Abstract

Sexual dimorphism is expressed in many taxa as a form of resource partitioning and as a response to unique challenges faced by male and female organisms. We investigated this phenomenon for an arboreal green pit viper species, Trimeresurus macrops, previously suggested to display obvious sexual dimorphism. We evaluated seven external characters and scaled mass index (SMI) of 73 vipers (N = 32 males, N = 41 females) obtained during night surveys and opportunistic searches in north-east Thailand from January 2015–January 2017. We utilised Bayesian inference to investigate the influence of sex, gravidity, and rural habitat disturbance on sexual dimorphism of T. macrops, and we provide 95 % highest density intervals (HDI) for the difference in means (posterior distribution). We also present ecologically relevant probabilities of observing dimorphism for each external character and SMI by sex, gravidity (gravid or not), and habitat type (rural or forest). Females were larger than males in both forested and rural habitat, females in rural habitat were larger than forest females, and all males displayed a conspicuous white eye-stripe. When gravid females were excluded from analyses, probability of observing dimorphism drastically decreased. Knowledge of niche partitioning and the specific challenges encountered by males and females, gravid and non-gravid females, and individuals persisting in rural habitats will prove valuable for conservation and snakebite mitigation of T. macrops.