Ontogeny of Sexual Size Dimorphism in Monitor Lizards: Males Grow for a Longer Period, but not at a Faster Rate
Abstract
We examined the ontogenetic trajectories of body weight and snout-vent length to analyze the emergence of sexual size dimorphism (SSD). Experimental animals were 22 males and 13 females of mangrove-dwelling monitors (Varanus indicus) hatched at the Prague Zoo.
They were regularly weighed and measured up to the age of 33-40 months, and subsequently sexed by ultrasonographic imaging. Our results confirm considerable sexual size dimorphism in the mangrove monitor.
The mean asymptotic body weight of males was nearly three times higher than that of females. As the body size of male and female hatchlings is almost equal, and the growth rate parameter (K) of the logistic growth equation as well as the absolute growth rate up to the age of 12 months do not differ between the sexes, size differences between fully grown males and females should be attributed to timing of the postnatal growth.