Relatively little has been documented about the seasonal activity, population biology, and foraging ecology of the yellow-bellied watersnake (Nerodia erythrogaster flavigaster). I studied a population of N. e. flavigaster in a riparian bottomland forest in eastern Texas. The male-to-female ratio was 1:1.23. Relative body mass did not differ between sexes but sampling was skewed toward juveniles. Relative tail length was sexually dimorphic with males having longer tails. Captures were highest in the spring months and significantly correlated with soil temperature under cover boards. Maximum prey size increased with snake size but adults still consumed small prey including anuran larvae, demonstrating a telescoping pattern of prey size selection. Approximately 50% of individuals with food had consumed more than one prey item. The data herein provide information regarding understudied aspects of N. e. flavigaster autecology and watersnake ecology in riparian forests.