Elephant bird

Elephant birds
Fossil range: Quaternary–present
↓
Aepyornis maximus skeleton and egg
Conservation status

Extinct (IUCN 3.1)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Superorder: Paleognathae
Order: Aepyornithiformes
A. Newton, 1884[1]
Family: †Aepyornithidae
(Bonaparte, 1853)[1]
Genera

†Aepyornis
†Mullerornis
Diversity
2 genera, 7 species

Elephant birds are an extinct family of flightless birds found only on the island of Madagascar and comprising the genera Aepyornis and Mullerornis.

Contents

Description

Size of Aepyornis maximus (purple) compared to a human, an ostrich, and some non-avian theropod dinosaurs

The elephant birds, which were giant ratites native to Madagascar, have been extinct since at least the 17th century. Étienne de Flacourt, a French governor of Madagascar in the 1640s and 1650s, recorded frequent sightings of elephant birds. Aepyornis was the world's largest bird, believed to have been over 3 metres (10 ft) tall and weighing close to 400 kg (880 lb).[2] Remains of Aepyornis adults and eggs have been found; in some cases the eggs have a circumference of over 1 metre (3 ft) and a length up to 34 centimetres (13 in).[3] The egg volume is about 160 times greater than a chicken egg.[4]

Species

Four species are usually accepted in the genus Aepyornis today; A. hildebrandti, A. gracilis, A. medius and A. maximus,[5] but the validity of some is disputed, with numerous authors treating them all in just one species, A. maximus. Up to three species are also generally included in Mullerornis.[2]

Genus Aepyornis

Genus Mullerornis

Food

Because there is no rainforest fossil record in Madagascar, it is not known for certain if there were species adapted to dense forest dwelling, like the cassowary in Australia and New Guinea today. However, some rainforest fruits with thick, highly sculptured endocarps, such as that of the currently undispersed and highly threatened forest coconut palm Voanioala gerardii, may have been adapted for passage through ratite guts, and the fruit of some palm species are indeed dark bluish purple (e.g. Ravenea louvelii and Satranala decussilvae), just like many cassowary-dispersed fruits.[8]

Biogeography

Front view of an Aepyornis skeleton

Like the cassowary, ostrich, rhea, emu and kiwi, Mullerornis and Aepyornis were ratites; they could not fly, and their breast bones had no keel. Because Madagascar and Africa separated too long ago for the ratite lineage,[9] Aepyornis had been thought to have dispersed and become flightless and gigantic in situ.[10] A land bridge from elsewhere in Gondwana to Madagascar for the elephant bird-ostrich lineage was probably available around 85 million years ago.[11] However, subfossil Aepyornis fragments have not yet been successfully sequenced for mitochondrial DNA.[12] Some DNA have been extracted.[13][14]

Aepyornis maximus restoration

Supposed remains of "aepyornithid" eggs found on the eastern Canary Islands represent a major biogeographical enigma. These islands were probably not connected to mainland Africa when elephant birds were alive. During episodes of very low sea levels, there may have been a land bridge, and at least for some time, there probably was an archipelago between Fuerteventura/Lanzarote and the African coast. This would have enabled flightless birds to cross over to these islands by chance. Still, there is no indication that elephant birds evolved outside Madagascar, and today, the Canary Island eggshells are considered to belong to extinct North African birds that may or may not have been ratites (Eremopezus/Psammornis), or even Pelagornithidae, prehistoric seabirds of immense size.

Extinction

It is often believed that the extinction of the Aepyornis was an effect of human activity. However, the birds were probably not only elusive but widespread, occurring from the northern to the southern tip of Madagascar,[4] yet their eggs were vulnerable. A recent archaeological study found remains of eggshells among the remains of human fires,[15] suggesting that the eggs regularly provided meals for entire families, but it is not known if there were taboos ("fady") against the killing of adult birds, although there is indeed evidence that they were killed. Animals arriving with the human colonists, such as rats and dogs, may also have preyed upon the eggs of the ratite population and reduced their viability.

The exact time period when they died out is also not certain; tales of these giant birds may have persisted for centuries in folk memory. There is archaeological evidence of Aepyornis from a radiocarbon-dated bone at 1880 +/- 70 BP (= c. 120 AD) with signs of butchering, and on the basis of radiocarbon dating of shells, about 1000 BP (= c. 1000 AD).[4]

An alternative theory states that humans hunted the elephant birds to extinction in a very short time for such a large landmass (the blitzkrieg hypothesis) or is the possible secondary effect of human impact by possible transfer of hyperdiseases from human commensals such as chickens and guineafowl. The bones of these domesticated fowl have been found in subfossil sites in the island (MacPhee and Marx, 1997: 188), such as Ambolisatra (Madagascar), where Mullerornis sp. and Aepyornis maximus have been reported.[16] Also reported by these authors, ratite remains have been found in W-SW Madagascar, at Belo-sur-Mer (A. medius, Mullerornis rudis), Bemafandry (M. agilis) and Lamboharana (Mullerornis sp.).

A third viable theory to explain the demise of the giant elephant birds, as apparently first pointed by Sir David Attenborough, is climate change, related to an increased drying of Madagascar during the Holocene (to which the impact of humans might have been additive).[17]

Aepyornis skull

Name

English name

Aepyornis maximus is commonly known as the 'elephant bird', a term that apparently originated from Marco Polo's account of the rukh in 1298, although he was apparently referring to an eagle-like bird strong enough to "seize an elephant with its talons".[15] Sightings of eggs of elephant birds by early sailors (e.g. text on the Fra Mauro map of 1467-69, if not attributable to ostriches) could also have been erroneously attributed to a giant raptor from Madagascar. The legend of the roc could also have originated from sightings of such a giant subfossil eagle related to the African Crowned Eagle, which has been described in the genus Stephanoaetus from Madagascar,[18] being large enough to carry off large primates; today, lemurs still retain a fear of aerial predators such as these. Another might be the perception of ratites retaining neotenic features and thus being mistaken for enormous chicks of a presumably more massive bird.

Malagasy name

The ancient Malagasy name for the bird is Vorompatra, meaning "bird of the Ampatres". The Ampatres are today known as the Androy region of southern Madagascar.[15] Indeed, Étienne de Flacourt wrote (1658), "vouropatra - a large bird which haunts the Ampatres and lays eggs like the ostriches; so that the people of these places may not take it, it seeks the most lonely places".

Eggs

Aepyornis eggs, Muséum national d'Histoire naturelle, Paris
Elephant bird egg, Hungarian Natural History Museum.

Occasionally the subfossilized eggs are found intact[19]. The National Geographic Society in Washington holds a specimen of an Aepyornis egg which was given to Luis Marden in 1967. The specimen is intact and contains an embryonic skeleton of the unborn bird. Another giant Aepyornis egg is on display at the Harvard Museum of Natural History in Cambridge, MA. A cast of the 'Aepyornis' egg is preserved at the Grant Museum of Zoology at London University, and has been adopted by Claudia, the niece of the author and illustrator Charlotte Cory. The BBC television personality David Attenborough owns an almost complete fossilized eggshell, which he pieced together from fragments he collected on a visit to Madagascar. There is also an intact specimen of an Elephant Bird's egg (contrasted with the eggs from other bird species, including a Hummingbird's egg) on display at the Delaware Museum of Natural History, just outside Wilmington, Delaware, USA, and another in the Natural History Museum, London, England.

In Art and Literature

Restoration of Aepyornis maximus

See also

Notes

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Brands, S. (2008)
  2. ↑ 2.0 2.1 2.2 Davies, S. J. J. F. (2003)
  3. ↑ Mlíkovsky, J. (2003)
  4. ↑ 4.0 4.1 4.2 Hawkins, A. F. A. & Goodman, S. M. (2003)
  5. ↑ Brodkorb, P. (1963)
  6. ↑ 6.0 6.1 6.2 Brands (a), S. (2008)
  7. ↑ LePage, D. (2008)
  8. ↑ Dransfield, J. & Beentje, H. (1995)
  9. ↑ Yoder, A. D. & Nowak, M. D. (2006)
  10. ↑ van Tuinen, M. et al. (1998)
  11. ↑ Hay, W. W., et al. (1999)
  12. ↑ Cooper, A., et al. (2001)
  13. ↑ International Darwin Bicentennial Symposium Ancient DNA
  14. ↑ Extinct giant bird DNA recovered from fossil eggs
  15. ↑ 15.0 15.1 15.2 Pearson and Godden (2002)
  16. ↑ Goodman, S. M. & Rakotozafy, L. M. A. (1997)
  17. ↑ Attenborough, D. (1961)
  18. ↑ Goodman, S. M. (1994)
  19. ↑ BBC News

References

External links