Common names: fer-de-lance, terciopelo (more).Bothrops asper is a venomous pit viper species ranging from southern Mexico to northern South America. Sometimes referred to as the "ultimate pit viper", these snakes are found in a wide range of lowland habitats, often near human habitations. Its proximity to human habitations is likely the reason why it is considered more dangerous to humans than others. This species is the main cause of snakebite incidents within its range.