Oophaga pumilio (Strawberry poison-dart frog),
while not the most poisonous of the rainforest dendrobatids,
is the most toxic member of its genus.
Their 'poison', however, is not inherent.
Rather, it is a by-product processed from their specialized diet:
small arthropods, primarily formicine ants.

"It's the Ants!" - Dr Robert Campbell (Sean Connery) 'Medicine Man'