Male platypuses are among the few venomous mammals in the world. They have hollow spurs on their hind legs that are connected to venom glands. While the venom is not usually lethal to humans, it can cause severe pain and swelling. Male platypuses are thought to use these spurs primarily during mating season to compete with other males.
This trait is sometimes confused with echidnas, which are also monotremes. However, the venomous spur is a distinctive feature of the male platypus, not the echidna. Understanding this unique adaptation helps highlight just how unusual platypuses are in the animal kingdom.