What species of duck is this?

What species of duck is this?

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What species of duck is this? See below photo. Head colour is green like a mallard, but that's pretty much the only similarity. Spotted in Leicestershire, UK.

Probably a domestic hybrid of a mallard.

From Cornell:

If your duck has large patches of white where you didn't expect it, think domestic duck.

Mallards (Anas platyrhynchos), which have the identifiable green head in the wild, are only 1 of 2 species of ducks that have been domesticated. So it would be no surprise if a strange looking mallard was in fact, well, a mallard.

Again, according to Cornell:

Another common form [of the domestic/hybrid mallard] is the bibbed version. It has a sort of normal body and head plumage, and a white chest.


The passion for weird plumage in domestic ducks does not stop with white, but can go the other way too. Some breeds are darker than normal Mallard plumage

These descriptions both match your specimen quite well.

Although your picture is low quality, it appears to me that the posterior feathers of your specimen also are not straight. Again, quoting Cornell:

Watch for the little curled feathers on the back of the male, above the tail. Only the Mallard and its domestic descendants have those.

Finally, most hybrid ducks that come from some domesticated origin tend to be larger than non-domesticated specimens since early domestication efforts emphasized large size for food (vs simply plumage for appearances). Your image has no relative scale, so I cannot comment on whether this applies to your specimen or not.

In terms of a specific "name" for such a hybrid?

I did find evidence that some people refer to domestic-hybrid mallards like your dark-plumage, white-bibbed mallards as "manky mallards", though I'm not sure how ubiquitous this is. For example, see here and here.

  • Though claims non-domesticated birds can also occasionally develop bibs similar to those seen on domesticated descendants.

I think it's likely a mallard hybrid. These sites have examples of crosses between mallards and domestic ducks (and others as well):

There isn't any specific pattern but the light coloring below the head seems to be a common occurrence in hybrids, with some variation in the rest of the coloring. It's hard to find more reputable resources because of the variation, but I don't know of any other duck that would fit the ID.

What species of duck is this? - Biology

Click through all of our Duck images in the gallery.

“A duck can sleep with one eye open in order to stay alert to predators”

Ducks are omnivorous eating plants, insects, small fish, seeds, and crustaceans. A duck is a bird known as a waterfowl because they live near ponds, rivers, and lakes. This animal lives on every continent except Antarctica. Some of them live in freshwater habitats while others live in saltwater. They have a lifespan of up to 10 years.

What species of duck is this? - Biology

Laysan duck

The Laysan duck was first reported on Lisianski Island in 1828. Its fortune changed for the worse in 1844 when shipwrecked sailors washed ashore, eating the duck and other native species to survive [1]. Of greater long-term impact, however, was the accidental introduction of mice (Mus musculus) to the island later that year by a rescue ship. A second shipwreck party washed ashore in 1846. By 1857 mice had denuded the island, destroying the duck's habitat. By 1916 the mouse and rabbit population starved to death due to lack of vegetation [1]. Unencumbered by vegetation, windblown sand filled in the island's freshwater springs. The Laysan duck was extirpated from Lisianski some time between 1845 and 1857.

The pre-exploitation population size on Laysan Island is not known but was described as "not very plentiful" in the winter of 1891 [1]. It was presumably larger than the current carrying capacity of about 500 birds because the extent of current habitat is known to be smaller than in the pre-exploitation period [2]. Laysan did not experience sustained human disturbance and was not colonized by humans until guano miners occupied it from 1891 to 1904 [5]. Within six months of arriving, they killed 300,000 nesting seabirds for food and sport. Their greatest impact, however, was the introduction of European rabbits (Oryctolagus cuniculus) which thoroughly denuded the island by the 1910s, reducing hiding cover and prey habitat, and allowing windblown sand to bury freshwater springs and reduce the size of the island's central hypersaline lake [4]. The extinction of 14 species including the Laysan rail, Laysan honeycreeper and Laysan millerbird have been linked to the rabbit invasion [3]. Laysan was made part of the Hawaiian Islands Bird Reservation in 1909, but was not policed, allowing Japanese feather hunters scoured it in 1909 and 1910, killing Laysan ducks for food and feathers. The species was nearly driven to extinction, being reduced to less than 100 birds in 1902 and just 7 adults in 1911 and 1912 [1].

Rabbit eradication efforts were unsuccessful in 1912 and 1913, but having denuded the island, the species starved to death by 1923 [5]. Laysan duck numbers slowly increased as the vegetation grew back, allowing the species to increase to about 500 birds by 1957 [1]. Intermittent surveys suggest that the species maintained a population of 400-600 birds from 1957 to 2005, with the exception of a dramatic population crash in late 1993 and early 1994 due to sustained drought [1]. The population grew steadily from the 1994 low point back to about 500 birds in 2004 [1].

In 1967, 12 birds were relocated to Southeast Island on Pearl and Hermes Reef, but were not seen in subsequent years. Twenty ducks were translocated to Midway Atoll National Wildlife Refuge in October, 2004 [2]. Nineteen birds, including six females were still alive in September, 2005. Five of the six females nested, fledging seven duckling four more birds may fledge by the end of the season [2]. Sixteen additional birds were released on Eastern Island and six on Sand Island in October 2005 [2]. During 2005, 12 ducklings successfully fledged on Sand Island, 11 of which survived as of January, 2006. The total Midway duck population as of January, 2006 was 51: 18 survivors from the 2004 release, 22 survivors from 2005 release, and 11 successful fledglings.

In the late 1950s, 33 birds were taken from Laysan into captivity [1]. Their offspring and seven additional wild birds were use to establish a colony at the Pohakuloa Endangered Species Facility on the Island of Hawai`i, but the colony proved unsuitable for reintroduction purposes. Captive breeding efforts ceased in Hawaii in 1989. As of 1999, 211 birds descended from 19 founders existed in 32 facilities worldwide [1]. While initially successful, captive breeding programs have experienced difficulties in recent years. While future conservation efforts in Hawaii may include establishing semi-wild populations, they are not expected to utilize any birds currently in captivity.

[email protected] of Nebraska - Lincoln

The 21 species of sea ducks are one of the larger subgroups (Tribe Mergini) of the waterfowl family Anatidae, and the 16 species (one historically extinct) that are native to North America represent the largest number to be found on any continent, and also the largest number of endemic sea duck species native to any continent.

Although generally not important as game birds, the sea ducks include some economically important birds such as the eiders, the basis for the Arctic eiderdown industry and a historically important food source for some Native American cultures. They also include what is probably the most northerly breeding species of all waterfowl and an icon of Arctic bird life, the long-tailed duck. The sea ducks also include species having some of the most complex and diverse pair-forming postural and acoustic displays of all waterfowl (goldeneyes and bufflehead), and some of the deepest diving species of all waterfowl (scoters and long-tailed duck). Sea ducks are highly prone to population disasters caused by oil spills and other water contaminants and, like other seabirds, are among the first bird groups that are being affected by current global warming trends in polar regions.

This book is an effort to summarize succinctly our current knowledge of sea duck biology and to provide a convenient survey of the vast technical literature on the group, with over 900 literature references. It also includes 90,000 words of text (more than 40 percent of which is new), 15 updated range maps, 11 black & white and 20 color photographs, over 30 ink drawings, and nearly 150 sketches.

Lastly, the North American sea ducks include the now extinct Labrador duck, the only northern hemisphere waterfowl species to have gone extinct in modern times. I have gratefully reprinted a Labrador duck watercolor by Sir Peter Scott. Considering recent population crashes in other sea ducks, such as the Steller’s eider and spectacled eider, it should also offer a sobering reminder of the fragility of our natural world and its inhabitants, including us.


When the platypus was first encountered by Europeans in 1798, a pelt and sketch were sent back to Great Britain by Captain John Hunter, the second Governor of New South Wales. [3] British scientists' initial hunch was that the attributes were a hoax. [4] George Shaw, who produced the first description of the animal in the Naturalist's Miscellany in 1799, stated it was impossible not to entertain doubts as to its genuine nature, [5] and Robert Knox believed it might have been produced by some Asian taxidermist. [4] It was thought that somebody had sewn a duck's beak onto the body of a beaver-like animal. Shaw even took a pair of scissors to the dried skin to check for stitches. [6] [5]

The common name "platypus" literally means 'flat-foot', deriving from the Greek word platúpous ( πλατύπους ), [7] from platús ( πλατύς 'broad, wide, flat') [8] and poús ( πούς 'foot'). [9] [10] Shaw initially assigned the species the Linnaean name Platypus anatinus when he described it, [11] but the genus term was quickly discovered to already be in use as the name of the wood-boring ambrosia beetle genus Platypus. [12] It was independently described as Ornithorhynchus paradoxus by Johann Blumenbach in 1800 (from a specimen given to him by Sir Joseph Banks) [13] and following the rules of priority of nomenclature, it was later officially recognised as Ornithorhynchus anatinus. [12]

The scientific name Ornithorhynchus anatinus literally means 'duck-like bird-snout', deriving its genus name from the Greek root ornith- ( όρνιθ 'bird') and the word rhúnkhos ( ῥύγχος 'snout'), and deriving its species name from Latin anatinus ('duck-like'). [11]

There is no universally-agreed plural form of "platypus" in the English language. Scientists generally use "platypuses" or simply "platypus". Colloquially, the term "platypi" is also used for the plural, although this is a form of pseudo-Latin [6] going by the word's Greek roots the plural would be "platypodes". Early British settlers called it by many names, such as "watermole", "duckbill", and "duckmole". [6] Occasionally it is specifically called the "duck-billed platypus".

In David Collins's account of the new colony 1788–1801, he describes coming across "an amphibious animal, of the mole species". His account includes a drawing of the animal. [14]

The body and the broad, flat tail of the platypus are covered with dense, brown, biofluorescent fur that traps a layer of insulating air to keep the animal warm. [6] [12] [15] The fur is waterproof, and the texture is akin to that of a mole. [16] The platypus uses its tail for storage of fat reserves (an adaptation also found in animals such as the Tasmanian devil [17] ). The webbing on the feet is more significant on the front feet and is folded back when walking on land. The elongated snout and lower jaw are covered in soft skin, forming the bill. 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. [12] Platypuses have been heard to emit a low growl when disturbed and a range of other vocalisations have been reported in captive specimens. [6]

Weight varies considerably from 0.7 to 2.4 kg (1 lb 9 oz to 5 lb 5 oz), with males being larger than females. Males average 50 cm (20 in) in total length, while females average 43 cm (17 in), [12] with substantial variation in average size from one region to another. 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. [18]

The platypus has an average body temperature of about 32 °C (90 °F) rather than the 37 °C (99 °F) typical of placental mammals. [19] 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. [20] [21]

Modern platypus young have three teeth in each of the maxillae (one premolar and two molars) and dentaries (three molars), which they lose before or just after leaving the breeding burrow [12] adults have heavily keratinised pads in their place. [12] The first upper and third lower cheek teeth of platypus nestlings are small, each having one principal cusp, while the other teeth have two main cusps. [22] The platypus jaw is constructed differently from that of other mammals, and the jaw-opening muscle is different. [12] 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 pre mammalian synapsids. However, the external opening of the ear still lies at the base of the jaw. [12] The platypus has extra bones in the shoulder girdle, including an interclavicle, which is not found in other mammals. [12] As in many other aquatic and semiaquatic vertebrates, the bones show osteosclerosis, increasing their density to provide ballast. [23] It has a reptilian gait, with the legs on the sides of the body, rather than underneath. [12] When on land, it engages in knuckle-walking on its front feet, to protect the webbing between the toes. [24]


While both male and female platypuses are born with ankle spurs, only the spurs on the male's back ankles deliver venom, [25] [26] [27] composed largely of defensin-like proteins (DLPs), three of which are unique to the platypus. [28] The DLPs are produced by the immune system of the platypus. The function of defensins is to cause lysis in pathogenic bacteria and viruses, but in platypuses they also are formed into venom for defence. Although powerful enough to kill smaller animals such as dogs, the venom is not lethal to humans, but the pain is so excruciating that the victim may be incapacitated. [28] [29] Oedema rapidly develops around the wound and gradually spreads throughout the affected limb. Information obtained from case histories and anecdotal evidence indicates the pain develops into a long-lasting hyperalgesia (a heightened sensitivity to pain) that persists for days or even months. [30] [31] 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 that do not develop (dropping off before the end of their first year) and lack functional crural glands. [12]

The venom appears to have a different function from those produced by non-mammalian species its effects are not life-threatening to humans, but nevertheless powerful enough to seriously impair the victim. Since only males produce venom and production rises during the breeding season, it may be used as an offensive weapon to assert dominance during this period. [28]

Similar spurs are found on many archaic mammal groups, indicating that this is an ancient characteristic for mammals as a whole, and not exclusive to the platypus or other monotremes. [32]


Monotremes are the only mammals (apart from at least one species of dolphin) [33] known to have a sense of electroreception: they locate their prey in part by detecting electric fields generated by muscular contractions. The platypus's electroreception is the most sensitive of any monotreme. [34] [35]

The electroreceptors are located in rostrocaudal rows in the skin of the bill, while mechanoreceptors (which detect touch) are uniformly distributed across the bill. The electrosensory area of the cerebral cortex is contained within the tactile somatosensory area, and some cortical cells receive input from both electroreceptors and mechanoreceptors, suggesting a close association between the tactile and electric senses. Both electroreceptors and mechanoreceptors in the bill dominate the somatotopic map of the platypus brain, in the same way human hands dominate the Penfield homunculus map. [36] [37]

The platypus can determine the direction of an electric source, perhaps by comparing differences in signal strength across the sheet of electroreceptors. This would explain the characteristic side-to-side motion of the animal's head while hunting. The cortical convergence of electrosensory and tactile inputs suggests a mechanism that determines the distance of prey that, when they move, emit both electrical signals and mechanical pressure pulses. The platypus uses the difference between arrival times of the two signals to sense distance. [35]

Feeding by neither sight nor smell, [38] the platypus closes its eyes, ears, and nose each time it dives. [39] Rather, when it digs in the bottom of streams with its bill, its electroreceptors detect tiny electric currents generated by muscular contractions of its prey, so enabling it to distinguish between animate and inanimate objects, which continuously stimulate its mechanoreceptors. [35] Experiments have shown the platypus will even react to an "artificial shrimp" if a small electric current is passed through it. [40]

Monotreme electrolocation probably evolved in order to allow the animals to forage in murky waters, and may be tied to their tooth loss. [41] The extinct Obdurodon was electroreceptive, but unlike the modern platypus it foraged pelagically (near the ocean surface). [41]

In recent studies it has been suggested that the eyes of the platypus are more similar to those of Pacific hagfish or Northern Hemisphere lampreys than to those of most tetrapods. The eyes also contain double cones, which most mammals do not have. [42]

Although the platypus's eyes are small and not used under water, several features indicate that vision played an important role in its ancestors. The corneal surface and the adjacent surface of the lens is flat while the posterior surface of the lens is steeply curved, similar to the eyes of other aquatic mammals such as otters and sea-lions. A temporal (ear side) concentration of retinal ganglion cells, important for binocular vision, indicates a role in predation, while the accompanying visual acuity is insufficient for such activities. Furthermore, this limited acuity is matched by a low cortical magnification, a small lateral geniculate nucleus and a large optic tectum, suggesting that the visual midbrain plays a more important role than the visual cortex, as in some rodents. These features suggest that the platypus has adapted to an aquatic and nocturnal lifestyle, developing its electrosensory system at the cost of its visual system an evolutionary process paralleled by the small number of electroreceptors in the short-beaked echidna, which dwells in dry environments, whilst the long-beaked echidna, which lives in moist environments, is intermediate between the other two monotremes. [36]


In 2020, research in biofluorescence revealed the platypus is one of the monotremes that glow when exposed to black light in a bluish-green colour. [43]

The platypus is semiaquatic, inhabiting small streams and rivers over an extensive range from the cold highlands of Tasmania and the Australian Alps to the tropical rainforests of coastal Queensland as far north as the base of the Cape York Peninsula. [44]

Inland, its distribution is not well known. It was considered extinct on the South Australian mainland, with the last sighting recorded at Renmark in 1975, [45] until some years after John Wamsley had created Warrawong Sanctuary (see below) in the 1980s, setting a platypus breeding program there, and it had subsequently closed. [46] [47] In 2017 there were some unconfirmed sightings downstream, outside the sanctuary, [45] and in October 2020 a nesting platypus was filmed inside the recently reopened sanctuary. [48] There is a population on Kangaroo Island [49] introduced in the 1920s, which was said to stand at 150 individuals in the Rocky River region of Flinders Chase National Park before the 2019–20 Australian bushfire season, in which large portions of the island burnt, decimating all wildlife. However, with the SA Department for Environment and Water recovery teams working hard to reinstate their habitat, there had been a number of sightings reported by April 2020. [50]

The platypus is no longer found in the main part of the Murray-Darling Basin, possibly due to the declining water quality brought about by extensive land clearing and irrigation schemes. [51] Along the coastal river systems, its distribution is unpredictable it appears to be absent from some relatively healthy rivers, and yet maintains a presence in others, for example, the lower Maribyrnong, that are quite degraded. [52]

In captivity, platypuses have survived to 17 years of age, and wild specimens have been recaptured when 11 years old. Mortality rates for adults in the wild appear to be low. [12] Natural predators include snakes, water rats, goannas, hawks, owls, and eagles. Low platypus numbers in northern Australia are possibly due to predation by crocodiles. [53] The introduction of red foxes in 1845 for hunting may have had some impact on its numbers on the mainland. [18] The platypus is generally regarded as nocturnal and crepuscular, but individuals are also active during the day, particularly when the sky is overcast. [54] [55] Its habitat bridges rivers and the riparian zone for both a food supply of prey species, and banks where it can dig resting and nesting burrows. [55] It may have a range of up to 7 km (4.3 mi), with a male's home range overlapping those of three or four females. [56]

The platypus is an excellent swimmer and spends much of its time in the water foraging for food. It has a very characteristic swimming style and no external ears. [57] Uniquely among mammals, it propels itself when swimming by an alternate rowing motion of the front feet although all four feet of the platypus are webbed, the hind feet (which are held against the body) do not assist in propulsion, but are used for steering in combination with the tail. [58] The species is endothermic, maintaining its body temperature at about 32 °C (90 °F), lower than most mammals, even while foraging for hours in water below 5 °C (41 °F). [12]

Dives normally last around 30 seconds, but can last longer, although few exceed the estimated aerobic limit of 40 seconds. Recovery at the surface between dives commonly takes from 10 to 20 seconds. [59] [60]

When not in the water, the platypus retires to a short, straight resting burrow of oval cross-section, nearly always in the riverbank not far above water level, and often hidden under a protective tangle of roots. [57]

The average sleep time of a platypus is said to be as long as 14 hours per day, possibly because it eats crustaceans, which provide a high level of calories. [61]

The platypus is a carnivore: it feeds on annelid worms, insect larvae, freshwater shrimp, and freshwater yabby (crayfish) that it digs out of the riverbed with its snout or catches while swimming. It uses cheek-pouches to carry prey to the surface, where it is eaten. [57] The platypus needs to eat about 20% of its own weight each day, which requires it to spend an average of 12 hours daily looking for food. [59]


When the platypus was first encountered by European naturalists, they were divided over whether the female lays eggs. (She does, finally confirmed by William Hay Caldwell's team in 1884.) [12] [28]

The species exhibits a single breeding season mating occurs between June and October, with some local variation taking place between different populations across its range. [53] Historical observation, mark-and-recapture studies, and preliminary investigations of population genetics indicate the possibility of both resident and transient members of populations, and suggest a polygynous mating system. [62] Females are thought likely to become sexually mature in their second year, with breeding confirmed still to take place in animals over nine years old. [62]

Outside the mating season, the platypus lives in a simple ground burrow, the entrance of which is about 30 cm (12 in) above the water level. After mating, the female constructs a deeper, more elaborate burrow up to 20 m (65 ft) long and blocked at intervals with plugs (which may act as a safeguard against rising waters or predators, or as a method of regulating humidity and temperature). [63] The male takes no part in caring for its young, and retreats to his year-long burrow. The female softens the ground in the burrow with dead, folded, wet leaves, and she fills the nest at the end of the tunnel with fallen leaves and reeds for bedding material. This material is dragged to the nest by tucking it underneath her curled tail. [6]

The female platypus has a pair of ovaries, but only the left one is functional. [54] The platypus's genes are a possible evolutionary link between the mammalian XY and bird/reptile ZW sex-determination systems because one of the platypus's five X chromosomes contains the DMRT1 gene, which birds possess on their Z chromosome. [64] It lays one to three (usually two) small, leathery eggs (similar to those of reptiles), about 11 mm ( 7 ⁄ 16 in) in diameter and slightly rounder than bird eggs. [65] The eggs develop in utero for about 28 days, with only about 10 days of external incubation (in contrast to a chicken egg, which spends about one day in tract and 21 days externally). [54] After laying her eggs, the female curls around them. The incubation period is divided into three phases. [66] In the first phase, the embryo has no functional organs and relies on the yolk sac for sustenance. The yolk is absorbed by the developing young. [67] During the second phase, the digits develop, and in the last phase, the egg tooth appears. [66]

Most mammal zygotes go through holoblastic cleavage, meaning that, following fertilisation, the ovum is split due to cell divisions into multiple, divisible daughter cells. This is in comparison to the more ancestral process of meroblastic cleavage, present in monotremes like the platypus and in non-mammals like reptiles and birds. In meroblastic cleavage, the ovum does not split completely. This causes the cells at the edge of the yolk to be cytoplasmically continuous with the egg's cytoplasm. This allows the yolk, which contains the embryo, to exchange waste and nutrients with the cytoplasm. [68]

There is no official term for platypus young, but the term "platypup" sees unofficial use. [69] Newly hatched platypuses are vulnerable, blind, and hairless, and are fed by the mother's milk. Although possessing mammary glands, the platypus lacks teats. Instead, milk is released through pores in the skin. The milk pools in grooves on her abdomen, allowing the young to lap it up. [6] [53] After they hatch, the offspring are suckled for three to four months. During incubation and weaning, the mother initially leaves the burrow only for short periods, to forage. When doing so, she creates a number of thin soil plugs along the length of the burrow, possibly to protect the young from predators pushing past these on her return forces water from her fur and allows the burrow to remain dry. [70] After about five weeks, the mother begins to spend more time away from her young and, at around four months, the young emerge from the burrow. [53] A platypus is born with teeth, but these drop out at a very early age, leaving the horny plates it uses to grind food. [71]

The platypus and other monotremes were very poorly understood, and some of the 19th century myths that grew up around them – for example, that the monotremes were "inferior" or quasireptilian – still endure. [73] In 1947, William King Gregory theorised that placental mammals and marsupials may have diverged earlier, and a subsequent branching divided the monotremes and marsupials, but later research and fossil discoveries have suggested this is incorrect. [73] [74] In fact, modern monotremes are the survivors of an early branching of the mammal tree, and a later branching is thought to have led to the marsupial and placental groups. [73] [75] Molecular clock and fossil dating suggest platypuses split from echidnas around 19–48 million years ago. [76]

The oldest discovered fossil of the modern platypus dates back to about 100,000 years ago, during the Quaternary period. The extinct monotremes Teinolophos and Steropodon were once thought to be closely related to the modern platypus, [74] but are now considered more basal taxa. [77] The fossilised Steropodon was discovered in New South Wales and is composed of an opalised lower jawbone with three molar teeth (whereas the adult contemporary platypus is toothless). The molar teeth were initially thought to be tribosphenic, which would have supported a variation of Gregory's theory, but later research has suggested, while they have three cusps, they evolved under a separate process. [78] The fossil is thought to be about 110 million years old, making it the oldest mammal fossil found in Australia. Unlike the modern platypus (and echidnas), Teinolophos lacked a beak. [77]

Monotrematum sudamericanum, another fossil relative of the platypus, has been found in Argentina, indicating monotremes were present in the supercontinent of Gondwana when the continents of South America and Australia were joined via Antarctica (until about 167 million years ago). [78] [79] A fossilised tooth of a giant platypus species, Obdurodon tharalkooschild, was dated 5–15 million years ago. Judging by the tooth, the animal measured 1.3 metres long, making it the largest platypus on record. [80]

Because of the early divergence from the therian mammals and the low numbers of extant monotreme species, the platypus is a frequent subject of research in evolutionary biology. In 2004, researchers at the Australian National University discovered the platypus has ten sex chromosomes, compared with two (XY) in most other mammals. These ten chromosomes form five unique pairs of XY in males and XX in females, i.e. males are X1Y1X2Y2X3Y3X4Y4X5Y5. [81] One of the X chromosomes of the platypus has great homology to the bird Z chromosome. [82] The platypus genome also has both reptilian and mammalian genes associated with egg fertilisation. [38] [83] Though the platypus lacks the mammalian sex-determining gene SRY, a study found that the mechanism of sex determination is the AMH gene on the oldest Y chromosome. [84] [85] A draft version of the platypus genome sequence was published in Nature on 8 May 2008, revealing both reptilian and mammalian elements, as well as two genes found previously only in birds, amphibians, and fish. More than 80% of the platypus's genes are common to the other mammals whose genomes have been sequenced. [38] An updated genome, the most complete on record, was published in 2021, together with the genome of the short-beaked echidna. [86]

Status and threats

Except for its loss from the state of South Australia, the platypus occupies the same general distribution as it did prior to European settlement of Australia. However, local changes and fragmentation of distribution due to human modification of its habitat are documented. Its historical abundance is unknown and its current abundance difficult to gauge, but it is assumed to have declined in numbers, although as of 1998 was still being considered as common over most of its current range. [55] The species was extensively hunted for its fur until the early years of the 20th century and, although protected throughout Australia since 1905, [70] until about 1950 it was still at risk of drowning in the nets of inland fisheries. [51]

The International Union for Conservation of Nature recategorised its status as "near threatened" in 2016. [87] The species is protected by law, but the only state in which it is listed as endangered is South Australia, under the National Parks and Wildlife Act 1972. In 2020 it has been recommended to be listed as a vulnerable species in Victoria under the state's Flora and Fauna Guarantee Act 1988. [88]

Habitat destruction

The platypus is not considered to be in immediate danger of extinction, because conservation measures have been successful, but it could be adversely affected by habitat disruption caused by dams, irrigation, pollution, netting, and trapping. Reduction of watercourse flows and water levels through excessive droughts and extraction of water for industrial, agricultural, and domestic supplies are also considered a threat. The IUCN lists the platypus on its Red List as "Near Threatened" [2] as assessed in 2016, when it was estimated that numbers had reduced by about 30 percent on average since European settlement. The animal is listed as endangered in South Australia, but it is not covered at all under the federal EPBC Act. [89] [90]

Researchers have worried for years that declines have been greater than assumed. [89] In January 2020, researchers from the University of New South Wales presented evidence that the platypus is at risk of extinction, due to a combination of extraction of water resources, land clearing, climate change and severe drought. [91] [92] The study predicted that, considering current threats, the animals' abundance would decline by 47%–66% and metapopulation occupancy by 22%–32% over 50 years, causing "extinction of local populations across about 40% of the range". Under projections of climate change projections to 2070, reduced habitat due to drought would lead to 51–73% reduced abundance and 36–56% reduced metapopulation occupancy within 50 years respectively. These predictions suggested that the species would fall under the "Vulnerable" classification. The authors stressed the need for national conservation efforts, which might include conducting more surveys, tracking trends, reduction of threats and improvement of river management to ensure healthy platypus habitat. [93] Co-author Gilad Bino is concerned that the estimates of the 2016 baseline numbers could be wrong, and numbers may have been reduced by as much as half already. [89]

A November 2020 report by scientists from the University of New South Wales, funded by a research grant from the Australian Conservation Foundation in collaboration with the World Wildlife Fund Australia and the Humane Society International Australia revealed that that platypus habitat in Australia had shrunk by 22 per cent in the previous 30 years, and recommended that the platypus should be listed as a threatened species under the EPBC Act. [94] Declines in population had been greatest in NSW, in particular in the Murray-Darling Basin. [95] [96] [88]


Platypuses generally suffer from few diseases in the wild however, as of 2008 there was concern in Tasmania about the potential impacts of a disease caused by the fungus Mucor amphibiorum. The disease (termed mucormycosis) affects only Tasmanian platypuses, and had not been observed in platypuses in mainland Australia. Affected platypuses can develop skin lesions or ulcers on various parts of their bodies, including their backs, tails, and legs. Mucormycosis can kill platypuses, death arising from secondary infection and by affecting the animals' ability to maintain body temperature and forage efficiently. The Biodiversity Conservation Branch at the Department of Primary Industries and Water collaborated with NRM north and University of Tasmania researchers to determine the impacts of the disease on Tasmanian platypuses, as well as the mechanism of transmission and spread of the disease. [97]

Platypus in wildlife sanctuaries

Much of the world was introduced to the platypus in 1939 when National Geographic Magazine published an article on the platypus and the efforts to study and raise it in captivity. The latter is a difficult task, and only a few young have been successfully raised since, notably at Healesville Sanctuary in Victoria. The leading figure in these efforts was David Fleay, who established a platypusary (a simulated stream in a tank) at the Healesville Sanctuary, where breeding was successful in 1943. [98] In 1972, he found a dead baby of about 50 days old, which had presumably been born in captivity, at his wildlife park at Burleigh Heads on the Gold Coast, Queensland. [99] Healesville repeated its success in 1998 and again in 2000 with a similar stream tank. [100] Since 2008, platypus has bred regularly at Healesville, [101] including second-generation (captive born themselves breeding in captivity). [102] Taronga Zoo in Sydney bred twins in 2003, and breeding was again successful there in 2006. [100]

Platypuses are kept at the following sanctuaries:


    , Gold Coast, Queensland , Fig Tree Pocket, Brisbane, Queensland [103] , The Gap, Brisbane, Queensland [104]
  • The Australian Platypus Park at Tarzali Lakes, Millaa Millaa, Queensland [105]

New South Wales

South Australia


    , near Melbourne, Victoria, where the platypus was first bred in captivity by naturalist David Fleay in 1943. [98] The first platypus "born" in captivity was named Corrie and was quite popular with the public. In 1955, three months before a new "platypussary" (after "aviary") was opened, she escaped from her pen into the nearby Badger Creek and was never recovered.

United States

As of 2019, the only platypuses in captivity outside of Australia are in the San Diego Zoo Safari Park in the U.S. state of California. [107] [108]

Three attempts were made to bring the animals to the Bronx Zoo, in 1922, 1947, and 1958 of these, only two of the three animals introduced in 1947 lived longer than eighteen months. [109]

Aboriginal Australians used to hunt platypuses for food (their fatty tails being particularly nutritious), while, after colonisation, Europeans hunted them for fur from the late 19th century and until 1912, when it was prohibited by law. In addition, European researchers captured and killed platypus or removed their eggs, partly in order to increase scientific knowledge, but also to gain prestige and outcompete rivals from different countries. [88]

The platypus has been a subject in the Dreamtime stories of Aboriginal Australians, some of whom believed the animal was a hybrid of a duck and a water rat. [110] : 57–60

According to one story of the upper Darling River, [88] the major animal groups, the land animals, water animals and birds, all competed for the platypus to join their respective groups, but the platypus ultimately decided to not join any of them, feeling that he did not need to be part of a group to be special, [110] : 83–85 and wished to remain friends with all of those groups. [88] Another Dreaming story emanate of the upper Darling tells of a young duck which ventured too far, ignoring the warnings of her tribe, and was kidnapped by a large water-rat called Biggoon. After managing to escape after some time, she returned and laid two eggs which hatched into strange furry creatures, so they were all banished and went to live in the mountains. [88]

The platypus is also used by some Aboriginal peoples as a totem, which is to them "a natural object, plant or animal that is inherited by members of a clan or family as their spiritual emblem", and the animal holds special meaning as a totem animal for the Wadi Wadi people, who live along the Murray River. Because of their cultural significance and importance in connection to country, the platypus is protected and conserved by these Indigenous peoples. [88]

The platypus has often been used as a symbol of Australia's cultural identity. In the 1940s, live platypuses were given to allies in the Second World War, in order to strengthen ties and boost morale. [88]

Platypuses have been used several times as mascots: Syd the platypus was one of the three mascots chosen for the Sydney 2000 Olympics along with an echidna and a kookaburra, [111] Expo Oz the platypus was the mascot for World Expo 88, which was held in Brisbane in 1988, [112] and Hexley the platypus is the mascot for the Darwin operating system, the BSD-based core of macOS and other operating systems from Apple Inc. [113]

Since the introduction of decimal currency to Australia in 1966, the embossed image of a platypus, designed and sculpted by Stuart Devlin, has appeared on the reverse (tails) side of the 20-cent coin. [114]

The platypus has frequently appeared in Australian postage stamps, most recently the 2015 "Native Animals" series and the 2016 "Australian Animals Monotremes" series. [115] [116]

In the American animated series Phineas and Ferb (2007–2015), the title characters own a pet platypus named Perry who, unknown to them, is a secret agent. The choice of a platypus was inspired by media underuse, as well as to exploit the animal's striking appearance. [117] As a character, Perry has been well received by both fans and critics. [118] [119] Additionally, show creator Dan Povenmire, who also wrote the character's theme song, said that its opening lyrics are based on the introductory sentence of the Platypus article on Wikipedia, copying the "semiaquatic egg-laying mammal" phrase word for word, and appending the phrase "of action". [120]

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  • "Southern Exposure". Eye of the Storm. 2000. Australian Broadcasting Corporation. Archived from the original on 7 May 2013. Platypus DVD EAN 9398710245592
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Guinea Fowl, Goose, Turkey, Ostrich, and Emu Eggs

Goose eggs

Geese have been commonly raised for egg and meat consumption since 3000 BC. Today, goose farming is the most popular in China, which contributes to about 90% of world’s goose population. Goose production is also relatively important in Egypt, Poland, and Hungary.

Of all farm animals, geese have undergone the least changes during the domestication process. Geese are still characterized by seasonal egg production of 12–70 eggs. In breeds of geese well known for their egg-laying capabilities, such as Chinese geese or their hybrids, annual production may exceed 90 eggs ( Dańczak et al., 1994 Mazanowski and Szukalski, 2000 Mazanowski and Kiełczewski, 2001 Mazanowski and Adamski, 2002, 2006 ). In contrast, native geese are characterized by a very short reproduction period and low egg output ( Dańczak et al., 1994 ).

Commercially raised breeder geese are usually kept for four consecutive seasons. Young geese usually do not come into lay before 9 months of age, with the typical age of maturity at 2 years of age. Too early of an onset of reproductive maturity (first oviposition in females) may adversely affect their reproductive performance during subsequent years ( Biesiada-Drzazga, 2014 ). Reproductive performance declines with age, with the fewest eggs laid during the forth year of production. In Europe, commercial breeder geese usually begin to lay in January or February. Most of the geese eggs are laid in March and April, and the least in June when the laying season ends ( Puchajda-Skowrońska, 2012 ).

The weight of an egg ranges from 120 to 175 g for young geese and from 160 to 190 g for older birds ( Table 4.1 , Mazanowski and Bernacki, 2006 Mazanowski, 2012 ). In the first reproductive season, the weight of a goose egg is smaller at the beginning of the season than later on. During the next years of production, egg weight is higher at the beginning of lay and declines progressively through the remaining season ( Mazanowski, 2012 ). Another factor affecting egg weight and composition is the genetic background of geese. Analysis of the morphological traits of eggs obtained from 3- to 4-year-old native Turkish geese of different plumage colors (black, white, piebald, and yellow) showed that they differ in egg weight. Piebald geese laid lighter eggs compared to white- and yellow-feathered birds. The same pattern was observed for the body weight of 1-day-old goslings ( Saatci et al., 2005 ).

The structural characteristics and quality of eggs from six Polish regional varieties of geese were compared, which represent a genetic reserve for this avian species ( Kisiel and Książkiewicz, 2004 ). The 3-year-old Lubelska, Kielecka, and Podkarpacka geese, originating from southern Poland, did not differ in egg weight (166.8–169.2 g), egg length (87.2–88.8 mm), and egg specific weight (1.089–1.093 g/cm 3 ) when compared to the Rypińska, Kartuska, and Suwalska geese (164.8–172.3 g 87.3–88.8 mm, and 1.088–1.090 g/cm 3 , respectively) from northern Poland. However, the geese varieties differed in egg width (57.2–59.0 mm), egg shape index (65.5–67.6%), and eggshell percentage (10.5–11.0%). Other studies ( Mazanowski et al., 2002, 2005 Mazanowski and Bernacki, 2003 ) evaluated the reproductive traits of hybrids obtained from crosses with Greylag, White Italian, and Slovakian geese. As an example, in high-producing 2-year-old hybrid geese (offspring from a White Italian male × Cuban goose female), that averaged 91 eggs in a season, egg laying was high at the beginning of the 28-week reproductive cycle but as the geese aged, egg production declined after the 21st week of lay along with egg weight as well as the proportion of shell which was also thinner with more pores. Egg contents also changed with age. Specifically, the proportion of thick albumen decreased with a concomitant increase in the proportion of yolk as geese aged ( Mazanowski and Adamski, 2006 ).

Goose eggs are mainly used for reproduction purposes, and those that fail to meet hatching egg requirements are fed to farm animals. Although goose eggs can be boiled and fried, humans do not usually consume goose eggs directly. Due to their oily taste, goose eggs are more commonly incorporated into baking cakes, cookies, confectionery products, and bakery goods ( Biesiada-Drzazga, 2014 ).

A goose egg weighing 162 g contains 57.2% albumen, 30.6% yolk, and 12.2% shell. It is most similar to a chicken egg in terms of proportions of yolk and shell ( Table 4.1 ). It is characterized by low water and relatively high protein contents. Fat content is higher than in other birds except for emu eggs, whereas ash percentage in goose egg is higher than in chicken, turkey, and guinea fowl eggs, but lower than in ratite eggs ( Table 4.2 ). Yolk is low in cholesterol (13.94 mg/g yolk) as compared to guinea fowl, turkey, and ostrich eggs, but is similar to chicken eggs. The yolk has a high proportion of SFA as compared to guinea fowl eggs, and the proportion of monounsaturated fatty acids is higher than chicken eggs ( Table 4.4 ). In addition, the interior content of a goose egg contains higher calcium, phosphorus, magnesium, iron, and zinc ( Table 4.5 ), as well as higher vitamins A, E, B1, B6, B12, but less B2 than chicken eggs ( Table 4.6 ). In addition, goose eggs are characterized by higher energy concentration (185 kcal/100 g of egg) compared to chicken eggs (143 kcal/100 g of egg, Agricultural Research Service, United States Department of Agriculture, National Nutrient Database, 2014 ).

Table 4.5 . Mineral Content of Whole, Fresh, Raw Eggs From Different Poultry Species

Chicken a (mg/100 g egg)Goose a (mg/100 g egg)Turkey a (mg/100 g egg)Ostrich b,c (mg/100 g egg)

Table 4.6 . Vitamin Content of Whole, Fresh, Raw Eggs From Different Poultry Species

Vitamin Concentration (per 100 g egg)Species
Chicken a Goose a Turkey a Ostrich b,c
Thiamine (B1)mg0.0400.1470.1100.150
Riboflavin (B2)mg0.4570.3820.4700.240
Pyridoxine (B6)mg0.1700.2360.131
Cobalamin (B12)μg0.8905.1001.690

It is essential that geese breeder flocks are fed nutritionally balanced diets that meet their protein, vitamin, and mineral requirements. An adequate supply of dietary nutrients provides the egg with sufficient components for normal embryo development, thus ensuring good hatchability and high-quality goslings. The improved nutritional value of goose eggs also makes them more suitable as table eggs ( Larbier and Leclercq, 1995 ).

The chemical composition of geese eggs can be modified through diet manipulation. The relatively stable components of eggs include water, protein, amino acids, fat and water-soluble vitamins, calcium, phosphorus, magnesium, whereas the variable components include fatty acids, fat-soluble vitamins, B group vitamins, manganese, and iodine ( Naber, 1979 Bączkowska and Slósarz, 1987 ). Similar to chickens, the composition of geese eggs can be modified by increasing the yolk content of n−3 PUFA through the dietary addition of flaxseed meal to the female breeder diet ( Chen et al., 2014 ).

An increase in the ratio of plasma low-density lipoproteins cholesterol to high-density lipoproteins cholesterol occurred in human males, aged 50–62 years, after eating one goose or turkey egg for 30 consecutive days, which is detrimental to human health because it increases the risk of coronary heart disease ( Golzar Adabi et al., 2011 ). Consumption of chicken, quail, or ostrich eggs (30 days one egg per day) caused only a slight elevation in the low-density lipoproteins cholesterol to high-density lipoproteins cholesterol ratio, which shows that the eggs from these poultry species can be consumed (one a day) for 30 consecutive days without creating health issues.

What species of duck is this? - Biology

The Waterfowl Harvest Survey only asks about harvest of ducks, geese, sea ducks, and brant. Why? However, it is possible to identify duck species from their wing plumage and geese from their tail feathers. The US Fish & Wildlife Service has created a series of videos on duck identification using wing feathers. The following video is the first in the series, and shows you how to tell a female "hen" mallard from a male "drake" mallard that doesn't have its bright breeding plumage (i.e., hasn't "colored up") yet, just by looking at their wings.

But first, click on the image to learn the different feather groupings of a wing that are key to identifying duck species! This graphic is helpful when distinguishing between species as shown in the various videos on this page. See further down on this page for other videos in the series about duck species identification using wings.

The Waterfowl Parts Collection Survey randomly selects 5,000&ndash6,000 waterfowl hunters to send us a wing from every duck, and tail feathers from every goose, they shoot during the hunting season. This survey tells us the species composition of each state's duck and goose harvests. The image to the left shows the postage-paid envelope the selected waterfowl hunters send us for every individual bird they shoot during the hunting season. Once we receive the envelopes, biologists and volunteers gather together and sort through the wings and feathers to identify the species. The image above and to the right shows a stack of received envelopes and a duck wing ready for identification.

We combine Parts information with the estimates of harvest from the Diary Survey to get estimates of how many birds of each species were harvested.

We can also identify the sex of a duck from its wing, and whether it was a young-of-the-year bird or an adult. The ratio of young-of-the-year birds to adults gives a good measure of the production of each species compared to previous years. That, in turn, helps biologists keep track of how waterfowl populations are faring. The USFWS also measures annual production of dove, woodcock, and band-tailed pigeons with Parts Collection Surveys.

Duck wing identification can be a handy skill when you're having a good day in the duck blind, since you're only allowed to shoot one or two of some species. Male ducks are usually (but not always) easy to identify, but young-of-the-year females of several species are pretty drab "brown ducks" and look similar.

What is the duck on the right? Click the binoculars to find out the answer!

This content was developed through a collaboration between staff from the USFWS Migratory Bird Program and USGS Patuxent Wildlife Research Center. The project was kicked off at an internal 2017 National Civic Day of Hacking event held at PWRC. Participants included Tony Bethea, Theo Burton, Tony Celis-Murillo, Chris Deets, Rob Fowler, Pam Garrettson, Kayt Jonsson, Jenn Malpass, Derek Masaki, Paul Padding, Bob Raftovich, Becky Rau, Emily Silverman, Alli Sussman, Khristi Wilkins, and Nathan Zimpfer.


Authority:The information requested is authorized by the Migratory Bird Treaty Act (16 U.S.C. 703-712).

Purpose:The contact information is requested in case verification is needed about submitted migratory bird harvest information in the Migratory Bird Harvest Surveys

Routine Uses:The contact information may be used by staff from the Division of Migratory Bird Management to send reminders about the survey. More information about the routine uses may be found in the Systems of Records Notice, FWS-26 Migratory Bird Population and Harvest Systems.

Disclosure:The contact information requested in this form is voluntary.

Results and Discussion

Genotypic differentiation between Anas platyrhynchos and other duck species

We screened 364 SNPs developed for the mallard, Anas platyrhynchos, [14] in the genomes of six duck species, five of genus Anas and one of Aythya, the latter mainly for outgroup comparison: Anas platyrhynchos (N = 197), Anas acuta (northern pintail, N = 7), Anas crecca, (common teal, N = 9), Anas penelope (Eurasian wigeon, N = 14), Anas strepera (gadwall, N = 10) and Aythya fuligula (tufted duck, N = 17). The SNPs were evaluated for minor allele frequency (MAF) spectrum, Hardy-Weinberg equilibrium and linkage disequilibrium in Anas platyrhynchos from nine localities on three continents. The great majority of SNPs does not significantly deviate from neutrality and are unlinked.

We plotted the results of a series of principal component analyses (PCAs) for several combinations of individual of Anas platyrhynchos and other species genotypes. All plots are based on the first and second PCA axes. Other axes were investigated visually but did not provide further insight. No clear genetic clusters among specimens of Anas platyrhynchos were discernible in this analysis when analysed separately, and the evident absence of genetic structure in mallards is reflected by low values of explained variance in the first and second PCAs (Figure ​ (Figure2a). 2a ). Geography had no influence on genetic similarity. Even after correcting for potential mislabelling or outliers (see methods for details) a few individuals seem to lie a bit outside the main cluster, but note that the scaling of differences between Anas platyrhynchos individuals in this PCA is different from the scaling in analyses involving other duck species (see below). Interestingly, a lack of population structure in mallards has also been described on a continent-scale for mitochondrial data [15] and on a global scale using SNPs (Kraus et al., manuscript submitted). The other species form distinct clusters if analysed together (Figure ​ (Figure2b): 2b ): Anas penelope and Anas strepera form one cluster and are hard to distinguish from each other. Anas acuta and Anas crecca each form their own specific clusters. Aythya fuligula is of a different genus and hence not a dabbling duck. It serves as outgroup here and clearly lies outside these clusters. When individuals of all species are analysed jointly in this way (Figure ​ (Figure2c), 2c ), Anas platyrhynchos is clearly distinct from the other species. A putative hybrid between Anas acuta and Anas platyrhynchos is placed exactly in between its assumed parental species, thereby confirming its supposed hybrid status.

PCA analysis of duck genotypes. The program smartpca from the Eigenstrat package was used to calculate multivariate eigenvectors of the duck genotypes. The first two eigenvectors for each individual are plotted and colour coded by locality or species. The percent variation explained by PCA axes 1 and 2 is given in brackets. a) only Anas platyrhynchos individuals, colour coded by locality (see additional file 4). b) other ducks, colour coded by species: An. acuta (Anas acuta, ANAC), An. crecca (Anas crecca, ANCR), An. penelope (Anas penelope, ANPE), An. strepera (Anas strepera, ANST), Ay. fuligula (Aythya fuligula, AYFU). c) A joint calculation of PCA axes including all ducks analysed in this study. Additionally, a hybrid between Anas acuta and Anas platyrhynchos was included (ANACPLA), which is placed between the Anas platyrhynchos and Anas acuta cluster as expected. Anas platyrhynchos clearly forms an own cluster and the genetic similarity to the other species clusters reflects phylogenetic placements (i.e., Anas platyrhynchos is more closely related to Anas acuta and Anas crecca than to Anas penelope or Anas strepera).

SNP sharing among duck species is unexpectedly high

Genotyping was successful in the non-Anas platyrhynchos species with only 14-24% missing genotypes while within Anas platyrhynchos (for which the SNP set was originally designed) this number was 4%. Of 364 Anas platyrhynchos SNPs, 86 (24%) were polymorphic in Anas acuta, 102 (28%) in Anas crecca, 60 (16%) in Anas penelope, 41 (11%) in Anas strepera, and 11 (3%) in Aythya fuligula (Figure ​ (Figure3). 3 ). The proportion of shared SNPs between the Anas species are high compared with those reported in studies comparing other species with similar evolutionary distances. Bovines (cattle, bison and yak), for instance, have a relatively recent, Pleistocene radiation 2.5 million years ago (Mya), yet SNP sharing does not exceed 5% [16]. SNP sharing in the genus Gallus (chickens and relatives), another taxon with putative Pleistocene speciation and recent introgression from domestic animals, is also estimated at 5%[17], while in sheep (divergence time

3 Mya) it is estimated at only 1% [18]. The same low levels of SNP sharing also occur in invertebrate and plant species. The flies Drosophila pseudoobscura and D. miranda show 2.9% SNP sharing [19] (divergence time 3.7 Mya [20]) while the plant pairs Arabidopsis halleri/A. lyrata petraea and A. lyrata lyrata/A. l. petraea share 4.7% and 1.6%, respectively [21] (divergence times < 5 Mya). Given the divergence time of Anas platyrhynchos from, e.g., Anas acuta and Anas crecca of at least 6.4 Mya [22] (Figure ​ (Figure4) 4 ) they share up to an order of magnitude more SNPs than shown in these previous reports.

Venn diagram of shared SNPs with mallard by the four other Anas species. A core of 18 SNPs was polymorphic in all four Anas species. The closer phylogenetic relationship of Anas acuta and Anas crecca to Anas platyrhynchos is reflected in their polymorphism sharing pattern. Abbreviations as in Figure 2.

Schematic phylogram of the studied duck species. Branch lengths are scaled to Mya. Aythya fuligula was added as outgroup (branch length shortened at the split of the genus). Redrawn from [22] and Javier Gonzales (pers. comm.). An. codes for the genus Anas, and Ay. for Aythya.

Generally, the rate of SNP sharing in closely related species, as reported thus far, appears to be in the order of a few percent, at maximum. Random genetic drift usually purges polymorphisms as a function of time (generations), effective population size (Ne) and initial MAF, allowing an approximation of the time to fixation of allele frequencies under genetically neutral conditions [23]. For Anas platyrhynchos we estimate the mean persistence time (i.e., how long the polymorphisms segregate) for alleles with the highest possible MAF to be 5.3 million years, assuming a generation time of one year and Ne being constant at the present-day number. In the other duck species studied here it ranges between 0.8 and 2 million years. Rare alleles, e.g. MAF < 0.1, are lost more quickly (Table ​ (Table1). 1 ). The probability distribution for this loss has a long tail towards longer persistence times, with 5% of the shared polymorphisms with a MAF = 0.5 expected to be retained after a calculated threshold of 3.8Ne generations [24]. For Anas platyrhynchos this would equate to 7.2 million years (at a divergence from Anas crecca/Anas acuta of 6.4 Mya [22]). Thus, Anas platyrhynchos could have retained some of the ancestral shared polymorphisms since that split. However, Anas acuta and Anas crecca currently have much smaller Ne, and are unlikely to have retained more than 5% of their ancestral polymorphisms for periods longer than 2 and 2.6 million years (on the basis of 3.8Ne generations), if these species were reproductively fully isolated. Even with three times higher Ne or generation time, the number of shared SNPs between the studied duck species is higher than expected: the persistence times of the 5% fraction of SNPs with MAF = 0.5 for Anas acuta and Anas crecca (6.2 and 7.9 Mya) just exceed their divergence time from Anas platyrhynchos (6.4 Mya [22]). On the other hand, under these scenarios Anas penelope and Anas strepera would not have retained more than 5% of SNPs with MAF = 0.5 after 3.8 and 4.3 million years, respectively, at a minimum divergence time from Anas platyrhynchos of 8 Mya [22]. In conclusion, it seems the number of shared SNPs between the studied duck species exceeds what is likely under the neutral theory even when conservatively high estimates of Ne (from the upper bounds of the official counts) and conservatively low divergence times (mean times minus standard deviation of the values presented in [22]) are assumed.

Table 1

Interaction between population size and persistence time

Census size NcEffective size NePersistence time (mean)
p = 0.5p = 0.1

Population sizes Nc and Ne and mean persistence times in generations of the most balanced (p = 0.5 maximum frequency) and a rare (p = 0.1) SNP in each duck species. A ratio of 0.1 for Ne/Nc was assumed (see methods for more info).

Increased population size by ongoing interspecific hybridisation

What can then explain the high level of shared polymorphisms? We argue that these (and other closely related) duck species are part of a superspecies complex, here defined as a group of distinct species that frequently hybridise, with fertile offspring as the result. The superspecies concept was put forward by Mayr in 1931 [25], as a translation of the German expression Artenkreis, based on the work of Rensch [26]. Initially, it was used to assign species status to allopatric "races" that were too distinct to be lumped into the same species [27-29] (superspecies sensu stricto). Later, the definition was widened by Kiriakoff [30] and Mayr and Short [31] to be no longer exclusive to allopatric populations. For the Anas platyrhynchos complex this concept has previously been used by Scherer [13]. Being aware that "superspecies" is not an official taxonomic category we here choose to use the term superspecies (sensu lato) to embrace the sympatric distribution of interbreeding duck species. In doing so, we do not attempt to redefine nomenclatural classification schemes, nor do we propose to change current nomenclature. The term superspecies is clearly "an evolutionary taxonomy category but not nomenclatural rank" [32], thus to be preferred when studying biological systems rather than nomenclature.

There is longstanding anecdotal, morphological and experimental evidence for high hybridisation rates in ducks [7,12,22], but molecular proof has been limited thus far. Two studies using mitochondrial DNA in the Anas rubripes/platyrhynchos [33] and Anas zonorhyncha/platyrhynchos [34] complexes confirm hybridisation between these species. These findings were corroborated by studies investigating one to two nuclear markers [35,36]. Our study, using shared polymorphisms at hundreds of independent loci across the entire genome provides a more powerful means of analysing gene pool connectivity between closely related species and our results are consistent with a high level of genetic transfer between species via hybrid production and backcrossing.

A STRUCTURE [37] analysis identified several cases where genetic admixture from other species seems supported by their genotypes. When all six duck species were analysed jointly with the genetic clustering software STRUCTURE, all non-Anas platyrhynchos individuals were assigned to the same cluster (Additional file 1). Anas acuta individuals in particular showed partial Anas platyrhynchos genome admixture, and many Anas platyrhynchos individuals displayed some admixture from other species. When Anas platyrhynchos individuals were excluded, STRUCTURE assigned Anas penelope, Anas strepera and Aythya fuligula individuals to their species specific clusters, although one Anas strepera individual (ANST001) was almost fully assigned to Anas penelope. Anas acuta and Anas crecca were lumped into one cluster, and the hybrid was correctly assigned to that cluster by only 50% of its genome (Additional file 2). Excluding the hybrid from analysis did not alter the assignment of these two species to the same cluster. The same data sets were analysed with comparable settings in the software InStruct [38], which does not assume Hardy-Weinberg equilibrium in the inferred populations, and yields qualitatively similar results as the STRUCTURE analysis. This may be direct evidence of partial gene pool sharing between species, hence the establishment of a superspecies complex.

For example, a superspecies complex comprising Anas platyrhynchos, Anas acuta and Anas crecca would have a joint census population size of 31 million individuals and hence an Ne of 3.1 million (see methods for sources and assumptions), although sub-division of this possible superspecies due to assortative mating makes this an over-estimate[39]. However, an Ne of 3.1 million results in a mean persistence time of almost 9 million years (for initial MAF = 0.5). With an estimated most recent common ancestor at 6.4 Mya, these species could have on average retained even SNPs of lower MAF = 0.2. We refer to this analysis as 'persistence time analysis'.

Species status and the supra-population concept

The ducks studied here have not only remained morphologically distinct, their genetic cluster species designation [2] is strongly supported by principal component analysis of SNP genotypes: we find clear genetic differentiation between Anas platyrhynchos and the other duck species, as well as among these (Figure ​ (Figure2c). 2c ). Even though all these species live in sympatry, such a combined population is highly structured by assortative mating. While geographical substructure would be indicated by the term "meta-population", the situation in ducks leads us to define a new term that does not have a geographical connotation: "supra-population". We define a supra-population as a group of individuals that are part of the same sympatric superspecies complex and within which natural hybridisation occurs. Individuals of a superspecies complex are genetically-connected hybridising species, in which species barriers are primarily maintained by pre-zygotic factors.

A new model of speciation in ducks

Genomic incompatibilities usually lead to irreversible post-zygotic isolation of populations, but other, reversible, barriers can also be strong drivers of speciation. Visual cues have been identified as drivers of speciation in sexually dimorphic bird species [8,40] while sexual imprinting alone can explain assortative mating in modeling studies [41]. An empirical example from another Anatid species, the snow goose Anser caerulescens, which has two wide ranging colour morphs, nicely illustrates the case [42]. At any rate, a model for speciation in ducks must be able to explain the observed pattern of genetic and morphological differentiation in spite of the high degree horizontal gene exchange.

Paleogeographic and paleoclimatic evidence suggest that ecological conditions have been favourable for a duck radiation 6-12 Mya. This late Miocene period was warm and humid [43,44], but in transition towards a colder climate. Precipitation remained relatively high [45-47], making wetlands abundant and turning large inland salt water bodies brackish or even freshwater (e.g., Lake Pannon in Eurasia [48-50]). Globally, during this transition towards a colder, wet climate tropical forests were largely replaced by open grasslands [51-53], a habitat well suited for ducks. The fossil record of ducks beyond the Pleistocene is still very poor [54] but the few studies on the subject suggest that morphological change in respective duck species has been very limited over the last few million years [55,56], after a larger waterfowl species turn-over 15-23 million years ago [57]. The first fossil that resembles Anas platyrhynchos is thought to be from the late Pliocene, about 5 Mya [58]. This is close to the suggested lower bound of divergence times of some Anas species in the latest phylogeny of Anatidae [22]. We propose that an Anas-like duck split into multiple sister morphs sympatrically and simultaneously at that time, subsequently diverging by assortative mating. Our results indicate that the resulting cluster of species still exchanges portions of their genomes. We argue that since branching off of the Anas clade at least 6 Mya these mostly sympatric species remain separate by isolating mechanisms other than genetic incompatibilities, mostly by assortative mating. Though we acknowledge that this speciation scenario rests on the assumption of widespread sympatry for millions of years, we feel comfortable in making this claim. Although we only sampled five species for the present study, our model system sensu lato is the specious genus Anas, and even though species distributions change over time there certainly have always been several Anas species living in sympatry.

Theoretical studies suggest that sexual imprinting can drive speciation even in sympatry [59]. Moreover, experimental manipulations clearly demonstrate that individuals of Anas platyrhynchos can be imprinted on nearly any species of waterfowl but when raised in isolation they recognise conspecifics as mates [60]. This suggests that imprinting is important but incomplete in ducks genetic factors also contribute to mate recognition. The presence of assortative mating and recognition mechanisms are prerequisites for sympatric speciation leading to a superspecies complex around Anas platyrhynchos.

Dinosaurs Mingled with Cousins of Ducks and Chickens

Evolutionary cousins of chickens and ducks roamed the Earth with dinosaurs more than 65 millions years ago, according to a new study that runs counter to a key assumption about when birds got their footing on the planet.

The newly identified bird species, Vegavis iaai, lived during the Cretaceous period some 65 million years ago. This species somehow survived the Cretaceous/Tertiary (K/T) mass extinction event that wiped out the dinosaurs. They belonged to the class Aves, which includes radiations of all living birds.

Specifically, Vegavis belonged to an order of Aves called Anserifomes, which includes waterfowl. Within this order, Vegavis is most closely related to true ducks and geese, in the family Anatidae. It is not considered a direct ancestor of modern ducks or chickens, however.

Julia Clarke of North Carolina State University led the research team that re-examined a fossil found in Antarctica in 1992. New analysis using computer tomography (CT) scans gave a better view of the rock-encased bone than previous attempts. The images of the partial skeleton revealed that Vegavis was a new species and revealed its importance to avian evolution.

"We have more data than ever to propose at least the beginnings of the radiation of all living birds in the Cretaceous," Clarke says. "We now know that duck and chicken relatives coexisted with non-avian dinosaurs. This does not mean that today's chicken and duck species lived with non-avian dinosaurs, but that the evolutionary lineages leading to today's chicken and duck species did."

The first known bird, Archaeopteryx, lived 147 million years ago, but it is commonly believed that it was an evolutionary dead-end and its descendants never gave rise to modern birds.

Clarke's findings, as reported in the Jan. 20 edition of Nature, provide the first proof that cousins of living bird species co-existed with dinosaurs.

Before the classification of Vegavis, the fossil record of living bird lineages in the Cretaceous period was very unreliable. Some scientists supported a "big bang" theory of bird evolution, where today's living bird lineages only became established after non-avian dinosaurs were wiped out by the K/T mass extinction.

Clarke's findings dispute the "big bang" theory of bird evolution and provide strong evidence that living bird lineages existed before the mass extinction.

The size of a duck’s penis depends on the company it keeps

Growing up in an all-male environment makes some duck species grow larger penises.

The sight of ducks swimming on the placid surface of a picturesque lake is likely to prompt reflections on the harmonious balance of nature and the peaceful disposition of aviankind.

To entertain these ideas, however, while pleasant, is well wide of the mark. Beneath the water’s lapping meniscus – indeed, beneath the ducks themselves – a ruthless battle for genetic dominance is taking place. To the victor go the spoils, and in this case the symbol of triumph is (pardon us) the biggest penis in the pond.

Most species of birds do not have penises, but ducks are a noted exception, possessing substantial members. Indeed, the biggest penis of any animal, relative to body size, belongs to the Argentine duck (Oxyura vittata), which boasts an organ that runs to a frankly eye-watering 43 centimetres long.

While other species have not evolved to wield quite such improbable appendages, all male ducks sport sizeable willies. Not all, however, are equal, with some species having penises a tad – relatively speaking – on the short side.

In a bid to find out why, ornithologist Patricia Brennan of Mount Holyoke College in Massachusetts, US, and colleagues, decided to test the influence of duck society on duck genitalia.

In a study reported in the journal The Auk, Brennan’s team recount setting up captive colonies of two species. The first, called ruddy ducks (Oxyura jamaicensis), are entirely promiscuous and have very long penises. The second, lesser scaups (Aythya affinis), are monogamous during the breeding season and have relatively small ones (for a duck that is it’s still big enough to make a donkey wince).

Birds from each species were separated into two cohorts for two breeding season cycles: the first cohort was divided into male-female pairs and the second comprised an all-male group.

Brennan and her colleagues found that when kept in an all-male group, the lesser scaups all grew longer organs. This was in line with predictions, with genitalia length conferring a competitive advantage.

For the normally well-hung ruddy ducks, however, the results were more complicated. Some members of the all-male group did not reach sexual maturity until their second year. All of the ducks, when reaching maturity, grew penises faster than average, but many remained in reproductive readiness for shorter than normal periods.

The scientists suggest that by staggering their sexual maturity and readiness, the ducks were able to reduce in-group competition and male-to-male aggression, thereby optimising their abilities to procreate in a sub-optimal situation.

The results indicate that lesser scaups increase penis length in response to competition. The lengthening effect was less pronounced among the ruddy ducks, but that might have been, Brennan’s team suggests, because they already sport one of the biggest in the business and room for extension is therefore limited.

(For more information about duck penises, by the way, we recommend an excellent pop-science book written by Australian palaeontologist John Long. It is called Hung Like An Argentine Duck.)

Andrew Masterson

Andrew Masterson is a former editor of Cosmos.

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