There is no shortage of unusual observations in the world of animals, with many diverse species employing unique and unexpected traits and behaviors in order to survive in their natural habitats. However, in the world of exotic animals, few can compete with the natural aberrancy of the platypus. This charming little mammal possesses a duck-like bill, webbed feet, a tail similar to that of a beaver’s, the body and fur of an otter, lays eggs while still feeding its young with milk, and, in the case of the male of the species, also has venomous stingers on the heels of its rear feet. It is, therefore, no surprise that when scientists first examined a specimen, they concluded that it must have been a hoax since an animal such as this could not possibly be real. However, it soon became clear that the platypus was indeed quite real, and since then it has become an icon of peculiarity, a wonder to all who observe it, be it children or scientists. Put simply, the platypus is a strange and unlikely animal. However, it also well equipped to survive in the wild and is among the last remaining members of an ancient lineage of mammals dating back to the age of the dinosaurs. In this sense, one can find beauty in the successful design of the platypus.

The platypus (Ornithorhyncus anatinus) is a rather small mammal, averaging out at a total length of 20 inches and a weight of about 3 lbs,[1] with males being larger than females and different environments causing noticeable size variations.[2] The presence of the duck-like bill immediately distinguishes the platypus from any other mammal. The bill, however, is not designed like that of a duck’s; it is soft, rubbery, and contains a large number of nerve receptors which respond to electrical and tactile stimuli, allowing the platypus to search for prey and move its way around when submerged. The upper part of the bill is of a blue-grey coloration, while the smaller underside is a pale pink or mottled color. The nostrils are located just behind the tip of the bill, making it possible for the animal to breathe while keeping most of its body submerged, much like a crocodilian. A frontal shield is present at the back of the bill, though its purpose is currently unknown. The body of the platypus is flat and streamlined, with short limbs. Save for its bill and feet, the body is covered with waterproof hair. The long and coarse outer hair is dark brown on the animal’s back and of a more yellow color on its underside. Below this outer hair is a fine, dense fur which has a similar feel to wool and ranges from grey to dark brown .The forefeet are webbed while the hind feet are only partially webbed. As a result, the platypus swims by alternatively kicking its forelegs in order to propel itself through the water while relying on its hind legs as steering rudders. The tail is mainly composed of fatty tissue which stores energy for the platypus during food shortages, such as in the winter months. The top of this tail is covered in hair while the bottom exhibits only sparse hair growth. To many, the tail of the platypus is similar to that of the beaver’s. However, it is designed differently and has a different purpose. The tail of the beaver is flatter, broader, and covered in special scales which are used to help it propel itself underwater. The platypus, on the other hand, uses its tail for steering along with its hind legs. When moving about on land, the platypus walks in a reptilian waddle since its legs extend out from the sides of the body. During this time, the webbing is folded under the animal’s feet, thus avoiding any damage from occurring as the platypus awkwardly waddles throughout its habitat. When the webbing is folded, the platypus’ broad nails, which are used for digging, are uncovered. One of the odd adaptations observed in the biology of the platypus are the long spurs present in the male’s hind ankles. The spurs are hollow and linked to venom glands in each thigh by a duct.[3] It has been suggested that these spurs are used in fights between males during the mating season.[4] While juvenile females possess rudimentary versions of the spurs, these are lost within their first year.[5] Platypuses are born with milk teeth, but these are soon lost; as adults they rely on special plates in their bills for grinding their food.[6]

The platypus is one of the few living monotremes, members of the order Monotremata, with the short-beaked echidna (Tachyglossus aculeatus) and the long-beaked echidna (Zaglossus bruijnii) being the only other extant representatives of the group. The monotremes are a rather interesting and ancient group of mammals which have several characteristics in common with reptiles. The group’s name stems from the fact that monotremes use the same opening for reproduction and eliminating waste products. This opening is called the cloaca, and is also present in reptiles and birds. Other reptilian characteristics observed in monotremes include the ability to lay eggs, the presence of cervical ribs, and the localization of ascorbic acid composition in the kidney.[7] Due to this collection of reptilian features, some scientific authorities once considered the group to be an unusual lineage of reptiles.[8] Unlike all living reptiles, and like all other mammals, monotremes are endothermic, or “warm-blooded,” meaning they generate their own heat to regulate their body temperature regardless of the ambient temperature. However, monotremes have unusually low metabolic rates and maintain a body temperature lower than that of most other mammals.[9]

The platypus is found only in Australia, specifically in New South Wales, Queensland, south eastern South Australia, Tasmania, and Victoria. There is also an introduced population present on Kangaroo Island off the coast of South Australia. The species occurs in freshwater streams, lakes, and lagoons. The platypus is common throughout much of its range with the exception of South Australia, though its abundance is not easily measured and therefore there are no population estimates. Nonetheless, the platypus is not considered endangered.[10]

These animals forage for food about 12 hours every day and are capable of consuming 13-28% of their body weight in food a day. When foraging, they dive for 20-40 seconds, usually in shallow water less than five meters deep. After acquiring prey, platypuses return to the surface in order to rest briefly, chewing for only about 10 seconds until they dive again.[11] During these dives, folds of skin cover their eyes and ears to prevent water from entering, and their nostrils close with a watertight seal. They then begin using their special sensitive bills to search for prey along the bottom.[12] Their diet mainly consists of small invertebrates such as crustaceans, worms, mollusks, and the larvae of many freshwater insects. Once these small animals are caught, they are stored in cheek pouches and carried to the water’s surface, where the platypuses make us of the grinding plates in their bills in order to break down their food. On some occasions, platypuses will also wander onto land in search of food, sometimes venturing surprising distances and reaching other bodies of water in the process.[13] However, most remain foraging in the water, where they play an integral role in the aquatic food chain by foraging on invertebrates.[14]

Being a small mammal, the platypus is not without dangers of its own. It shares its habitat with a variety of predators which would not hesitate to attack an unwary platypus. These animals include foxes, dogs, snakes, birds of prey, feral cats, and large eels.[15] Crocodiles have also been known to suppress platypus populations along some areas in their northern distribution. Though the platypus’ venomous spur may not offer much protection against a 1000 lb crocodile, it can function rather well as a weapon against smaller animals, and has even been known to kill animals such as dogs, as well as other platypuses. In the past, humans hunted platypuses extensively for their pelts, a practice which almost drove the species to extinction. However, platypuses are now protected by law, and hunting by humans is no longer a threat to the species.[16]

Platypus males reach sexual maturity at the age of 1.5 years, while females do not reach sexual maturity until they are closer to two years of age, though many females do not breed until they are four years old. The platypus mating season lasts from autumn to late winter. Many details of platypus reproduction are not understood due to the shy, secretive nature of the species. Successful mating relies entirely on the willingness of female platypuses, even though it is the males which initiate most mating interactions. Male and female platypuses touch as they swim past each other, a behavior which eventually leads to the process of mating when the male eventually grabs the tail of the female using his bill. However, the female may not be willing to mate at that time, and if so she will respond by trying to escape, usually by swimming through logs and other obstacles until the male is forced to release her. If the female is willing to carry on with the process, then she will stay near the male and even allow him to grip her tail again should he accidentally lose hold of her. The male then curls his body around the female, moving his tail underneath her to one side of her tail. The male platypus then goes on to bite the hair on the female’s shoulder with his bill, locking the two into a better mating position. However, little is known about the mating process beyond this.[17]

Platypuses are among the few mammals to lay eggs, a characteristic which makes the monotreme order unique among mammals. The estimated gestation period lasts 27 days, and the female then usually lays two eggs which she incubates for a further ten days in a burrow by pressing them against her belly using her tail.[18] When the young hatch, they are blind, naked, and totally helpless. Since the female platypus lacks teats, milk is instead secreted from pores in the skin. The young then drink her milk as it accumulates in grooves present in her abdomen. This continues for about four months until the young are able to emerge from their burrow and switch to a different diet of aquatic invertebrates.[19]

As stated previously, the platypus was once hunted excessively for its fur, a practice which took place until the early 20^th century. The species was also subject to accident drowning due to nets used by inland fisheries until about 1950. The species has recovered rather well as a result of an effective government conservation program. However, that is not to say that the species is free from threats today; habitat disruption caused by dams, irrigation projects, and pollution are a danger to Australian freshwater systems. Furthermore, accidental bycatch in inland fishing gear still remains a threat to the species, as it results in a small but noticeable degree of mortality. Nonetheless, the species has continued to inhabit and reproduce in considerably degraded environments. Though the platypus is fairly common throughout the majority of its range, the population in South Australia has nearly been wiped out entirely; there are almost certainly no naturally occurring populations remaining in the state. Its distribution has also decreased in the lower areas of the Murray and Murrumbidgee River systems in Victoria and New South Wales. It is certainly possible that commercial and illegal fishing operations within the platypus distribution in these river systems have resulted in this suppression of population numbers. A study indicated that the legal fishing nets used in the industry are less of a threat to the species than those used by poachers. Another problem is the fact that the abundance of platypuses is difficult to measure, meaning the species future conservation status will not be easy to predict. Several studies reported fragmentation of platypus distribution within individual river systems, an occurrence which has been attributed to poor land management practices leading to stream bank erosion, sedimentation of water bodies and the loss of vegetation at areas adjacent to water courses. Other problems which may adversely affect the species in the future include river regulation, the introduction of foreign species into the ecosystem, poor water quality, and the effects of disease on platypus populations. These threats, however, have yet to be studied extensively.[20] For the time being, however, the platypus population is still going strong, and has come a long way since it was nearly hunted to extinction in the last century. Losing the platypus would indeed be a great shame, as there are no other animals like it.

Originally considered too weird to be a real animal and now renowned as one of nature’s most exotic creatures, the platypus has come a long way in the eyes of humans. This odd little mammal, one of the last living representatives of the ancient mammal order, Monotremata, exhibits an extraordinary collection of adaptations which have captured the intrigue of scientists since its discovery. Yet it nearly joined its ancient ancestors in extinction as the species was nearly wiped out due to overhunting. Fortunately, an effective conservation program allowed the species to rebound in population numbers and recover. Thus the platypus remains with us to this day, a shining example of one of nature’s great oddities, and an object of fascination to all who observe it.