Animals

If you were asked to think of the most unusual and the most ugly animal that you could think of what would come to mind. The first thing that comes to my mind is the duck-billed platypus. Not only is it incredibly ugly, but you can’t help but wonder what it’s purpose is. How much do we really know about this strange creature.

The Platypus (Ornithorhynchus anatinus) is a semi-aquatic mammal to eastern Australia and Tasmania. Together with the four species of echidna, it is one of the five species of monotremes, the only mammals that lay eggs instead of giving birth to live young. It is the sole living representative of its family and genus, though a number of related species have been found in the fossil record.

The bizarre appearance of this egg-laying, duck-billed mammal baffled naturalists when it was first discovered, with some considering it an elaborate fraud. It is one of the few venomous mammals; the male Platypus has a spur on the hind foot which delivers a poison capable of causing severe pain to humans. The unique features of the Platypus make it an important subject in the study of evolutionary biology and a recognizable and iconic symbol of Australia; it has appeared as a mascot at national events and is featured on the reverse of the Australian 20-cent coin.

Until the early 20th century it was hunted for its fur, but it is now protected throughout its range. Although captive breeding programs have had only limited success and the Platypus is vulnerable to the effects of pollution, it is not under any immediate threat. The body and the broad, flat tail of the Platypus are covered with dense brown fur that traps a layer of insulating air to keep the animal warm.

The Platypus uses its tail for storage of fat reserves, an adaptation it shares with the Tasmanian Devil. It has webbed feet and a large, rubbery snout; these are features that appear closer to those of a duck than to those of any known mammal. The webbing is more significant on the front feet and is folded back when walking on land.

Unlike a bird’s beak (in which both the upper and lower parts of the beak separate to reveal its mouth), the snout of the Platypus is a sensory organ with the mouth on the underside. The nostrils are located on the dorsal surface of the snout while the eyes and ears are located in a groove set just back from it; this groove is closed when swimming. Platypuses have been heard to emit a low growl when disturbed and a range of other vocalisations have been reported in captive specimens.

Weight varies considerably from 700 g (1.54 lb) to 2.4 kg (5.3 lb) with males being larger than females: males average 50 cm (20 in) total length while females average 43 cm (17 in). There is substantial variation in average size from one region to another, and this pattern does not seem to follow any particular climatic rule and may be due to other environmental factors such as predation and human encroachment.

The Platypus has an average body temperature of 31–32 °C (88–90 °F) rather than the 38 °C (100 °F) typical of placental mammals. Research suggests this has been a gradual adaptation to harsh environmental conditions on the part of the small number of surviving monotreme species rather than a historical characteristic of monotremes. Modern Platypus young have three-cusped molars, which they lose before or just after leaving the breeding burrow; adults have heavily keratinised pads in their place.

The Platypus jaw is constructed differently from that of other mammals, and the jaw opening muscle is different. As in all true mammals, the tiny bones that conduct sound in the middle ear are fully incorporated into the skull, rather than lying in the jaw as in cynodonts and other pre-mammalian synapsids. However, the external opening of the ear still lies at the base of the jaw.

The Platypus has extra bones in the shoulder girdle, including an interclavicle, which is not found in other mammals. It has a reptilian gait, with legs that are on the sides of the body, rather than underneath. The male Platypus has venomous ankle spurs which produce a cocktail of venom, composed largely of defensin-like proteins (DLPs), which is unique to the Platypus. Although powerful enough to kill smaller animals, the venom is not lethal to humans, but does produce excruciating pain; so intense that the victim may be incapacitated.

Oedema rapidly develops around the wound and gradually spreads throughout the affected limb. Information obtained from case histories and anecdotal evidence indicates that the pain develops into a long-lasting hyperalgesia that persists for days or even months. Venom is produced in the crural glands of the male, which are kidney-shaped alveolar glands connected by a thin-walled duct to a calcaneus spur on each hind limb.

The female Platypus, in common with echidnas, has rudimentary spur buds which do not develop (dropping off before the end of their first year) and lack functional crural glands. The venom appears to have a different function from those produced by non-mammalian species: its effects are non-life threatening but nevertheless powerful enough to seriously impair the victim. Since only males produce venom and production rises during the breeding season it is theorized that it is used as an offensive weapon to assert dominance during this period.