Intra-Population Color Dimorphism of Ahaetulla prasina (Serpentes: Colubridae) in Northeastern Thailand

Abstract

Although Ahaetulla prasina is typically a cryptic green color, they have also been observed in brown, grey and orange-yellow morphs. We recorded observations of the A. prasina color morphs found in a population within the Sakaerat Biosphere Reserve (SBR), northeastern Thailand, between 2013 and 2017. We did not detect any green or brown morphs, showing that this population is dimorphic between grey (54%) and orange-yellow (46%) adults. We did not discern any geographic separation of the color morphs within this population, and sex did not determine color. We found four juveniles, all with brownish-grey bodies and yellow on their anterior dorsals. We observed one sub-adult, which was solid grey except for yellow on the top of the head. Our results suggest that this population may be genetically isolated due to the rapid development surrounding the SBR. Furthermore, color does not likely have a strong influence on adult fitness within this population. Our juvenile and sub-adult observations may indicate ontogenetic color shifts in this population of A. prasina. We recommend additional investigations into the relationship between color and A. prasina ecology. We further reason that the SBR A. prasina may be a good model population for snake genetic research in developing areas.