Are Duck Billed Platypuses Poisonous

 he platypus is one of a very few venomous mammals. Two species of Caribbean solenodon and a few species of shrew use poisonous saliva to subdue prey, often larger than themselves, but the platypus has something completely different and of unknown function.

Rear-ankle spurs are found in all three species of monotreme. With their associated glands, they are known as the crural system. In females of all species of monotreme the spur is lost during the first year of life. Although the spurs and glands persist in male echidnas of both species, echidnas do not seem to use the system to inject venom; the platypus does.

Changes in the structure of the spur in male platypuses can be used to age animals up to 15 months after they have left the breeding burrow. Fully grown adult spurs are around 15 millimeters (2 inch) in length, can be everted away from the ankles, and can be driven into an object by the action of the muscles of the rear legs.

The puncture alone is painful, but the venom injected can lead to symptoms ranging from local pain and swelling to paralysis of a whole limb in humans.

When the species was hunted for its pelt, animals were stunned by a heavy caliber shot fired under them in the water and a gun dog was sent out to retrieve the animal. There are numerous stories of dogs being killed by the platypus recovering and spurring them in the muzzle.

The nature of the venom is unknown, as is its function. An early naturalist suggested that the male used his spurs to subdue females during mating, but more recent observations indicate that the female may initiate much of the courtship and need no such subduing

The glands associated with the spur advance and recede with the testes during the breeding season, and it is assumed that their function is related to breeding. Certainly, males are more aggressive toward each other and toward any other animals at this time of the year.

The social system in platypuses is completely unknown, but the retention of the crural system only in male platypuses seems to indicate that it may be used in establishing territories or access to mates during the breeding season. In the wild animals presumably have the opportunity to escape from such encounters, which have been known to result in deaths in captivity. The spurs certainly represent a deterrent to predators, but their loss in females suggests that this is not their primary function.