When the first platypus pelt arrived at London's
Natural History Museum in the late
1790's, it was thought to be a fake made from bits
of animals sewn together. This unusual mammal
has a leathery bill, webbed feet, and fur, and it is
one of only three mammals that lay eggs. Its body
length is about eighteen inches, and its broad, flat
tail is about seven inches long. The reclusive
platypus spends most of its time in streams,
rivers, and some lakes, foraging for food in the
evening and sleeping during the day in burrows
dug into the river banks.
The unusual anatomical features of the platypus provide perfect adaptations for its life in water. The webbed feet are efficient paddles for swimming through the water. Claws on the feet help the platypus to dig burrows. Dense, waterproof fur covers the entire body except the feet and bill. The eyes and ear holes of the animal lie in folds that close when the animal is submerged, and the nostrils are located toward the end of the beak and also close under water. The bill is highly sensitive to touch, and is equipped with electrosensors that detect weak electrical fields produced by prey. Thus, the platypus can locate and capture prey in murky river bottoms without relying on vision, hearing, or smell. Bottom-dwelling invertebrates, especially crustaceans, aquatic insects, and insect larvae, compose the majority of the platypus diet. Behind the bill are located two internal cheek pouches containing horny ridges that substitute for teeth, which are lost early in the life of the platypus. The pouches are used to store food while it is being chewed and sorted by the animal. Amale platypus has a spur on each rear ankle that is connected to a venom gland in the thigh. The spur is used against attackers, but also against competing males during the mating season. The venom is not fatal to humans, but can cause a great deal of pain. This feature makes the platypus one of very few mammals that are venomous.
From Egg to Adult
Courtship and mating occur in the water. After initial approaches by the female, the male chases and grasps her by the tail and inseminates her. After mating, a female will lay two to three eggs and incubate them in a special nesting burrow, which may extend one hundred feet away from the water. The female blocks the entry to the nesting burrow with soil plugs to protect the eggs and young from predators and flooding. She removes and replaces the plug each time she leaves to forage for food. When the eggs hatch, in seven to fourteen days, the young are about one inch long and totally dependent on the mother. Platypuses do not have nipples, but milk is produced in themammaryglands and expressed through openings in the abdominal wall. The young suck the milk directly from the fur. At about five months of age, the young emerge from the nesting burrow and begin learning to search for prey themselves. A typical platypus in the wild will live about ten years.
Genus and species: Ornithorhynchus anatinus
Geographical location: Eastern Australia, Tasmania, Kangaroo Island in southern Australia
Habitat: Streams, rivers, and some lakes; must have permanent water and banks suitable for burrows
Gestational period: Seven to fourteen days
Life span: Ten or more years in the wild; seventeen years and longer in captivity
Special anatomy: Rubbery beak equipped with electrosensors used to detect prey; webbed feet; females have slits in abdominal walls from which milk expresses during lactation; males have spurs on rear feet used primarily to inject venom into rivals during mating season; reproductive and excretory tracts have one common opening to the exterior of the body
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