Sexual Dimorphism of the Three Pit Viper Species (Gloydius brevicaudus, G. ussuriensis, G. intermedius) in South Korea

Sexual size dimorphism in snakes is closely related to mating behavior and fecundity selection. It provides important information on animal morphology and evolutionary ecology because it allows us to identify key morphological and functional traits between sexes and infer intraspecific competition. In this study, we measured the morphological characters of 147 individuals of three pit viper species stored in the archive of the National Institute of Biological Resources of the Ministry of Environment and confirmed interspecific differences and sexual size dimorphism of each species. We also identified important characters affecting identification using linear discriminant analysis. The results showed that the three pit viper species differed in body and head morphology, and the number of dorsal scale rows was the most important character for species identification. It was found that female red-tongued pit vipers and short-tailed pit vipers were larger than males of each species, while male Central Asian pit vipers were larger than females. Characters related to tail length and head length were confirmed as important characters for interspecific sex discrimination. We compared characters related to head morphology between sexes to find that red-tongued pit vipers showed differences in most characters, while short-tailed pit vipers and Central Asian pit vipers did not. Therefore, short-tailed pit vipers and Central Asian pit vipers are expected to have strong intraspecific competitive pressure. In future studies, it will be necessary to conduct a detailed research on intraspecific competition of short-tailed pit vipers and Central Asian pit vipers with little morphological differences between sexes by examining resource utilization (e.g., food sources and habitats) and ecological niche.