Population Ecology of the Lizard Japalura swinhonis formosensis (Sauria: Agamidae) in Taiwan

Abstract

The population ecology ofJapalura swinhonisformosensis in Taiwan was studied by capture-recapture method from February 1979 to April 1980. The characteristic growth rate of the male lizards is 0.005 mm per day. Male hatchlings of early clutches require 142 days to reach their mature snout-vent length (SVL), those of late clutches 262 days. The characteristic growth rate of the female lizards is 0.004 mm per day. Female hatchlings require 347 days to reach adult size. Growth rates after the third year for both sexes practically cease. Mean home range size of males is 33.47 m2 and is not significantly different between the breeding and non-breeding season. Few home ranges of males overlap. Only large adult males over 73 mm SVL establish territories. Male lizards appear to carry out rout defense concurrently with normal feeding as well as specific site defense. Mean home range size of females is 11.46 m2. Most of the home ranges of females are entirely or partially within those of males. The mating system appears to be polygynous. Monthly population size and survivorship of adult lizards are fairly stable. Mean population sizes of adult males and females are 210.3 and 224.7 lizards per hectare, respectively. Survivorship of males and females is 82.3% and 82.5%, respectively. On the average, second year adult males make up 48.4% of the total male individuals, the third year adult males, 39.0%, and fourth year adult males, 4.1%. Second year adult females make up 28.8% of the total female individuals, third year adult females, 47.1%, and fourth year adult females, 13.4%. Sex ratios indicate that males predominate over females in the first two years, and the opposite is true for third and fourth year individuals. Males and females utilize the habitat horizontally but at different heights; the same is true of the different SVL classes of males. This habitat partitioning results not so much from specialization for food resources, as from the social interactions among males. Perch diameter does not appear to play any significant ecological role.