An adult male platypus is around 500mm long and 1-2.2 kilograms in weight. The female is smaller at 450mm about 0.7-2 kilograms in weight. The duck- like bill is covered in bluish, leathery skin and the fur is a velvety dark brown velvety on the back and creamy yellow underneath The feet are webbed.
When not fossicking in a stream or river, the platypus spends the rest of its time in a short, simple burrow in the side of the bank often under a tangle of tree roots. The entrance is about one to two metres above water level. It is usually distinguishable from other holes in the river banks by its characteristically oval section and it may be double-ended.
Much of the diet includes adult and larval invertebrates such as worms, yabbies, and insect larvae but it occasionally eats small vertebrates. The smaller prey are sifted from the mud, silt and gravel in the bottom of their habitats using electro-magnetic receptors in the bill.
The female platypus makes a second burrow for nesting. It may be up to 20 metres long. When the female enters the burrow to lay her eggs she blocks the burrow every few metres to keep out floods and predators and to retain heat. The female lays 2-3 white eggs in a nest consisting of dry grass and leaves. The eggs hatch after two weeks. The young remain in the nest for four months emerging in December or January. At that time they are about 300mm long.
Activity usually takes place in the early morning or late afternoon but this may vary somewhat depending on season, temperature, etc. There have been reports of combat between individual platypus suggesting they may be territorial in specific areas. An important element of their behaviour is meticulous grooming; this mainly occurs on a log or rock or sometimes in the water.
Platypus only live in suitable bodies of relatively undisturbed freshwater, which are under increasing demand for other uses and are being drained and polluted for development and land clearing. Stream and river bank improvements, irrigation, dams, chemical pollution, fish netting and trapping are among the hazards that may alienate habitat and lead to the reduction or extinction of local populations. Although the platypus is still common in much of it’s present range, it must be regarded as vulnerable.