A Brazilian scientist got more than he bargained for when a frog he was handling turned out to be venomous. The venom was injected by concealed spines located in the animal’s upper lip. After five hours of agony, the biologist recovered, and was a lot more cautious about picking up strange frogs. Good thing, because his research group soon discovered another even more venomous frog—this venom was worse than that of a pit viper. Several species of poisonous frog are known, but these are the first discovered venomous frog species—the poison is injected, not present in the animal’s tissues. And there are even more unlikely venomous critters out there!

Everyone knows about certain venomous snakes and fish, but amazingly there are a couple of venomous mammals. Ounce for ounce, the nastiest is the tiny short-tailed shrew. Shrews are rodents; their bites cause agony to humans, and much worse for their prey. Shrew venom immobilizes smaller animals such as beetles or worms, allowing the shrew to stash their helpless prey until they are ready to eat it. Since the prey are immobilized, not dead, the meal stays fresh.

Shrew venom is so potent that shrews can even tackle mice, animals about the same size. In one experiment, mice were placed in an enclosure with a hungry shrew. A small mouse with a head bite succumbed in just over a minute, but for most extremity bites in larger mice, the venom was not fatal. That is not to say that most of the mice survived the experiment; stunned and semi-conscious, many mice that survived their bite were eaten hours later. So that’s shrews.

Perhaps the unlikeliest venomous animal is the duck-billed platypus. Male platypuses have two spurs extending from their hind legs, and woe to anyone or anything who grabs one. Platypus venom shares chemical characteristics with the venom of both spiders and green mamba snakes. They use the spurs primarily during contests for mates, but presumably they function in self-defense also, at least against biologists.

The moral of the story, for biologists and amateurs alike, is to avoid assumptions. Just because an animal is small, cute, or unassuming does not mean it isn’t fierce. Frog, shrew, platypus—handle with extreme care. Better yet, don’t handle at all!