PLATYPUS (Ornithorhynchus anatinus)

(plural: platypuses)

The echidna and the platypus are the only two existing monotremes (egg-laying mammals) in the world. Believed to originate some 200 million years ago, these furry mammals retain certain reptilian skeletal features. They are a strange mix with such unusual features such as the duck bill and webbed feet.

The first platypus to be scientifically described came from the banks of a lake near the Hawkesbury River, near Sydney, in 1797. The British Museum received a stuffed platypus in 1798, but the scientists thought it was a fake. Later they were to learn that it layed eggs!

The platypus is found in lakes, streams and rivers of eastern Australia, from Tasmania to south of Cooktown in Queensland. They have also been introduced to Kangaroo Island in South Australia. Whilst common in these areas, because of their shyness they are difficult to observe but may be seen partially submerged near the surface.

The platypus is wholly protected throughout Australia.
The platypus has been recorded to live to 16 years in the wild, the longest lifespan for a platypus in captivity is 17 years. Platypuses are hard to care for in zoos.

DESCRIPTION:
The body shape of the platypus resembles that of a mole or otter with a broad, flat tail similar to that of a beaver. The male grows to a maximum of 24 inches(60cm) and the female 20 inches(50cm).

Platypus fur is extremely fine but dense. It has two layers - a woolly undercoat and longer, shiny outer guard hairs - which together trap a layer of air next to the skin, keeping most of the animal's body dry even when diving. The fur is deep brown on the back and sides of the head, body and upper surfaces of the limbs. The underside is a golden colour although silky grey is not uncommon. The fur on the broad flat tail is coarse and bristly.

The soft hairless bill resembles a duck bill. It is not hard like that of a bird, but is an elongated snout covered with soft moist leathery skin which contains sensitive nerve endings.

The eyes are small, and there are no external ears, but it has keen senses of sight and hearing. Both the earholes and the eyes are set into a deep fold in the skin. The ears and eyes are closed by this fold of skin when diving, making the platypus both blind and deaf once it submerges. While floating at the surface, the platypus is always alert. Both sight and hearing are then very acute.

The skin of the webbed front paws extends beyond the long claws. In the water they expand and act as broad paddles. Out of the water the skin folds under the foot, making it easier for the animal to walk and use its strong claws for digging burrows. The webbing on the hind foot does not extend beyond the bases of the claws. The hind feet, together with the tail acting as a rudder, provides stability and directional control.
The male has a poisonous, horny spur, about half an inch (1cm) long on the inside of each hind leg. This is connected to a poison gland. A scratch from this may cause a painful swelling in humans, no deaths have been recorded.

DIET AND HABITAT:
A platypus must eat large quantities of food to survive - at least half their body weight every day.
The platypus diet consists of insect larvae, snails, yabbies, worms, tadpoles and other fauna and shellfish. They also occasionally eat small frogs, small fish and fish eggs. Its sensitive bill detects and uncovers its prey in the mud at the bottom of rivers, around boulders, under logs and among reeds. It snaps up the food, along with grit to aid in grinding, stores it in its cheek pouches, and then comes to the surface to feed. Adult platypuses do not have teeth, instead they have horny plates to crush the food. Young platypuses have molar teeth to chew their food but these are replaced by the horny ridges as they mature.

The platypus, when searching for food, can stay submerged for periods of one to five minutes. When floating on the surface it can difficult to see because it lies very low in the water and looks like a piece of dark waterlogged wood.

Platypuses are solitary animals that only come together to mate, however they can be found living in close proximity.
They are most active during the early morning and late evening. They spend up to 17 hours a day resting out of the water in an underground burrow, and only spend about two hours in the water feeding. If they stay in the water for too long their fur becomes very heavy and waterlogged and they could drown.
Platypuses have occasionally been found sleeping inside a hollow log at the edge of the water or within a pile of branches.

Burrows are usually 4.5 to 9 m in length, oval shaped and are constructed just above the water line of rivers and streams, usually near their feeding areas and often obscured by vegetation. The main tunnel may change direction several times. The main living burrow is short and simple while a nesting burrow can be as deep as 20 metres and is lined with grass. After mating, the female platypus digs an elaborate nesting chamber, lined with leaves and the entrance plugged with soil. This burrow is maintained by the female.

REPRODUCTION:
Mating occurs during spring and is initiated, in the water, by the female. Egg-laying, incubation and hatching take place in the nesting burrow. The female alone occupies a burrow during the breeding season, the burrow being plugged with earth at intervals. The interval between fertilisation and egg-laying is unknown, but has been suggested between 12-14 days, with a further 10-12 days before the egg hatches.

Usually two soft, whitish eggs are laid. No bigger than sparrow eggs, they are usually stuck together. The female may curl around them or lie on her back to incubate the eggs on her abdomen. The newly hatched platypuses are 2.5cm long, blind and have no fur. The female uses its tail to guide the young to its abdomen enabling them to nurse. Although the mother does not have nipples, milk seeps from the mammary pores and the young suck it from the hair. After four months, the young emerge from the burrow. Two weeks later they are independent.

Male platypus do not help to raise the young.

PREDATORS:
Hawks, eagles and owls occasionally capture platypus in the water. Carpet pythons, goannas and Australian water-rats may attack young platypus in the burrow. The absence of platypus in the far north of Queensland may be due to crocodiles. Foxes, dogs and cats have also become enemies of the platypus. Platypuses also die as a result of becoming trapped in litter (from humans) such as fishing lines or plastic six-pack can holders.