Odd, but the mammals are currently studied less well than the birds are. They are harder to observe than the birds are and the more intimate aspects of their lives are not known to science yet. For example, until recent times, the scientists did not know, though they argued a lot, about the pregnancy of a hare.
Many Europeans dismissed even the "foreign" platypus - whose existence even 150 years ago! - And it did not hide its' mysteries from the curious science. And the hare, who for a million years is running under the humans' very nose, was able to hide much of its' lifecycle.
First about the platypus. This is more logical. For this mammal is the most ancient one on Earth.
We do not know who caught the first platypus, but when and where it happened, is known precisely: Hawksbury, New South Wales, November of 1797. When the English naturalists saw the skin of the incredible creature, many of them decided that they are dealing with a fake. They decided that a skin of some tropical mammal got a duck's bill stitched on as a joke. Such tricks were often delivered from South Asia: a monkey would receive a fish's tail and be declared a mermaid and an iguana would get a cock's head - in Europe, such monsters were called the basilisks. Cabinets of curiosities were fashionable at that time and accumulated all sorts of things. "The scientists were inclined," Robert Knox, a famous anatomist from Edinburgh, wrote down a quarter of a century later, "to number this rare creation of nature into the same line with the Eastern `mermaids' and other fakes of such sort".
About a year passed before Dr. Show, a naturalist from the British museum risked examining the hide of the duckbilled monster. Having examined it attentively, he did not find any fakery: the skin was clearly made by nature and not by human hands. He named this wondrous creature the Platipus anatinus, which translated from Latin means: "the duckbilled flat-foot". The duckbill and its' `cousin' the echidna - simultaneously are both egg-laying and milk-feeding beasts. In this rare mix, we see the traits of that epoch, close to the modern world, when our distant ancestors already were covered in fur and began to feed their young with milk, but did not lose some traits of their ancestors - the reptiles, and in the spirit of tradition continued to lay eggs.
Before laying eggs, the duckbill female digs a burrow from 5 to 20 m in length. It digs close to water, but the entrance is not made underwater, as it is often written, but above it. At the end of the burrow, she makes a nest from wet leaves - specifically wet so that the nest would be sufficiently moist and the eggshell would not dry out - and also from grass, reeds and tree branches, which she breaks and handles for a long time with her toothless jaws. Grabbing them all with her tail, and not her beak, she puts it into her burrow.
Then, also using her tail as a stonemason uses his trowel; the female platypus builds a thick wall from earth and mud, which, as a barrier, separates the nest chamber from the other chambers of the burrow. She makes it so to keep in the nest chamber the right temperature and moisture. The female, sealed in her self-made thermohydrostate is harder to be found by enemies too. Her enemies are few in number, but they do exist: a small python, a local monitor lizard, and foxes that were brought from Europe.
Having used a clay world to part herself from the world, the female platypus lays two opaque-white eggs into the nest chamber.
They are soft: the shell folds under fingers. Rolling herself into a knot, the mother presses her potential offspring to her chest and warms them with her body heat. Therefore, not just with the bill does the platypus resemble a bird: like a bird, she incubates her eggs!
Possibly the warmth of the rotting vegetation, from which the nest chamber is made, also warms them. However, Dr. Croombiggle says that that is very unlikely. First, the leaf layer is too thin for that, and second, the platypus kits hatch from their eggs very quickly: the leaves do not have time to rot. After 10 - 14 days, and in some cases after 7 - 10 days, cutting through the eggshell with the egg tooth, the young beaked mammals emerge into the world. The egg tooth - it is located on top of the upper beak - it is a "can opener" in a sense that nature has awarded with many youngsters that hatch from shelled eggs: bird hatchlings, newborn reptiles, echidnas and duckbills. Its' only designation is to open the shell before hatching. Having down this simple job, the egg tooth falls off.
In addition, the young duckbills long after the egg tooth is gone - for 9, 11, or even 17 weeks - lie blind and helpless on the leaf mattress. All that time their mother feeds them with milk. She has no nipples; therefore, the pups lick it straight from the skin. The female lies belly up, her milk from the milk glands drips into a small grove on the belly.
From there the pups lick it themselves, until they grow up and learn to hunt and eat worms, snails and crayfish.