What is the most venomous snake in Costa Rica?

The Bothrops asper, a pit viper. Is is responsible for 46% of all bites and 30% of all hospitalized cases; before 1947, the fatality rate was 7%, but this has since declined to almost 0%, mostly due to the Clodomiro Picado Research Institute, responsible for the production of anti-venom and scientific research on serpents and their venoms, as well as educational and extension programs in rural areas and hospitals.

In the Columbian states of Antioquia and choco, it causes 50-70% of all snakebites, with a fatality rate of 5%.