Swimming into the steady current on the surface of a shallow, rippling tributary in the Australian province of New South Wales, an elongated creature with dense brown fur moves through the water with ease. With its hind feet tucked into its body, the animal gains all forward momentum by alternately paddling its front pair of broad, webbed appendages. Although aquatically adept, the lone individual looks suddenly clumsy upon reaching a nearby riverbank, walking with a reptilian gait. Fur still slick from the early morning swim, the duck-billed creature clambers up the steep, muddy slope, its long tail skillfully curled to hold a cluster of leaves, twigs, and reeds like an additional limb.
Just a few feet above water level, the odd-looking specimen disappears into a small hole mostly obscured by surrounding brush. With a flat and slim physical frame, wiggling through the narrow tunnel is manageable enough. For weeks, this female tirelessly burrowed into this slope, implementing every safety precaution along the way; she navigates the dark passageway by memory, remembering every point along the path blocked by plugs protecting the shelter from potential floods or predators. After traveling nearly 20 meters (66 feet) the tunnel finally ends, expanding into a more spacious cavity. Her adventure complete, the female unfurls her beaver-like tail to deposit and arrange the collected foliage, careful not to disturb the pair of tiny leathery eggs nested at the far end of the den.
In stark contrast to nearly every other species of mammal on Earth, the Platypus represents one of the five extant monotremes: mammals that lay eggs. Like any mammal, fertilized eggs initially develop in utero. After twenty-eight days, however, where most mammal mothers would undergo a live birthing, Platypus mothers lay their eggs. After ten days of external incubation in an underground burrow, these eggs will hatch, yielding hairless and blind babies.
It is no wonder that when Europeans first laid eyes on this odd species in 1798 they believed it to be some sort of practical joke. Robert Knox posited that an Asian taxidermist had somehow sewn a duck's beak onto the body of an Australian beaver. George Shaw went as far as to take a pair of scissors to the creature's face to check for stitches. Needless to say, no amount of prodding or examining ever revealed any evidence of bizarre breeding or twisted taxonomy. The Platypus was as true a product of nature as it was eclectically unique.
Endemic to streams and rivers in numerous climate zones in eastern and southern Australia and Tasmania, Platypus prefer shallow waters, never deeper than 5 meters (16.4 feet). Thriving in a diverse range of habitats, from tropical rainforests on the coasts of Queensland to the colder altitudes of the Australian Alps in New South Wales, Platypus have adapted well. Most notably, whereas most placental mammals are endothermic with body temperatures at 37 degrees Celsius (99 Fahrenheit), these monotremes live at only 32 Celsius (90 Fahrenheit).
Active during evenings and early mornings, they devote most waking hours to scouring the riverbeds for food, consuming approximately 20% of their own body weight in annelid worms, insect larvae, and freshwater shrimps and crayfish every day. Diving for thirty-second stints, Platypus seal their eyes, ears, and nose shut while submerged underwater. Thanks to a unique evolutionary adaptation, the absence of sights, sounds, and smells does not impede acute hunting skills.
While electroreception - the ability to sense electrical impulses - is commonly found in numerous species of fish, monotremes almost exclusively possess this capacity among mammals. In Platypus, these powerfully sensitive receptors are found throughout the rubbery duckbill, which subsequently governs the somatotopic map of the species' brain in the same way that hands dominate the cortical homunculus in human brains.
Darting through the water, the Platypus tosses its head repeatedly from side to side, allowing the hunter to gauge the direction of its targeted prey through an instinctive process of comparing the differences in signal strength across a sheet of electroreceptors. Even the slightest muscle contraction of a worm will create an electric field that can be easily detected by the highly attuned duckbill. For prey dwelling beneath sunken stones and soil, the duckbill serves a dual purpose as a shovel. Without slowing its paddle, the Platypus digs into the sediment for food, storing it in cheek pouches to be consumed shortly after at the surface.
While its diet is entirely comprised of small invertebrates - manageable morsels of food incapable of resistance - the Platypus is hardly at the top of the southeast Australian food chain. Snakes and crocodiles prowl the waters, foxes survey the shores, and numerous eagles, hawks, and owls soar through the skies all looking for food. Measuring no longer than 50 centimeters (20 inches) and weighing an average of 1.5 kilograms (3.3 pounds), Platypus make for a decently hearty meal. Smooth, wet fur provides an element of camouflage among similarly dark stream stones, but Platypus paddling about on the surface remain relatively easy to spot.
Fortunately, they are not completely helpless. Usually concealed against their back limb, adult male Platypus wield a venomous spur loaded with more than twenty poisonous peptides capable of inducing lowered blood pressure, increased blood flow around the wound, and intense pain. While this toxic attribute serves as their principle line of defense, males will more often employ their spurs as an offensive weapon to assert dominance in territorial and mating disputes. Considering Platypus poison lacks a lethal punch, these fights do not result in any deaths and only serve to impress potential mates.
When a male has selected a female to pursue, he will grab on to her tail with his bill. If she is unwilling to mate, the female will send the male on a ride of rejection, frantically swimming near logs and stones in an attempt to escape. If she reciprocates, the female will allow the male to bite her tail again. Soon after copulation, the male will return to his solitary life, leaving his mate to construct the burrowed nest and care for the offspring on her own.
A male Platypus swimming in a stream, just outside a female's terrestrial burrow, in the southeast of Australia. On the surface its eyes and nostrils are wide open, though when submerged they are closed. Small fish, in what is referred to as the Galaxias-species complex are shown swimming in the foreground. The aquatic larva of a caddisfly appears upon a piece of wood at the lower left of the painting. Even if hidden amidst the fallen leaves at the bottom of the stream, it could be detected by the Platypus. One of the Platypus' pair of poisonous spurs is visible on the animal's left rear foot. Ferns and tree ferns are visible in the distance on the banks of the stream and a water plant in the genus Vallisneria appears below the animal.