One possible exception is the puff adder, a venomous African snake. It sits in ambush for weeks at a time, and protects itself by visually blending into its environment. But somehow, it seems to blend in chemically, too. In 2015, Ashadee Kay Miller found that keen-nosed animals, including dogs, mongooses, and meerkats, can’t detect a puff adder, even when they walk over one. Dogs can detect the scent of shed skin, but for reasons that no one understands, the living snakes are undetectable to their noses.
