Megafauna


Megafauna
The African bush elephant, Earth's largest living land animal

In terrestrial zoology, megafauna (Ancient Greek megas "large" + New Latin fauna "animal") are "giant", "very large" or "large" animals. The most common thresholds used are 44 kilograms (100 lb)[1][2] or 100 kilograms (220 lb).[2][3] This thus includes many species not popularly thought of as overly large, such as white-tailed deer and red kangaroo, and for the lower figure, even humans.

In practice the most common usage encountered in academic and popular writing describes land animals roughly larger than a human which are not (solely) domesticated. The term is especially associated with the Pleistocene megafauna — the giant and very large land animals considered archetypical of the last ice age such as mammoths.[4] It is also commonly used for the largest extant wild land animals, especially elephants, giraffes, hippopotamuses, rhinoceroses, elk, condors, etc. Megafauna may be subcategorized by their trophic position into megaherbivores (e.g. elk), megacarnivores (e.g. lions), and more rarely, megaomnivores (e.g. bears).

Other common uses are for giant aquatic species, especially whales, any larger wild or domesticated land animals such as larger antelope and cattle, and dinosaurs and other extinct giant reptilians.

The term is also sometimes applied to animals (usually extinct) of great size relative to a more common or surviving type of the animal, for example the 1 m (3 ft) dragonflies of the Carboniferous period.

Contents

Ecological strategy

Megafauna — in the sense of the largest mammals and birds — are generally K-strategists, with great longevity, slow population growth rates, low death rates, and few or no natural predators capable of killing adults. These characteristics, although not exclusive to such megafauna, make them highly vulnerable to human overexploitation.

Mass extinctions

A well-known mass extinction of megafauna, the Holocene extinction (see also Quaternary extinction event), occurred at the end of the last ice age glacial period (a.k.a. the Würm glaciation) and wiped out many giant ice age animals, such as woolly mammoths, in the Americas and northern Eurasia. Various theories have attributed the wave of extinctions to human hunting, climate change, disease, a putative extraterrestrial impact, or other causes. However, this extinction pulse near the end of the Pleistocene was just one of a series of megafaunal extinction pulses that have occurred during the last 50,000 years over much of the Earth's surface, with Africa and southern Asia being largely spared. (The latter areas did suffer a gradual attrition of megafauna, particularly of the slower-moving species, over the last several million years.[5][6]) Outside the mainland of Afro-Eurasia, these megafaunal extinctions followed a distinctive landmass-by-landmass pattern that closely parallels the spread of humans into previously uninhabited regions of the world, and which shows no correlation with climate.[7][8] Australia was struck first around 46,000 years ago,[9] followed by Tasmania about 41,000 years ago (after formation of a land bridge to Australia about 43,000 years ago),[10][11][12] Japan apparently about 30,000 years ago,[13] North America 13,000 years ago, South America about 500 years later,[14][15] Cyprus 10,000 years ago,[16][17] the Antilles 6000 years ago,[18] New Caledonia[19] and nearby islands[20] 3000 years ago, Madagascar 2000 years ago,[21] New Zealand 700 years ago,[22] the Mascarenes 400 years ago,[23] and the Commander Islands 250 years ago.[24] Nearly all of the world's isolated islands could furnish similar examples of extinctions occurring shortly after the arrival of Homo sapiens, though most of these islands, such as the Hawaiian Islands, never had terrestrial megafauna, so their extinct fauna were smaller.[7][8]

Continuing human hunting and environmental disturbance has led to additional megafaunal extinctions in the recent past, and has created a serious danger of further extinctions in the near future (see examples below).

A number of other mass extinctions occurred earlier in Earth's geologic history, in which some or all of the megafauna of the time also died out. Famously, in the Cretaceous–Tertiary extinction event the dinosaurs and most other giant reptilians were eliminated. However, the earlier mass extinctions were more global and not so selective for megafauna; i.e., many species of other types, including plants, marine invertebrates[25] and plankton, went extinct as well. Thus, the earlier events must have been caused by more generalized types of disturbances to the biosphere.

Effect of megafaunal extinctions on methane emissions

Many herbivores produce methane as a byproduct of foregut fermentation in digestion, and release it through belching. Large populations of herbivore megafauna have the potential to contribute greatly to the atmospheric concentration of methane, which is an important greenhouse gas. Today, around 20% of annual methane emissions come from livestock methane release. Recent studies have indicated that the extinction of megafaunal herbivores may have caused a reduction in atmospheric methane. This hypothesis is relatively new.[26]

Several studies have examined the effect of elimination of megaherbivorous mammals on methane emissions. One study examined the methane emissions from the bison that occupied the Great Plains of North America before contact with European settlers. The study estimated that the removal of the bison caused a decrease of 2.2 Tg/yr. This is a proportionally large change for the time period.[27]

Another study examined the change of methane concentration in the atmosphere at the end of the Pleistocene epoch after the extinction of megafauna in the Americas. After early humans migrated to the Americas ~13,000 BP, their hunting and other associated ecological impacts led to the extinction of many megafaunal species in the region. Calculations suggest that this extinction decreased methane production by ~9.6 Tg/yr. Ice core records support this hypothesis of rapid methane decrease during the time period. This suggests that the absence of megafaunal methane emissions may have contributed to the abrupt climatic cooling at the onset of the Younger Dryas.[26]

Examples

The following are some notable examples of animals often considered as megafauna (in the sense of the "large animal" definition). This list is not intended to be exhaustive:

Gallery

Extinct

Living

See also

References

  1. ^ a b c Stuart, A. J. (1991-11). "Mammalian extinctions in the Late Pleistocene of northern Eurasia and North America". Biological Reviews (Wiley) 66 (4): 453–562. doi:10.1111/j.1469-185X.1991.tb01149.x. 
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  18. ^ Steadman, D. W.; Martin, P. S.; MacPhee, R. D. E.; Jull, A. J. T.; McDonald, H. G.; Woods, C. A.; Iturralde-Vinent, M.; Hodgins, G. W. L. (2005-08-16). "Asynchronous extinction of late Quaternary sloths on continents and islands". Proc. Natl. Acad. Sci. USA (National Academy of Sciences) 102 (33): 11763–11768. doi:10.1073/pnas.0502777102. PMC 1187974. PMID 16085711. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1187974. 
  19. ^ Anderson, A.; Sand, C.; Petchey, F.; Worthy, T. H. (2010). "Faunal extinction and human habitation in New Caledonia: Initial results and implications of new research at the Pindai Caves". Journal of Pacific Archaeology 1 (1): 89–109. hdl:10289/5404. 
  20. ^ White, A. W.; Worthy, T. H.; Hawkins, S.; Bedford, S.; Spriggs, M. (2010-08-16). "Megafaunal meiolaniid horned turtles survived until early human settlement in Vanuatu, Southwest Pacific". Proc. Natl. Acad. Sci. USA 107 (35): 15512–15516. doi:10.1073/pnas.1005780107. 
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Look at other dictionaries:

  • Megafauna — Megafauna,   Bodenbiologie: die tierischen Bodenorganismen, die größer als 20 mm sind; z. B. Schnecken, Regenwürmer, große Gliederfüßer und Wirbeltiere, die ganz oder teilweise im Boden leben (u. a. Maulwürfe …   Universal-Lexikon

  • Megafauna — Beutellöwen Skelett im Naracoorte Caves Nationalpark, South Australia. Als Megafauna bezeichnet man den Anteil der Tiere, der in einem Habitat die körperlich größten Organismen stellt. Diese Einteilung ist willkürlich, hält sich aber an allgemein …   Deutsch Wikipedia

  • Megafauna — Este artículo o sección necesita referencias que aparezcan en una publicación acreditada, como revistas especializadas, monografías, prensa diaria o páginas de Internet fidedignas. Puedes añadirlas así o avisar al autor pri …   Wikipedia Español

  • megafauna — /meg euh faw neuh/, n. Ecol. land animals of a given area that can be seen with the unaided eye. [MEGA + FAUNA] * * * ▪ biology       in soil science, animals such as earthworms and small vertebrates (e.g., moles, mice, hares, rabbits, gophers,… …   Universalium

  • megafauna — very large animals, mostly whales in water but conceivably some of the larger fishes could be included. See also charismatic megafauna …   Dictionary of ichthyology

  • Megafauna — (Del griego Mega, grande) Megafauna, término que en Paleontología se designa a los grandes animales terrestres en particular mamíferos que se extinguieron entre fines del Pleistoceno y comienzos del Holoceno (12.000 a.C 8.000 a. C) en diferentes… …   Enciclopedia Universal

  • megafauna — noun Date: 1927 1. animals (as bears, bison, or mammoths) of particularly large size 2. fauna consisting of individuals large enough to be visible to the naked eye • megafaunal adjective …   New Collegiate Dictionary

  • megafauna — noun a) The large animals of a given region or time, considered as a group. b) A treatise on such a group of large animals …   Wiktionary

  • Megafauna — Me|ga|fau|na die; <zu ↑mega...> Bez. für die tierischen Bodenorganismen, die größer als 20 mm sind (z. B. Schnecken, Regenwürmer, Maulwürfe; Biol.) …   Das große Fremdwörterbuch

  • megafauna — n. larger fauna of a particular region …   English contemporary dictionary


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