Yvette Cooper may think so, and use of epibatidine may seem exotic, but experts say situation is more ambiguous Yvette Cooper may think so, and use of epibatidine may seem exotic, but experts say situation is more ambiguous It was a very particular choice of weapon, but experts say it remains unclear whether the dart frog toxin used to kill the Russian opposition leader Alexei Navalny was intended to convey a message. Known as epibatidine , the poison is produced by wild dart frogs native to