Morphometric variation of the Asian Water Monitor Lizard (Varanus salvator) in different habitats in Peninsular Malaysia: a model analysis with machine learning

Abstract

The Asian water monitor lizard, Varanus salvator, is a widespread carnivorous reptile in Malaysia, but little is known about how habitat disturbance affects its morphology. This study analyzed 168 individuals across urban, agricultural, and forest habitats, using a Boruta algorithm and logistic regression to identify and validate morphological predictors of habitat. Allometric traits, including relative skull length, tail length, and thigh width, were better predictors of habitat differences than absolute measures such as snout-vent length (SVL) and snout-tail length (STL). Generally, urban and forest habitats exhibited similar variations in traits, but urban populations exhibited larger relative and absolute skull lengths, potentially linked to ecological or competitive advantages. In contrast, agricultural habitats displayed smaller traits, including relative tail length and thigh width, potentially reflecting pressures from predation or competition, resource limitations, or female-biased populations. Despite these differences, body condition and absolute size measurements were consistent across habitats, indicating populations in disturbed habitats maintain comparable sizes and energy reserves. While the species demonstrates adaptability to disturbance, further research is needed to explore ecological pressures in agricultural habitats and their potential impacts on the long-term fitness and population dynamics of V. salvator.