DUCK-BILLED PLATYPUS – [Ornithorhynchidae]

PHYSICAL CHARACTERISTICS

A platypus, at first glance, resembles an otter with a duck’s bill

on its face and a beaver’s tail in back. An adult platypus, about

the size of a house cat, weighs from 3 to 5 pounds (1.5 to 2.5

kilograms), its adult head and body length runs 12 to 18 inches

(30 to 45 centimeters), and the tail adds another 4 to 6 inches

(10 to 15 centimeters). Males are larger than females.

The snout, despite its duckbill shape, is soft, moist, and rub-

bery in texture, not hard like a bird’s beak. The bill has an

upper and lower section, like that of a mammal or bird, and

the jaw hinging and motions are like those of mammals. The

nostrils are set close together on the top of the upper bill.

The word “platypus” means “flat feet,” referring to the

animal’s webbed, somewhat ducklike feet. The scientific name,

Ornithorhynchus anatinus, means, in Latin, “bird-snout, resem-

bling a duck.” The plural is “platypuses” or just “platypus.”

Most of the body is covered with fine, soft fur. The pelt color

varies from dark amber to very dark brown on the platypus’s

back and sides, and from grayish white to yellowish brown on

the underbelly. Platypus fur is fine, soft, and dense, with up to

900 hairs per square inch of skin. The fur has two layers, an

undercoat with a woolly texture and an overcoat of coarser hair.

As the platypus dives, the two fur layers trap a layer of air next

to the skin, thus keeping the body dry and helping to insulate

it against cold while the platypus swims, often throughout the

night, and sometimes in temperatures close to freezing.

The body is somewhat flattened and streamlined. The limbs

are short and muscular. As in other monotremes, the limbs of

the platypus are set in a permanent push-up position, the up-

per limb bones extending out from the sides of the body, hori-

zontal to the ground, the lower limb bones going straight down.

Although an excellent swimmer, the platypus is clumsy when

trying to walk on land, and seldom does so anyway, except

within its tunnels, since it burns up twice as much body energy

moving about on land as it does swimming underwater.

All four feet have five claws apiece and are webbed, but the

webbing of the front feet extends in a flat flange beyond the

toes when the platypus swims. Back on land or in its burrow,

the animal folds the extra webbing under its forefeet and walks

on its knuckles. The platypus uses the forelimbs and forefeet

for swimming and digging, while using the hind feet and claws

as combs to keep the fur clean and waterproof.

The eyes are small and the external ears are mere holes in

the skull, although the internal structure of the ears is like that

of other mammals. There are two long grooves for protecting

the eyes and ears, a single groove surrounding both the eye

and ear on each side. These grooves are closed underwater,

shutting both eyes and ears, when the platypus dives to hunt

for food. Out of water, the senses of sight and hearing

are sharp.

Both hind limbs of the male bear hollow, pointed, poison spurs

mounted on the insides of the ankles, just above the heels. There

are venom glands, one in each thigh, called the “crural glands”

because they are controlled by the crural nerves, which are ma-

jor motor nerves of the hindlimbs. The glands secrete venom that

is passed through ducts to the sharp spurs, which the platypus

can erect like jacknife blades and stab into other animals.

Both sexes have the spurs when they are young. At four

months of age, male spurs are protected by a covering of

whitish, chalky material that sloughs off completely by the end

of the first year of age. Females bear smaller, useless spurs,

without venom, that they shed by ten months of age.

The platypus’s flat, beaverlike tail is used as a swimming rud-

der, a shovel, for fat storage, and by the mother for keeping

eggs and young warm. The tail can store up to fifty percent of

a platypus’s total load of body fat. Female platypus use the tail

to carry leaves to the nesting chamber, and both sexes use it to

sweep loosened soil out of the way when digging. The tail has

no fine fur, only coarse, bristly hair on its upper surface to aid

in carrying or sweeping.

GEOGRAPHIC RANGE

Platypus are found only in mainland Australia and the south-

ern island of Tasmania. Platypus are distributed along Australia’s

east coast, to about 500 miles (800 kilometers) inland, from Cook-

town, Queensland to Melbourne, Victoria, and into Tasmania.

HABITAT

All platypus live on the edges of freshwater bodies like lakes,

ponds, rivers, and streams, in tropical and temperate regions.

DIET

The platypus eats small freshwater animals, which it hunts

at night, underwater, with its eyes and ears closed. It finds and

catches underwater creatures that are swimming or sunken in

the bottom mud by tracking them down with its sensitive bill,

which can detect electricity and motion.

Diet is varied, including adult and larval water insects, cray-

fish (called “yabbies” in Australia), fish, frogs, tadpoles, snails,

spiders, freshwater mussels, worms, fish eggs, and unlucky in-

sects that fall into the water from overhanging trees. Occasion-

ally, platypus probe for food at the edge of the water, grubbing

under rocks or among roots of plants. A platypus must eat one

third to one half of its body weight in food every day.

BEHAVIOR AND REPRODUCTION

Platypus are either solitary, or a male and female may live to-

gether, sharing a burrow. Platypus build two types of burrows

along the banks of creeks and ponds. One is a “camping bur-

rows,” an all-purpose shelter for male and female; the other is the

“nesting burrow,” built only by the female, and containing a

breeding chamber, or room, for birthing and raising the young.

Both sorts of burrows keep their entrances at, slightly above, or

below water level, the entrance tunnel climbing at an angle a few

feet above water level to prevent flooding of the burrow. The

openings can be difficult to spot, since platypus prefer to build

them as hidden as possible in sturdy, concave banks with reeds

and other aquatic plants at the water’s edge, and overhanging sod

and tree roots.

A burrow’s entrance tunnel is barely wide enough to allow

the platypus to pass, so that when the animal emerges from wa-

ter and forces itself through the entrance tunnel, water on the

pelt is squeezed and sponged off, and the platypus’s fur is dry

when it enters the main tunnel. A platypus may have up to a

dozen camping burrows strung along the banks of its territory,

providing numerous nearby, safe havens. The animal rotates

the burrows for shelter, staying at each a few days, probably to

keep down its population of parasites.

A nesting burrow can be as long as 90 feet (30 meters), with

two or more branching tunnels that circle about and eventu-

ally lead to the central nesting chamber.

Platypus normally hunt and feed at night, but have been seen

doing so in the daytime. In the water, a platypus propels itself

with powerful strokes of its forelimbs, the extended webbing

adding extra push to the motions. It uses the hindlimbs and

tail only for steering. As it swims, the platypus swings its head

from side to side, allowing a full scan of its surroundings with

its sensitive bill. The platypus feeds by snagging swimming

creatures with its bill and by rousting them out of stream bot-

tom mud and gravel, shoveling it up with its bill to put buried

creatures to flight, then catching them as they try to escape.

Since the platypus must breathe air, it combines underwater

hunting with trips to the surface to exhale and inhale. It will

usually stay submerged for about a minute at a time, although

it can stay submerged for up to five minutes. Platypus blood is

especially rich in red cells and hemoglobin, the substance in

blood that carries oxygen. The platypus can also ration its blood

oxygen supply by reducing its heartbeat from two hundred

beats per minute to ten beats per minute.

When not out hunting, a platypus rests in its burrow for up

to seventeen hours a day. Platypus are active throughout the

year, even in cooler southern Australia and Tasmania, where

water temperature drops nearly to the freezing point. Individ-

uals have been known to go into periods of torpor, or slug-

gishness and reduced activity with a lowering of body

temperature, during the coldest months. Such a period, which

can last up to six days, is not true hibernation but allows the

animal to conserve energy in cold times.

Platypus are for the most part silent. Some naturalists have

heard threatened platypus make soft, growling sounds that are

only audible at close range. Lifespans for platypus in captivity

and in the wild can reach sixteen years.

Platypus mate from August to October. Following an elabo-

rate courtship ritual that includes the male holding on to the

female’s tail, and the pair swimming in slow circles, the two cop-

ulate in the water. Then the female tends to the nesting burrow

and chamber, carrying wet leaves and moss with her folded tail

for lining the chamber, to prevent the eggs from drying out. The

female lays one to three eggs in the chamber two to four weeks

after mating. A typical egg is slightly oval, about half an inch

in diameter (13 millimeters), with a soft, leathery shell like a

reptile’s.

The mother incubates the eggs by holding them against her

belly fur with her tail, maintaining a constant temperature of

90°F (31.5°C). The young hatch in about ten days, each tear-

ing through the eggshell with a temporary egg tooth. The newly

hatched, inch-long young are fragile and translucent, blind and

furless, and at about the same stage of development as a newly

born marsupial young.

The mother, having no nipples, nurses the young with milk

that comes directly from her belly skin. In about four months,

the young emerge for the first time from the burrow, each about

a foot long and with a full coat of fur.

Predators of platypus, other than humans, include birds of

prey such as hawks, eagles, and owls; Murray cod, a freshwa-

ter fish; and crocodiles. Carpet pythons, goanna lizards and

rakali, or Australian water-rats, prey on young platypus in bur-

rows. Carnivorous mammal species introduced by European

settlers, including foxes, dogs, and cats, prey on platypus, al-

though some of these predators are dealt painful ends by the

poison spurs of male platypus.

PLATYPUS AND PEOPLE

The platypus, almost as much as the kangaroo, has become

a national symbol of Australia and of the odd, weird, and

outright bizarre creatures native to that continent and country.

The platypus is a symbol, as well, for the unique, the quirky,

and the unexpected in nature, which makes the animal and its

behavior a subject of curiosity and science education.

Platypus were nearly wiped out by hunting, into the early

twentieth century, for their fine, soft, waterproof fur. Never-

theless, humans, out of carelessness and ignorance, continue

to make life miserable for the platypus. The animals become

entangled in fishing hooks and lines, and in fishing nets; such

encounters end in drowning or in the scarring of the bill. Tas-

mania’s platypuses are being impacted by infection from an in-

troduced fungus and by chemical pollutants.

Well-meaning people may try to rescue a platypus that is

wandering and seems to be lost, a move that often proves harm-

ful to people and platypus. A wild platypus captured by hu-

mans will probably die of shock. The rescuers may end up with

days of pain and misery from a platypus sting. Wildlife educa-

tion in Australia stresses leaving lost animals alone and calling

a local office of the Australian Government Department of the

Environment and Heritage so that someone can professionally

capture and care for a lost platypus.

Recently, platypus have started invading human-made urban

waterways in Melbourne, Victoria, while disappearing from

some wild areas, for reasons still not understood. The urban

platypus most likely have been forced into artificial waterways

due to destruction of their habitat by development, and there

is enough live platypus food in the waterways to feed a platy-

pus population. The Australian Platypus Conservancy and the

Melbourne Water Department together have surveyed and

taken counts of the urban platypus populations. They found

that platypus in the waterways were as healthy and well-fed as

those in the wild, while some individual platypus from the wa-

terways have migrated and re-colonized river banks with im-

proved habitat.

CONSERVATION STATUS

Platypus are considered “common but vulnerable” by the

government of Australia. It is plentiful in some areas, but is

considered vulnerable due to habitat destruction from dams, ir-

rigation projects, being caught in fish nets and lines, and wa-

ter pollution.

Platypus are strictly protected by law and harsh penalties in

Australia, which is agreeable with most, if not all, Australians,

since the animals are not pests and are now national emblems.

The Australian government and private groups like the Aus-

tralian Platypus Conservancy keep close eyes on platypus pop-

ulations and have proposed relocating some of the urban

platypus to suitable natural areas where they have been driven

from by development in the past.