PLATYPUS
(Ornithorhynchus anatinus)  

Description
One of the worlds most unusual animals, the platypus was first described in 1799 by a British scientist, Dr George Shaw. His initial reaction to the original specimen provided by Governor John Hunter,  was that it was an elaborate hoax and he even attempted to dissect the carcass to prove his belief that someone had deliberately joined the beak of a duck to the head of a four footed animal.

In his scientific description, Shaw gave the name Platypus anatinus, from Greek and Latin words meaning "flat-footed, duck-like" respectively. However, when it became known that Platypus had already been used to name a group of beetles, a new term had to be adopted.  The official scientific name became and remains Ornithorhynchus  meaning "bird-like snout".  

Platypus are Monotremes.  The living Monotremes comprise the Platypus and two species of Echidna - or Spiny Ant-eater.  The name monotreme refers to the single (cloacal) aperture in the female through which faeces, urine and eggs are passed.  In other respects Platypus are typical mammals.  They are covered in fur, are warm blooded and suckle their young on milk which is secreted through pores on the belly. They do not have teats like other mammals.

The general appearance of a platypus is well known, a web footed, furred animal with a duck like bill.  The Platypus propels itself using its webbed forefeet.  The webbed hind feet are used only to steer or brake.   

The most distinct difference between males and females is size.  Males weigh  1.0 - 2.4kg with an average length of 500mm while females are usually smaller weighing  0.7 - 1.6kg with an average length of 430mm.

Distribution
Platypus occur from Cooktown in North Queensland to Tasmania. Platypus were successfully introduced onto Kangaroo Island, South Australia in 1940. They generally inhabit edges of subtropical to cool temperate rivers and freshwater lakes where burrows can be dug.  Burrows are dug above water level, amongst overhanging vegetation and tree roots.

Diet
The Platypus usually feeds at night, with peaks of activity for several hours after dusk and before dawn. During the day, it rests in a  burrow in the bank of the river or lake, but may spend some hours near the entrance to the burrow, basking in the sun and grooming its dense fur.

The Platypus appears to be opportunistic in its feeding habits and exists on Mayflies, Dragon/Damsel fly, beetles with aquatic larvae, Caddis flies, prawns, crayfish, small bivalve mussels, aquatic worms, small fish and fish eggs.

With both eyes and ears closed, the platypus relies on touch and electroreceptors located in the lower bill to capture food and navigate in the water.  Small pits can been seen in the lower bill if it is examined closely.  It is at the bottom of some of these pits that the electrosensors are located.

The Platypus feeds by probing in mud or silt on the bottom of rivers and freshwater lakes with a side to side movement of its sensitive, flexible, duck-like beak. While platypus have molars during the early stages of embryonic development, they are  toothless and grind their food between horny (keratinous) plates located over the gums.  They store the ground food in cheek pouches from where it is later sorted.

The male has a sharp, hollow, horny spur on the inside of the ankle. This is connected to a venom gland that produces a very strong toxin. The spur can be used in defence against predators, but the fact that it is restricted to the male—and that the gland reaches its greatest development in the mating season— suggests that it is normally employed in aggressive encounters between males.

Spur on a Male Platypus.

Females, like echidnas, have rudimentary spur buds which do not develop and do not have functional crural glands.  Spurs (or absence of spurs) are often used to identify sex and age of male animals can be determined by spur morphology (as per the diagram below).

a.             Juvenile 0-6 months old.
b.- c.       Juvenile 6 - 9 months old
               (sheath disintegrating).
d.            Sub-adult 9 - 12 months old.
e.            Adult 12+ months 
               (collar may be prominent up to 12 months).
f.            Old adult (spur may be worn down).

Venom
Adult, male platypus produce potent venom in a crural gland located immediately behind and above each kidney.  The glands excrete into a tortuous duct which runs through the muscles behind the femur to connect with a canal at the base of a horny, curved, sharp spur inside each leg.  On arousal the spurs erect and are plunged deeply into the source of irritation by thrusting inward with both hind legs, releasing up to 4 ml of venom.  Venom is produced most abundantly, if not exclusively, during late June to late February, coincident with the breeding season, so is probably testosterone linked.  Immature males have sheathed developing spurs but do not produce venom and are thus disadvantaged in territorial disputes.  

Spurred victims experience immediate and increasing excruciating pain with rapid swelling and discolouration of tissues surrounding the wound.  The pain is not alleviated by analgesics, even intravenous morphine.  However, it is relieved by nerve blocks central to the site of spurring.  Excretion of dark to black urine indicative of intravascular haemolysis may occur for days after spurring.  Incubation of red blood cells from one victim showing strong local tissue discolouration and haemoglobinuria resulted in haemolysis in the absence of added potassium, characteristic of haemolysis by the enzyme, phosphilase D, found only in some snakes, including the Australian Tiger Snake.  This aspect of the toxic syndrome requires further study.

An antibody specific for NSW platypus venom has been demonstrated in the serum of a victim spurred two years ago in Queensland so an antivenene is possible.  

Breeding
Platypus are sexually mature at 2 years old.  Mating occurs once a year, the season beginning in August in the warmer northern parts of the range and in October in the southern part. The female usually lays two eggs and incubates these against her abdomen for about two weeks in a blocked-off nest at the end of a long breeding burrow. Hatching occurs in late October to early November and the one or two offspring are suckled for four to five months. 

Conservation Status and Threats
The Platypus is under protection of the Australian government .  Though common, it is a potentially vulnerable species.

Mortality is still to be thoroughly researched however it is believed that there is some predation by foxes, goannas, birds of prey and possibly eels.  Other factors include starvation and/or heat stress in dispersing juveniles and human activities, especially fish netting and dam building.

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