Abstract

Herpetofaunal diversity in tropical canal ecosystems remains understudied, particularly in Thailand, where extensive networks of artificial waterways modify natural habitats. This study examined amphibian and reptile diversity along the Lam Takhong Canal, Pak Chong District, Nakhon Ratchasima Province, Thailand, and investigated relationships between environmental drivers and species diversity using Visual Encounter Surveys at six stations (twelve sampling points) spanning upstream, midstream, and downstream zones. Environmental parameters, including air temperature, water temperature, soil temperature, relative humidity, pH, ammonia, and nitrate, were measured concurrently, and relationships were analyzed using Pearson correlation, multiple regression, and one-way ANOVA. A total of 463 individuals representing 45 species were recorded (326 amphibians from 19 species; 137 reptiles from 26 species), including the Thailand-endemic Khorat snail-eating turtle (Malayemys khoratensis). Water pH and ammonia were significantly and positively correlated with species richness and abundance (r = 0.741 and 0.795, respectively; p < 0.05), while water temperature showed a marginally significant negative correlation with richness (r = −0.531, p = 0.075). Air temperature and humidity showed no significant associations. A multiple regression model incorporating environmental predictors explained 75% of the variance in species richness (R² = 0.749). These findings indicate that water quality, rather than microclimatic conditions, is the principal determinant of herpetofaunal diversity in this tropical canal ecosystem, with implications for water-quality management and habitat conservation in irrigation canals across rapidly developing agricultural landscapes in Southeast Asia.