King Island emu

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King Island emu
Adult and juvenile specimens,
Muséum national d'Histoire naturelle, Paris; the juvenile could possibly also be from Kangaroo Island

Extinct (1822)  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Infraclass: Palaeognathae
Order: Casuariiformes
Family: Casuariidae
Genus: Dromaius
Species:
D. novaehollandiae
Subspecies:
†D. n. minor
Trinomial name
†Dromaius novaehollandiae minor
(Spencer, 1906)
Historical distribution of emu taxa (King Island emu in red) and ancient shorelines around Tasmania
Synonyms
List
  • Casuarius diemenianus Jennings,1827
  • Dromaeus parvulus
    Broderip
    , 1842
  • Dromaeus minor Spencer, 1906
  • Dromaius peroni Rothschild, 1907
  • Dromaius bassi Legge, 1907
  • Dromaius parvulus Mathews, 1910
  • Dromiceius spenceri Mathews, 1912
  • Peronista peroni (Mathews, 1913)
  • Dromaius diemenianus (Morgan & Sutton, 1928)

The King Island emu (Dromaius novaehollandiae minor) is an

incubated
by both parents.

Europeans discovered the King Island emu in 1802 during early expeditions to the island, and most of what is known about the bird in life comes from an interview French naturalist

taxonomically
distinct, so their status remained unclear until more than a century later. Hunting pressure and fires started by early settlers on King Island likely drove the wild population to extinction by 1805. The captive specimens in Paris both died in 1822 and are believed to have been the last of their kind.

Taxonomy

There was long confusion regarding the

cassowaries as "casoars" at the time, which has led to further confusion.[4]

The French naturalist

type specimen of his new species Dromaius peroni, named after the French naturalist François Péron, who is the main source of information about the bird in life.[10] Spencer reported more emu bones from King Island in 1910, which he compared to bones from Kangaroo Island which were by then considered to belong to D. peroni.[11] The Australian amateur ornithologist Gregory Mathews coined further names in the early 1910s, including a new genus name, Peronista, as he believed the King and Kangaroo Island birds were generically distinct from the mainland emu.[12]

Kangaroo Island emus
in 1910

Later writers claimed that the subfossil remains found on King and Kangaroo Islands were not discernibly different, and that they therefore belonged to the same

forensics to demonstrate that the mounted skin in Paris came from King Island, and that at least one live bird had been brought from each island.[16] All scientific names given to the Kangaroo Island emu were therefore based on specimens from King Island or were otherwise invalid, leaving it nameless. Based on later finds of subfossil material in 1984, the Australian ornithologist Shane A. Parker confirmed the separate geographic origin and distinct morphology of the King and Kangaroo Island emus, finding that the latter was larger. Parker named the Kangaroo Island bird Dromaius baudinianus, after Nicolas Baudin, the leader of the French expedition. The name Dromaius ater was kept for the King Island emu.[17]

There are few morphological differences that distinguish the extinct insular emus from the mainland emu besides their size, but all three taxa were most often considered distinct species. A 2011 study by the Australian geneticist Tim H. Heupink and colleagues of

IOC World Bird List, which used D. n. minor thereafter.[20]

In 2014–2015, the English palaeontologist

Julian Hume and colleagues conducted a search for emu fossils on King Island; no major palaeontological surveys had been done since the early 20th century, apart from discoveries made by the local natural historian Christian Robertson during the preceding thirty years. In 2014, Hume and colleagues found emu subfossils in Cape Wickham, but upon returning to the site in 2015, the area had been turned into a golf course, and the researchers were denied access to the site. They cautioned in 2018 that other fossiliferous sites on King Island were also under such threat, and highlighted the need to protect them. The researchers also identified an area near Surprise Bay where subfossils had been collected in 1906, but found it almost impossible to find more, since the area had been covered in grass in the meantime (the grass had previously been kept down by livestock).[6] In 2021, Hume and Robertson reported a King Island emu eggshell missing a few pieces, which Robertson had discovered in a sand dune during fieldwork. This the only known almost complete egg of this emu, glued together from broken pieces.[21][22]

Evolution

Only known skin (in the Natural History Museum of Geneva) and skeleton (in Paris) of the likewise small and extinct Kangaroo Island emu, which was often confused with the King Island subspecies

During the

last glacial maximum eventually isolated the island. As a result of phenotypic plasticity the King Island emu population possibly underwent a process of insular dwarfism.[18] Emu eggshells were also identified from Flinders Island (in the opposite, eastern end of the Bass Strait) in 2017, possibly representing a distinct taxon.[6]

According to the 2011 genetic study, the close relation between the King Island and mainland emus indicates that the former population was isolated from the latter relatively recently, due to sea level changes in the Bass Strait, as opposed to a founding emu lineage that diverged from the mainland emu far earlier and had subsequently gone extinct on the mainland.[18] Models of sea level change indicate that Tasmania, including King Island, was isolated from the Australian mainland around 14,000 years ago. Up to several thousand years later King Island was then separated from Tasmania.[23] This scenario would suggest that a population ancestral to both the King Island and Tasmanian emu was initially isolated from the mainland taxon, after which the King Island and Tasmanian populations were separated. This, in turn, indicates that the likewise extinct Tasmanian emu is probably as closely related to the mainland emu as is the King Island emu, with both the King Island and Tasmanian emu being more closely related to each other. Fossil emu taxa show an average size between that of the King Island emu and mainland emu. Hence, mainland emus can be regarded as a large or gigantic form.[18]

A 2018 study by Australian geneticist Vicki A. Thomson and colleagues (based on ancient bone, eggshell and feather samples) found that the emus of Kangaroo Island and Tasmania also represented sub-populations of the mainland emu, and therefore belonged in the same species. They also found that the size of the island emus scaled linearly to the size of the islands they inhabited (the King Island emu was the smallest, while the Tasmanian was the largest), while time in isolation did not affect their size. This suggest that island size was the important driver in dwarfism of these emus, probably due to limitation in resources, though the exact effect needs to be confirmed. The little genetic differentiation between island emus indicates their dwarfism evolved rapidly and independently since they became isolated from each other. King Island is 1,100 km2 (420 sq mi), and was isolated from Tasmania for 12,000 years, while 62,400 km2 (24,100 sq mi) Tasmania was itself isolated from mainland Australia for 14,000 years. Kangaroo Island is 4,400 km2 (1,700 sq mi) and was isolated from the mainland 10,000 years ago.[24] A 2020 genetic study of the only known Kangaroo Island emu skin by the French ornithologist Alice Cibois and colleagues also supported retaining the three island emus as subspecies, with the King Island emu as D. n. minor.[25]

Description

Size comparison between a human, the mainland emu, and the King Island emu

The King Island emu was the smallest type of emu and was about 44% or half of the size of the mainland bird. It was about 87 cm (34 in) tall. According to Péron's interview with the local English

genes commonly associated with melanism in birds, but proposed the dark colouration could be due to alternative genetic or non-genetic factors.[18]

Péron stated there was little difference between the sexes, but that the male was perhaps brighter in colouration and slightly larger. The juveniles were grey, while the chicks were striped like other emus. There were no seasonal variations in plumage.[13] Since the female mainland emus are on average larger than the males, and can turn brighter during the mating season, contrary to the norm in other bird species, the Australian museum curator Stephanie Pfennigwerth suggested that some of these observations may have been based on erroneous conventional wisdom.[4] Hume and Robinson also suggested female King Island emus were larger than the males, and that Cooper could have mistaken brooding males for females when he stated the males were larger.[21]

Subfossil remains of the King Island emu show that the

trochlea was more incurved towards the middle trochlea in the Kangaroo Island bird, whereas they were parallel in the King Island emu.[17]

Comparison of the cranium contour in mainland (A, B, C) and King Island emus (D, E)

The King Island emu and the mainland emu show few morphological differences other than their significant difference in size. Mathews stated that the legs and bill were shorter than those of the mainland emu, yet the toes were nearly of equal length, and therefore proportionally longer. The tarsus of the King Island emu was also three times longer than the

cranium. However, the distal foramen is known to be variable in the mainland emu showing particular diversity between juvenile and adult forms and is therefore taxonomically insignificant.[26] The same is true of the contour of the cranium, which is more dome-shaped in the King Island emu, a feature that is also seen in juvenile mainland emus.[18]

Behaviour and ecology

1893 illustration by John Gerrard Keulemans based on the Paris skin (left), and 1907 version of same

Péron's interview described some aspects of the behaviour of the King Island emu. He wrote that the bird was generally solitary but gathered in flocks of ten to twenty at breeding time, then wandered off in pairs. They ate berries, grass and seaweed, and foraged mainly during morning and evening. They were swift runners, but were apparently slower than the mainland birds, due to being fat. They swam well, but only did so when necessary. They reportedly liked the shade of lagoons and the shoreline, rather than open areas. They used a claw on each wing for scratching themselves. If unable to flee from the

hunting dogs of the sealers, they would defend themselves by kicking, which could inflict a great deal of harm.[13][27]

The English Captain

preservation bias, they suggested that the emus were restricted to coastal and more open inland areas, and not found in the dense interior forests. An 1802 report by the English surveyor Charles Grimes also supported this, stating there were "plenty on the coast–but not inland". The tall, dense eucalypt forests of the island have since been destroyed.[6]

Breeding

Charles Alexandre Lesueur's 1807 plate of the head, wing and feathers of a possible King Island emu

Péron stated that the nest was usually situated near water and on the ground under the shade of a bush. It was constructed of sticks and lined with dead leaves and moss; it was oval in shape and not very deep. He claimed that seven to nine eggs were laid always on 25 and 26 July, but the selective advantage of this breeding synchronisation is unknown. The female

crows with its beak, but this is now known to be strictly male behaviour.[4]

Hume and Robertson compared the eggs of all emu taxa in 2021, and found that the eggs of the island dwarf emus were within or close to the size and smallest volume and mass ranges for mainland birds, with seemingly thinner eggshells. The egg of the mainland emu weighs 1.3 lbs. (0.59 kilograms) and has a volume of about 0.14 gallons (539 milliliters), while those of the King Island emu weighed 1.2 lbs. (0.54 kg) and had a volume of 0.12 gallons (465 mL). The egg mass of the mainland emu accounts for 1.6% of its body mass, whereas the egg mass of the King Island emu accounted for 2.3% of its body mass, even though it was 44% lighter than the mainland bird. Hume and Robertson attempted to explain these findings, and noted that emus and other

precocial juveniles, that is, relatively mature and mobile when they hatch, and appear to have laid their eggs at the same time.[21][22]

Hume and Robertson suggested the evolutionary advantage for the small emus in retaining large eggs and precocial chicks was driven mainly by limited food resources on their islands. Their chicks had to be large enough to feed on seasonably available food, and possibly to develop

morphometrically similar to the King Island emu, and has a similar breeding strategy.[21][22]

Relationship with humans

1807 cartouche of a small emu and other birds from a map of south east Australia and Kangaroo Island
Self portrait of Lesueur lying on a cage containing birds in the ship Le Géographe

The emus of King Island were first recorded by Europeans when a party from the British ship Lady Nelson, led by the Scottish explorer John Murray, visited the island in January 1802. Murray noted on 12 January that "they found feathers of emus and a dead one", but some days later they found "woods full of kangaroo, emus, badgers, etc.", and one emu was "caught by the dog about 50 lbs weight and surprisingly fat." The bird was sporadically mentioned by travellers henceforward, but not in detail.[4] Captain Nicolas Baudin visited King Island later in 1802, during an 1800–04 French expedition to map the coast of Australia. Two ships, Le Naturaliste and Le Géographe, were part of the expedition, which also brought along naturalists who described the local wildlife.[13] Péron visited King Island and was the last person to record descriptions of the King Island emu from the wild.[18] At one point, Péron and some of his companions became stranded due to storms and took refuge with some sealers. They were served emu meat, which Péron described in favourable terms as tasting halfway "between that of the turkey-cock and that of the young pig".[4]

Péron did not report seeing any emus on the island himself, which might explain why he described them as being the size of mainland birds. Instead, most of what is known about the King Island emu today stems from a 33-point

wombats.[29] Péron's questionnaire remained unpublished until 1899, and very little was therefore known about the bird in life until then.[4]

Transported specimens

Royal Zoological Museum, Florence
, with reconstructed bones

Several emu specimens belonging to the different subspecies were sent to France, both live and dead, as part of the expedition. Some of these exist in European museums today. Le Naturaliste brought one live specimen and one skin of the mainland emu to France in June 1803. Le Géographe collected emus from both King and Kangaroo Island, and at least two live King Island individuals, assumed to be a male and female by some sources, were taken to France in March 1804. This ship also brought skins of five juveniles collected from different islands. Two of these skins, of which the provenance is unknown, are presently kept in Paris and Turin; the rest are lost.[13] In addition to rats, cockroaches, and other inconveniences aboard the ships, the emus were incommoded by the rough weather which caused the ships to shake violently; some died as a result, while others had to be force fed so they did not starve to death. In all, Le Géographe brought 73 live animals of various species back to France.[28]

The two individuals brought to France were first kept in captivity in the menagerie of

Jardin des Plantes after a year.[4] The "female" died in April 1822, and its skin is now mounted in the Muséum national d'Histoire naturelle of Paris. The "male" died in May 1822, and is preserved as a skeleton in the same museum.[13] A feather of the Paris skin was given to the Tasmanian Museum and Art Gallery, the only confirmed feather belonging to this subspecies currently in Australia.[28] The Paris skin contains several bones, but not the pelvis, which is an indicator of sex, so the supposed female identity is unconfirmed. Péron noted that the small emus brought to France were distinct from those of the mainland, but not that they were distinct from each other, or which island each had come from, so their provenance was unknown for more than a century later.[4]

There is also a skeleton in the

Liverpool Museum, but it may simply be a juvenile mainland emu.[13] Apart from the King Island emu specimens brought to France, a few are also known to have been brought to mainland Australia in 1803, but their fate is unknown.[4]

Contemporary depictions

1807 plate by Lesueur (left), perhaps showing this emu in the lower right, below a possible Kangaroo Island emu, as well as preparatory sketches for the illustration (right)

Péron's 1807, three-volume account of the expedition, Voyage de découverte aux terres Australes, contains an illustration (plate 36) of "casoars" by

Charles-Alexandre Lesueur, who was the resident artist during Baudin's voyage. The caption states the birds shown are from "Ile Decrès", the French name for Kangaroo Island, but there is confusion over what is actually depicted.[13] The two adult birds are labelled as a male and female of the same species, surrounded by juveniles. The family-group shown is improbable, since breeding pairs of the mainland emu split up once the male begins incubating the eggs. Lesueur's preparatory sketches also indicate these may have been drawn after the captive birds in Jardin des Plantes, and not wild ones, which would have been harder to observe for extended periods.[4]

Pfennigwerth has instead proposed that the larger, light-ruffed "male" was actually drawn after a captive Kangaroo Island emu, that the smaller, dark "female" is a captive King Island emu, that the scenario is fictitious, and the sexes of the birds indeterminable. They may instead only have been assumed to be male and female of the same species due to their difference in size. A crooked claw on the "male" has also been interpreted as evidence that it had lived in captivity, and it may also indicate that the depicted specimen is identical to the Kangaroo Island emu skeleton in Paris, which has a deformed toe. The juvenile on the right may have been based on the Paris skin of an approximately five-month-old emu specimen (from either King or Kangaroo Island), which may in turn be the individual that died on board le Geographe during rough weather, and was presumably stuffed there by Lesueur himself. The chicks may instead simply have been based on those of mainland emus, as none are known to have been collected.[4][6]

Extinction

elephant seals and sealers
(middle left) on King Island

The exact cause for the extinction of the King Island emu is unknown. Soon after the bird was discovered, sealers settled on the island because of the abundance of

elephant seals. Péron's interview with Cooper suggested that they likely contributed to the demise of the bird by hunting it, and perhaps by starting fires. Péron described how dogs were purpose-trained to hunt down the emus; Cooper even claimed to have killed no fewer than 300 emus himself.[18] Cooper had been on the island for six months, which suggests he killed 50 birds a month. His group of sealers consisted of eleven men as well as his wife, and they alone may have killed 3,600 emus by the time Péron visited them.[4]

Péron explained that the sealers consumed an enormous quantity of meat, and that their dogs killed several animals each day. He also observed such hunting dogs being released on Kangaroo Island, and mused that they might wipe out the entire population of kangaroos there in some years, but he did not express the same sentiment about the emus of King Island.

Natural fires may also have played a role.[13] It is probable that the two captive birds in France, which died in 1822, outlived their wild fellows on King Island, and were therefore the last of their kind.[2] Though Péron stated King Island "swarmed" with emus in 1802, they may have become extinct in the wild as early as 1805.[4] They were certainly extinct by 1836, when some English settlers arrived on the island. Elephant seals disappeared from the island around 1819 due to over-hunting.[6]

In 1967, when the King Island emu was still thought to be only known from prehistoric remains, the American ornithologist James Greenway questioned whether they could have been exterminated by a few natives, and speculated that fires started by prehistoric men or lightning may have been responsible. At this time, the mainland emu was also threatened by overhunting, and Greenway cautioned that it could end up sharing the fate of its island relatives if no measures were taken in time.[32]

References

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  6. ^ a b c d e f g Hume, J.; Steel, L.; Middleton, G.; Medlock, K. (2018). "In search of the dwarf emu: A palaeontological survey of King and Flinders Islands, Bass Strait, Australia". Contribuciones Científicas del Museo Argentino de Ciencias Naturales. 7: 81–98.
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  8. ^ Spencer, B. (1906). "The King Island Emu". The Victorian Naturalist. 23 (7): 139–140.
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  10. ^ a b c Rothschild, W. (1907). Extinct Birds. London: Hutchinson & Co. pp. 235–237.
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  15. ^ Jouanin, C. (1959). "Les emeus de l'expédition Baudin". L'Oiseau et la Revue Française d'Ornithologie (in French). 29: 168–201.
  16. ^ Balouet, J. C.; Jouanin, C. (1990). "Systématique et origine géographique de émeus récoltés par l'expédetion Baudin". L'Oiseau et la Revue Française d'Ornithologie (in French). 60: 314–318.
  17. ^ a b Parker, S. A. (1984). "The extinct Kangaroo Island Emu, a hitherto unrecognised species". Bulletin of the British Ornithologists' Club. 104: 19–22.
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  19. ^ Howard, R.; Moore, A. (2013). The Howard and Moore Complete Checklist of the Birds of the World, Volume 1: Non-passerines. Dickinson & Remsen. p. 6.
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  22. ^ a b c Geggel, L. (2021). "Huge egg from extinct dwarf emu found in sand dune". livescience.com. Retrieved 30 May 2021.
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