, and clutch size was not correlated with the SVL.  Male testis mass showed significant monthly variations, with an increase commencing in Dec. and a peak maintained from Jan. to Apr.  Female and male liver masses did not coincide with the period of reproductive activity.  Clutch size variations in other Sphenomorphus groups were compared to those in S. incognitus.  Clutch sizes of oviparous skinks were not larger than those of viviparous ones, and clutch size relative to female SVL showed a positive correlation in oviparous skinks but not in viviparous ones.  Similarities of the reproductive cycle found in this study and other congeneric Sphenomorphus inhabiting temperate and subtropical areas of Taiwan might be explained by phylogenetic constraints.

Key words: Reproductive cycle, Clutch size, Lizard, Food habits.

*Correspondence: Tel: 886-4-23226940 ext. 510.  Fax: 886-4-23232146. E-mail:wshuang@mail.nmns.edu.tw