A Spur with a Purpose
The platypus (Ornithorhynchus anatinus), a semi-aquatic mammal endemic to eastern Australia, is one of the few mammals to produce venom. This capability is exclusive to males, who possess a sharp, hollow spur on each hind ankle. These keratinous spurs, typically 15-18 millimeters long, are connected via a duct to a venom-producing crural gland in the upper thigh. While females are born with rudimentary spur buds, these structures drop off within their first year.
The venom system's primary role is not for hunting prey but for combat during the mating season. Venom production increases dramatically during this period, which corresponds with a rise in androgen hormones and testicular size. When threatened or competing with rivals, a male platypus will wrap its hind legs around a target, erect the spurs, and jab them inwards with considerable force. While the venom is potent enough to kill a dog, it is not lethal to humans. For humans, an envenomation causes immediate and excruciating pain, often described as worse than being hit by shrapnel, which can persist for weeks or even months and is notoriously resistant to morphine.