The duck-billed platypus is the most evolutionary distinct mammal alive today and a member of the most primitive order of mammals on Earth, Monotremata. They are the only surviving member of the family Ornithorhynchidae, which dates back to the Cretaceous period 146 to 165 million years ago; the other members became extinct 34 to 35 million years ago during the Oligocene and Miocene periods. Truly one of nature's oddities, the conservation of the duck-billed platypus is extremely important because of its evolutionary distinctiveness.
Duck-billed platypuses, with their combination of seemingly mismatched physical characteristics, are perfectly adapted to their semi-aquatic life in the freshwater habitats of eastern Australia, New Guinea and Tasmania. They do not have external ears like most exclusively land-dwelling mammals, they walk like reptiles, they have streamlined bodies like otters, broad tails like beavers, bills that are shaped like a duck's bill and duck-like webbed feet -- and most unusually for a mammal they lay eggs covered in a shell that hatch outside the body. Like reptiles, they have only one posterior orifice for both excretion and reproduction; both the anal and urinogenital apertures open into a common chamber at the end of the gut called a cloaca. Platypus adults have no functional teeth. Adult males are about 2 feet long, including the six-inch tail, and females are smaller. Adults weigh from 1 to about 4 pounds. Platypuses' long, leathery bills are perhaps their most distinctive physical feature, and their most important tool for hunting. Electro-receptors in the elongated protuberance allow them to detect the electric fields of the bottom-dwelling invertebrates they eat, and unlike a duck's bill, a platypus' highly sensitive bill is not hard, but soft and moist.
Diet, Adaptation and Behavior
Dependent upon permanent freshwater for their survival, duck-billed platypuses swim and dive mostly in the early mornings and late evenings, leaving their burrows to probe the mud and gravel river and stream beds in search of crayfish, shrimp, insect larvae, snails, tadpoles, worms, small fish and other freshwater invertebrates, their electro-charged bills allowing them to successfully hunt in the murkiest water without actually seeing their prey. Well-equipped for an amphibious life, their five-toed webbed feet and wide, flattened tails help propel them through the water. Their head, trunk and tail are completely covered in a double coat of soft, dense, brown fur that provides insulation and buoyancy in the water. Males have hollow, horny spurs on their heels that secrete venom, useful during the breeding season when they fight with other males over access to females.
Reproduction and Ecology
Females begin breeding at 2 to 3 years old and lay about two eggs at a time. During the breeding season, the male platypus maintains the burrow for both sexes. When the female is ready to lay eggs she constructs a different type of burrow where the eggs are incubated and hatch. Born naked and blind, the tiny young remain in the burrow for about four months, during which time they're nourished by milk produced by the mother and delivered through numerous teatless mammary glands that are small openings in her underbelly. The average lifespan of a platypus in the wild is about 13 years. .
Habitat and Distribution
Platypuses construct burrows in the banks of freshwater streams, lakes and lagoons throughout eastern Australia in New South Wales and Queensland, south-eastern South Australia, Tasmania and Victoria. Recently a population was introduced to two streams, Rocky River and Breakneck River, on Kangaroo Island off the coast of South Australia and is thriving without any adverse affects to the native wildlife.
Hunted for their fur until the early 20th century, platypuses have recovered well primarily due to government conservation programs in the states in which they occur. Improved fishing regulations since 1950 include a larger mesh size for fishing nets, with a particular focus on New South Wales where the impact from fishing gear has the most impact on platypus populations. Though less than in earlier years, accidental entanglement in fishing nets still results in some mortality. Habitat disruption from dams, irrigation projects and pollution may pose a threat for the future, but platypuses, classified as "Least Concern" in the 2007 IUCN Red List of Threatened Species, still continue to thrive in these less than perfect environments with the present distribution little altered from pre-European times. Other threats include poachers who use illegal nets and some fragmentation of their distribution is attributed to poor land management practices that lead to stream bank erosion, sedimentation of the freshwater habitat and vegetation loss in those areas in close proximity to water courses.