Photo: Platypus face and beak
The platypus is a small semi-aquatic Australian mammal with a duck-like beak, a beaver-like tail, and otter-like webbed feet with venomous spurs. It is a monotreme, one of only two animals that lays eggs like a bird—but feeds its babies milk like a mammal. For these reasons, when Europeans first saw this odd animal in 1798, they were convinced the platypus was a hoax—a humbug!
The platypus is also called a duck-billed platypus. The platypus's scientific name is Ornithorhynchus anatinus. Officially, a baby platypus is called a "baby platypus". However, it is sometimes called a puggle, but there is some debate about this usage.
Photo: Platypus face and beak
The platypus is 35-50cm (14-20in) long, weighs 0.5-3kg (1-6.5lb), and is roughly the size of a cat. It has double-layered waterproof fur brown on its upper body and light grey or cream on its under-body. The platypus's front feet are fully webbed, while its back feet only have partial webbing. It can retract the webbing on its feet, allowing it to navigate water and walk on land. Its broad flat tail acts as a stabiliser while swimming and stores fat reserves to draw on during hard times.
The most prominent feather of the platypus's flat head is its huge, flat, black, rubbery beak - called a bill. This bill has thousands of sensitive electro-receptors that act like sonar, allowing the platypus to detect underwater obstacles and locate its prey. At the front of its bill are two nostrils that remain open while above water but close underwater to keep water out. Directly behind the bill are two grooves with eyes and ears that open and close like a pair of eyelids. In addition, the platypus has a third inner eyelid called a nictitating membrane – like in cats, birds, and crocodiles - that works as an internal squeegee, wiping away dust and debris from the eye.
The platypus is a monotreme and has a single opening at the end of its body called a cloaca, into which its intestinal, genital, and urinary tracts connect. In most other mammals, there are two openings, the rectum/anus and reproductive tracts, such as the vagina and penis.
Photo: Venomous spur on male platypus's hind leg
The male platypus produces venom, which it can inject into its victims through a sharp spike-like spur on each of its hind limbs. Contrary to popular belief, the platypus is not poisonous (see explanation below).
Platypus venom is composed mainly of defensin-like peptides (OvDLPs) unique to the platypus. Swelling develops around the puncture wound and gradually spreads outward. While not fatal to humans, its venom can cause excruciating and prolonged pain strong enough to incapacitate its victim. Even powerful painkillers cannot suppress the pain, and no antivenom is available. Smaller animals, such as dogs, can die from platypus attacks.
The platypus attacks by clamping its hind legs around its victim and repeatedly jabbing its venom-injecting spurs. It may also cling tenaciously to its victim. The platypus is not aggressive and will only attack if provoked or during mating season when duelling with another male platypus when competing for females.
A venomous animal injects or otherwise delivers its toxin into another animal. By contrast, a poisonous animal's entire body or parts of it may contain a harmful toxic substance if touched or eaten. Because the platypus injects its toxins, it is venomous–not poisonous.
Photo: Platypus habitat map
Platypus live in creeks, streams, billabongs, and ponds in eastern Australia, where the climate is temperate to sub-tropical. They prefer heavily wooded areas with steep and stable riverbanks into which they can dig their burrows. They also require waterways with gravelly or pebbled streambeds where their food sources are found.
A platypus establishes a home range and forages in that range. Its home range may overlap with other platypuses, but they do not have territorial disputes. Instead, they try to avoid each other, even changing their foraging schedule to do so.
Photo: Platypus home burrow on a riverbank
Platypuses build two types of burrows. Nesting burrows, constructed by females built deep into the riverbank, have an entrance point up to 4 meters away from the inner nesting chamber. On the other hand, camping burrows, built by both male and female platypuses, consist of a short tunnel of 1 to 2 meters leading to a dry nestling chamber. A platypus may have multiple camping burrows dispersed throughout its home range.
Photo: Platypus foraging for food underwater
Platypuses eat aquatic invertebrates such as water beetles, snails, shrimp, mussels, worms, mayflies, black flies, and crayfish. Occasionally they also eat small frogs and fish. They forage for food mainly at night or in the evening.
The platypus hunts by moving its head from side to side as it swims underwater and picks up the tell-tale electrical signals given off by its prey. Then, quickly homing in on these signals, the platypus shovels them out of the stream-bed with its bill and pounces on them. It stores its catch temporarily in cheek pouches located just behind its jaw. Then, it continues to search for more prey. In 30 to 60 seconds, when its oxygen supply starts to run out, the platypus heads back up to the surface. Once on the surface, the platypus retrieves the morsels stored in its cheek pouches, grinds its food between two bony plates on their upper and lower jaws, and swallows the mashed-up food. The platypus spends 10-12 hours a day foraging for food and consumes 15-30% of its body mass in food each day.
The platypus does not have a stomach. Instead, it has a sac between its oesophagus and intestine that secretes powerful digestive acids and enzymes to break down its food. Scientists believe the platypus lost its stomach because its diet does not require a complex organ, such as a stomach, to break down its food.
Photo: Platypus egg in mother's pouch
During the mating season between June and October, a male platypus has only one aim: to win territory and secure any females within it. To do this, the male produces venom in its rear spurs and battles other males for the female's affection. These fights are rarely fatal; the toxins usually paralyse the loser until it retreats. The victor wins whatever females reside in his newly won territory. Females do not appear to be picky about the male they couple up with. They mate with any male in their territory, assuming he is probably the biggest and strongest in the area. The courting ritual lasts for several weeks, during which time the female plays coy and refuses his advances until she is receptive. She will indicate her readiness to mate by nipping the male on his tail. He will nip hers in return, and they will swim in a circle and indulge in other aquatic courting rituals for a few days more before mating. Copulation occurs when the male partially mounts the female, inserts his four-pronged penis in her cloaca and ejaculates into her. This process takes around 10 minutes. Once copulation is complete, the male departs to find another female, and the female starts preparing her nesting burrow.
Photo: Platypus baby puggle in mother's pouch
The female lays one to three leathery white eggs, the size of small marbles (11 mm), about 2-3 weeks after mating. She positions these eggs in a slight depression on her belly and curls up its tail to cradle them. Kept warm by her, the eggs incubate for about ten days. About 9 mm in length, the young platypus hatchling breaks out of its egg by tearing the shell open with a small egg tooth on the tip of its snout and clawing its way out with its front feet.
Once the hatchlings are born, the mother's body secretes milk from two special paths on its skin (as the platypus does not have nipples like other mammals). Because its milk is deposited on the surface of the skin and doesn't offer the relative sterility of a nipple, its milk contains special antimicrobial chemicals which protect young from infection.
Photo: Platypus babies - puggles
Baby platypuses (sometimes called puggles) remain in the burrow for about 3-4 months feeding on milk and then on solids brought to them by their mother. When they finally emerge, they are about 80% of the length of an adult platypus and are fully furred. At this time, they need to fend for themselves, learning to swim and feed on their own. Platypuses reach sexual maturity at two years of age. The platypus has a lifespan of up to 17 years.
Video: Platypus walking
On land, the platypus walks in a style similar to reptiles such as crocodiles or lizards. Its legs move from the side of its body rather than from under it. Furthermore, the platypus walks on its knuckles to prevent its webbed feet from getting entangled in vegetation. (Gorillas and chimpanzees also use knuckle-walking). Because a platypus is built for efficiency in water, it is not well adapted for walking on land. As a result, they rarely walk on dry land.
Video: Platypus swimming
The platypus is an expert swimmer and diver. It swims and propels itself underwater using its large webbed paddle-like front feet and steers with its tail and rear feet. It closes its eyes, nostrils, and ears when swimming underwater and uses its super-sensitive bill to guide it through the water. A Platypus usually remains submerged for about 4 minutes but can remain submerged for as long as 14 minutes. It can swim and dive at the rate of 12 meters per minute. While foraging for food, it travels at a speed of about half a meter per second. The platypus has a very low above-water profile making it hard to spot.
Platypuses fall prey to dingoes, feral cats, foxes, large birds of prey and crocodiles. Domestic dogs, too, occasionally attack platypuses. Water-rats and goannas threaten the young platypuses in nesting burrows. Humans and climate change, however, pose the most significant risk to the survival of the platypus.
The platypus is listed as 'Near Threatened' on the IUCN Red List of Threatened Species. This means it risks becoming threatened if appropriate conservation measures aren't taken. Reasons for its decline include habitat loss and degradation, pollution, climate change, and predation from introduced species such as foxes. Conservation efforts for the platypus include monitoring and research for a better understanding of their populations and ecology, protecting and restoring their habitats, controlling the impacts of introduced species, and raising public awareness.