Venom and spurs
The male platypus has a conspicuous spur (similar in size and shape to a dog’s canine tooth) located on the inner hind ankles. Adult spurs are typically 12-18 millimetres long and made of keratin, the structural protein found in feathers and human fingernails.
The spur is connected to a venom-secreting gland, known as the crural gland. Platypus venom is first produced when a male becomes mature, and more venom is secreted during the spring breeding season than at other times of year. Accordingly, it is believed that platypus spurs and venom have mainly evolved to help adult males compete for mates.
Platypus venom is a clear, slightly sticky fluid. It contains at least 19 different compounds which appear to have evolved quite independently from those found in snake venoms. Platypus venom is not life-threatening to humans, but can cause severe localised swelling and excruciating pain which gradually abates over a period of a few weeks.
At its worst, the pain is not very effectively relieved by standard analgesics such as morphine and is only made worse by application of ice packs. However, it can be treated successfully with drugs such as bupivacaine, which act by blocking nerve transmission.
Platypus spurs are normally held in a relaxed position, folded back against the inner ankle. Particularly during the breeding season, a spurring response will be initiated if the male is touched or stroked on its abdomen in the area between the hind legs. The hind feet are rapidly rotated outwards and upwards, pulling each spur erect and locking it into position against the lower limb bones. Both spurs are then jabbed inwards with great force, impaling any object in their path from two directions.
Although platypus are not particularly aggressive animals, great care should be taken whenever picking up either an adult male or an individual of unknown age and sex. In particular, such an animal should NEVER be supported from below. Instead, grasp the animal firmly by the END half of the tail (which cannot be reached by the spurs) before lifting it up and transferring it to a cloth bag, lidded box or other secure container.
When holding a platypus by the tail, it should be easy to determine if the animal is a male (based on the presence of conspicuous spurs on the ankles).
The appearance of male spurs changes with age. In the case of young juveniles, spurs are relatively short and stubby and covered in a sheath of whitish keratin. This covering gradually wears away, exposing the true spur which continues to grow. The spurs of subadult (second year) males can normally be distinguished from older individuals by the presence of a pink collar of skin which initially extends about one-third up the length of the spur. The collar skin gradually regresses and is very much reduced by the time that males mature at the age of two years.
Examples of a juvenile male spur (left) and subadult male spur (right)
Adult females of any age are easily told apart from males because they do not possess true spurs. However, juvenile females do have a tiny pointed brown or whitish spur typically 1-2 millimetres in length on their hind ankles. This structure generally disappears within about 8-10 months of a young female’s emergence from a nursery burrow, leaving behind a small pit in the skin.
Juvenile females have a tiny false spur (left) which is lost by the time a female is one year old (right).
Fenner, P.J., Williamson, J.A. and Myers, D. (1992). Platypus envenomation – a painful learning experience. The Medical Journal of Australia 157: 829-832.
Koh, J.M.S., Bansal, P.S., Torres, A.M. and Kuchel, P.W. (2009). Platypus venom: source of novel compounds. Australian Journal of Zoology 57: 203-210.