Head and venom gland morphology of common lanceheads Bothrops atrox vary intraspecifically and between habitats in the western Amazon of Brazil

Bothrops atrox is an endemic crotaline snake of the Amazon region, and due to its wide distribution and ample abundance it is the most responsible for snakebites that require medical attention in the North region of Brazil, with the state of Pará having the highest rate of incidences. B. atrox is also a key crotaline species in medical research and its venom has been intensively studied during recent years. As intraspecific variation of its venom between populations from floodplains and upland areas were reported and these differences in venom composition were likely related to a variable feeding ecology of the snakes inhabiting the different ecosystems. We confirmed that habitat variation influenced the external head and venom gland morphology of B. atrox i.e., in floodplains snakes had a smaller head size, venom gland size and mass compared to snakes from the other sampled habitats around western Pará.