Duck-billed Platypus

## About

A platypus underwater at the Platypus House, Tasmania.

## Background Information

### Alternate Name(s)

Platypus, Duckmole, Duckbill, Ornithorhynchus, Watermole, Boondaburra, Mallingong, Tambreet, Matakupay, Gaya-dari, Lare-re-lar,

## Classification

### Species

O. anatinus (formerly P. anatinus)

The duck-billed platypus ***(Ornithorhynchus anatinus)*** also simply known as the platypus, is one of two remaining monotreme species native to Australia. The platypus has a narrow body that is covered with dark brown fur and silverish underfur, that transitions to a lighter cream or white colour on the underbelly. This is known as counter-shading and allows the platypus to remain undetected by aquatic predators from underneath and predators above. The eyes are brown and lined with the same colouration on the underbelly. The ears and eyes are close to one another and a channel of dark naked skin connects the two, forming an eyebrow-like appearance. The tail of the platypus is often represented as being orange in colour and hairless in media however, in reality, the tail is covered in coarse dark brown hairs, that darken towards the tail's end. Platypuses have duck-like bills however, this is not a way of impersonating or mimicking duck species and it is rather an evolutionary coincidence, as the larger surface area of the bill allows for greater electroreception when hunting. It is soft and leathery in texture and it is greyish-blue in colour. The platypus also has large, flat, clawed, webbed-feet with five digits. The front pair act as a way of paddling through the water, while the hind pair turn the platypus while underwater. On males, the hind legs have venomous barbs on their ankles, known as spurs. Spurs are most frequently used to compete with other males during breeding season (discussed in Behaviour). The name '*platypus*' is an English name that is derived from the Greek "*platúpous"* (πλατύπους). This word is comprised from two words; "*platús"* (πλατύς) and "*poús"* (πούς), meaning; wide/broad and foot respectively. George Shaw (1751-1831), the first European scientist to describe the platypus in 1799, first believed that the specimen was a hoax. He thought it was the body of an undiscovered Australian beaver-like animal, stitched to the head of a duck. After the individual was sent back to Great Britain (now the United Kingdom), it was found to be an actual animal, as its body showed no evidence of the taxidermy process. Shaw originally wanted to name the species ***(Platypus anatinus)*** however, the genus name ***(Platypus)*** had already been in use by a group of beetle species. Many early British settlers would also use the terms "*watermole*" and "*duckmole*" to identify the animal. By the Aboriginal peoples of Australia, the platypus is known from a variety of names, including; boondaburra, tambreet and mallingong. The platypus is sexually dimorphic with males reaching up to 50cm (19.6in) and weighing 0.7-2.4kg (1-5lbs) while females reach 43cm (17in) and weigh 0.7-1.6kg (1-3.5lbs). Platypuses will vary in size regionally. For example, platypuses in Tasmania are much larger and darker than their mainland counterparts.

## Diet

The platypus is a carnivorous species, hunting mostly at night, foraging for 8-16 hours daily. It is known to consume various freshwater crustacean species, such as the common yabby ***(Cherax destructor)***, crayfishes and freshwater shrimp species. Platypuses commonly hunt invertebrates, such as aquatic insects like swimming beetles and water bugs as well as freshwater 'pea-shell' mussels ***(Pisidium ssp.)***. Snail and worm species are also a common prey item of the platypus. They have also been known to hunt larger species, such as juvenile fish, fish eggs and tadpoles. The species has also been known to catch moths and cicadas from the water's surface. Platypuses hunt using a method known as electroreception. As platypuses close their ears, eyes and nostrils while underwater, electroreception allows the platypus to hunt effectively without their most essential senses. Precisely how electroreception in platypuses works is unknown however, it is though the that three main receptor cells exist in the bill, in addition to thousands of smaller ones, culminating in a sensory super-organ that allows the platypus to detect drastic and subtle movements in the riverbed, by sensing electrical fields produced by other organisms. While hunting, the platypus will also use its bill like a sifter or shovel, scooping up the sediment in order to unearth small prey items, while larger prey items like yabbies, are caught separately. A platypus may uncommonly hunt for up to 30 hours at a time, often diving up to 1,600 times in a single sitting. The platypus has no stomach, its esophagus connecting directly to its intestine. This means that fat is stored in the tail. As a result of this, a platypus' health can be dictated by the thickness of its tail.

## Conservation Status

Climate factors and human intervention remain some of the platypus' largest threats. The use of freshwater deposits in agricultural settlements and industrial supplies, as well as common steam regulation has depleted the platypus' habitat substantially. Agricultural factors have also contributed to river bank erosion and water sedimentation. Combined with recent droughts and fires, available platypus range has declined in size in past years. One of the largest largest decreases in population and range of the platypus occurred in 2006, when frequent tropical cyclones that caused mass flooding eliminated much of the platypus' northern range, in Queensland. In the urbanised areas of its range, the platypus faces threats of poor habitat and water quality, as well as water contamination. Plastic litter and fishing nets/traps in particular are often found to be attached or entangled onto specimens, often causing serious injury or proving fatal. Hard metals are also likely to contaminate waters. The Tasmanian platypus subpopulation is under threat by a fungal disease known as mucormycosis, which eats away at tissue and causes long-lasting wounding and death. Throughout its range, the platypus is also killed commonly by invasive predators, such as foxes, dogs ***(Canis lupis familiaris)*** and feral ***(Felis silvestris)*** and domestic cats ***(Felis catus)***. Today, platypuses are listed as a near-threatened species by the IUCN.

## Range and Population

The platypus currently inhabits states of Queensland, New South Wales, Victoria, Tasmania and the Australian Capital Territory (A.C.T.) all located in Eastern Australia. The species was also likely once prevalent in the state of South Australia however, has since gone regionally extinct on its mainland. Historically, specimens preserved from this state were scarce, even during first European colonisation. During the 1920s, the species was reintroduced to the state, being implemented on Kangaroo island. The animals were placed there because concerns arose at the time surrounding their endangerment or extinction on the mainland. The species is prevalent throughout its modern southern range, occurring in 80% of river basins in Victoria, all of the state's east-flowing rivers and 80% of New South Wale's west-flowing rivers. In Queensland however, the species is infrequently seen, possibly as a result of excess flooding and predation by saltwater crocodiles ***(Crocodylus porosus)***. The species is noticeably absent from the west of the continent, not occurring currently or historically in Western Australia or the Northern Territory. This can be attributed to the increase in crocodile populations and the arid environments. Throughout its entire range, the platypus inhabits inland wetlands, preferring calmly flowing rivers over lakes and ponds. Platypuses have also been found living in saltwater lagoons and estuaries around the mouths of rivers, though this is uncommon and the species is not a marine mammal. They occur frequently in forested areas, such as bushlands and rainforests. The platypus' population ranges from 30,000-300,000 mature individuals (as of 2016) and it is currently in decline. This number may be inaccurate however, as platypus numbers are hard to count and monitor.

## Behaviour

The platypus is a mostly aquatic species, being adapted almost entirely for a submerged environment, having a narrow and streamlined body and legs that come out of its sides, similarly to a reptile. Due to these adaptations, the platypus is clumsy on land, waddling awkwardly and slowly. This morphology causes platypuses to exert up to 30% more energy travelling on land when compared to in water. Due to the platypus' hunting method of electroreception, when foraging, the species will shift its head from side-to-side quickly while swimming closely to the river bed. After hunting, a platypus will hold its catch inside of its interior cheek pouches and then float on top of the water's surface. The platypus remains buoyant subconsciously, as it has a insulated layer of air in its fur, acting as a float or buoy. Sometimes, a platypus may also scoop up sediment with its catch. This is likely purposeful, as the sediment allows the platypus to grind up its food, in the absence of teeth. Grooves on the species' bill expel excess water and sediment however, much of the time, the platypus will also consume some sediment. In terms of social behaviours, platypuses have been noted as mostly solitary and territorial animals however, their attitude towards company differs among sexes. An average platypus home range can be up to 0.37-7km (0.22-4.3mi) though, range may differ greatly in size depending on the environment and other factors. Female platypuses do not mind being accompanied by other females in their home range, whereas males are much more territorial, even going out of their way to change their foraging times when accompanied by other males in their home range, simply to avoid each other. The platypus is also known to exhibit very limited communication (due to the species' solitary lifestyle), rarely emitting any form of noise at all. In captivity however, it has been recorded that the platypus may emit a growling, gurgling or purring-like call. It is unknown what this call signifies in terms of communication. In reproductive and breeding behaviours, the platypus exhibits a polygamous mating system and seasonal breeding. The platypus does exhibit courting acts and they are fairly well-documented. The male platypus is most likely to initiate the interaction however, the female's willingness dictates his success. He will bite down softly on the female's tail after swimming closely to her. If she is not receptive, she will quickly swim away, darting through underwater foliage and debris in order to escape. If she is receptive however, she will allow the male to bite her tail and stay close to him. The male will then wrap around the female, holding his tail beneath her side, before biting closer to the female's neck or shoulders. Other details are unknown due to the species' enigmatic behaviour. During this breeding season, it is likely that male on male competition is very common, as spur-wounds are common during this time. The platypus' spur is a venomous defense mechanism that only male individuals possess. its secondary use is as a weapon against predators. After mating, the female will have an estimated gestation of 27 days, laying 2-3 leathery eggs in a burrow she constructed. The incubation likely lasts 6-10 days and she will press her eggs against her underbelly with her tail during this period. Lactation will last typically around 3-4 months and as the female platypus lacks nipples or teats, the milk is expelled through glands on the skin, collecting in grooves, similarly to sweat. The platypus has also recently been found to have bioluminescent qualities in its fur. It glows green and blue under blacklight and the reasoning for this is unknown.

### Relationship with Humans

The platypus is significant species in many Aboriginal cultures, where it goes by various different names. The platypus was most important for the Aboriginals as a food source, commonly being hunted. The tail of the platypus is particularly sought after and nutritious. The species is also rooted within Aboriginal Dreamtime culture, where it was said to have been a hybrid of a duck and a rakali ***(Hydromys chrysogaster)***. The story of the platypus originates from the upper Darling river of eastern Australia and follows a young female duck who wanders away from her tribe and is kidnapped by a rakali named Biggoon. After escaping from Biggoon for a short time, the duck returns to lay two eggs in his den, of which two platypuses hatched. The family was exiled and made to live in the mountains of Australia. Another story of the same region tells that the platypus was asked to join either the tribes of the water animals, the land animals or the birds. The platypus decided not to join any of the groups, wishing to remain friendly with all of the animals. The platypus is also assigned as a totem animal to many Aboriginal people. For these people the platypus is a spiritual emblem and source of cultural identity. The Wadi Wadi people of the Murray river in particular, See the platypus as a significant species that coincides with their spiritual and cultural connection to their land. As a result, the people protect and conserve the platypus. After colonisation, the platypus was hunted often for its fur for the its use in clothing and accessories. The platypus was also hunted and captured by early explorers and settlers in desperation to feel superior to their peers. This extreme hunting would come to a forced stop in 1912, with the legal protection of the platypus. In the modern day, the platypus in undoubtably a great sense of identity for the Australian people. One of the most notable displays of the country's love for the platypus would come in the form of the post WW2 platypus gifting that the Australian government executed, where live specimens were gifted to the allied forces in the 1940s. Also around the same time (1943 exactly), Winston Churchill (1874-1965) demanded a platypus from the Australian government in an attempt to strengthen the United Kingdom's ties to the country. Though a lone male was shipped, it unfortunately perished on the voyage. Later in 1966, the platypus was introduced onto the design of the Australian 20 cent coin, replacing the previous florin. It remains on the currency presently.

## In Captivity

The platypus has a long history in captivity, starting in 1939, where the National Geographic Magazine published an article on the platypus and the efforts at the time made to raise the platypus in a captive environment. The first platypus was born in captivity on the 26th of February, 1943, in Healesville Sanctuary, Victoria. This and the breeding that occurred in 2003 at Taronga zoo, New South Wales, remain the only zoos to successfully breed the species. Healesville actually continues regular platypus breeding presently. The platypus is almost exclusively found in Australian institutes, with other notable facilities being Melbourne zoo, Victoria and the Platypus house, Tasmania. One zoo outside of Australia, the San Diego zoo has successfully housed platypuses. The zoo attained a male-female pair of platypuses in the October of 2019 and they remain at the zoo currently. San Diego aims to raise awareness for the species internationally. Bronx zoo has attempted to captivate the platypus in the past in the years; 1922, 1947 and 1958 however, only two of their specimens lived past 18 months at the zoo.

## Sources

* IUCN Red List of Threatened Species - https://www.iucnredlist.org/species/40488/21964009
* Duck-billed Platypus | Animal Diversity Web, University of Michigan Museum of Zoology - https://animaldiversity.org/accounts/Ornithorhynchus\_anatinus/
* Australian Platypus Conservancy - https://platypus.asn.au/
* Platypus | Australian Museum - https://australian.museum/learn/animals/mammals/platypus/
* Platypus | Wikipedia - https://en.wikipedia.org/wiki/Platypus
* Duck-billed Platypus | ZOOINSTITUTES - https://zooinstitutes.com/animals/duck-billed-platypus-1167/
* The Prime Minister and the Platypus: a paradox goes to war | National Library of Medicine - https://pubmed.ncbi.nlm.nih.gov/22326098/#:~:text=In%20February%201943%2C%20in%20the,shortly%20before%20arrival%20in%20Britain.
* Kangaroo island Wildlife | Responsible Travel - https://www.responsibletravel.com/holidays/kangaroo-island/travel-guide/wildlife