Overview

Brief Summary

Taxonomy

Elephantidae (the elephants) is the single family with living representatives in the mammal order Proboscidea. Wittemyer (2011) recognized three living elephant species: Asian Elephant (Elephas maximus), African Forest Elephant (Loxodonta cyclotis) and African Savanna Elephant (Loxodonta africana). However, Wittemyer notes that some authorities believe just a single African Elephant species should be recognized, with the forest and savanna forms recognized only as subspecies. African Savanna Elephants are the largest terrestrial animals on Earth.

Morphology

The most distinctive feature of elephantids and their extinct proboscidean relatives is the trunk, which is derived from the nose and upper lip. The African Elephant has two fingerlike projections at the end of its trunk whereas the Asian Elephant has just one. The trunk is very powerful, but also very sensitive and its opposable lips can grasp and manipulate very small items such as single nuts. In addition to manipulating objects, the trunk is also used for breathing, olfaction, touch, and sound production.

The ivory tusks of elephants are enlarged second incisors. Both male and female African Elephants have fully developed tusks, although tusk size varies geographically (in Asian Elephants, only males have fully developed tusks). In some areas, selection from hunting pressure by humans appears to have resulted in decreased average tusk size and an increase in the frequency of tusklessness.

The large ears of African Elephants play an important role in thermoregulation.

African and Asian Elephants differ in numerous ways, including body size, absolute and relative size and shape of ears, tusks, trunk structure, number of ribs, and number of toenails on the front and hind feet. In addition, relative to African Elephants, Asian Elephants tend to have smoother skin and more hair.

Behavior and Ecology

Elephants swim well and are able to submerge themselves and use the trunk as a breathing tube. Among the diverse communication modalities used by elephants is infrasonic communication, which elephants were discovered to utilize only in the late 20th century. The long wavelengths of infrasound are able to travel across large distances, with communication feasible across perhaps as much as 10 km under ideal conditions, although individuals can apparently be distinguished only up to one or a few kilometers. Evidence suggests that seismic signaling may also be used by elephants.

Elephants have a very complex social structure and young animals stay with their mother and her group for many years (perhaps for their entire lives). African Savanna Elephants typically stay within a few meters of their mothers for the first 4-8 years of life. Both Asian and African bulls are typically independent of their families by around 15 years (sometimes as young as six years).

Elephants spend as much as three quarters of their time feeding. Elephants both graze (feeding on grass) and browse (feeding  mainly on leaves and terminal twigs of woody plants) and the diet composition may shift dramatically between wet and dry seasons. Asian Elephant diets tend to include more grass than those of African Elephants.

Elephants can thrive in habitats ranging from deserts to rainforests. They play major roles in shaping ecosystems through their consumption of shrubs and trees and as seed dispersers.

In recent times, African Elephants have been distributed from southernmost South Africa to the Sahel. In Roman times, they were present even in the northern Mediterranean region. Today, most African Elephants live in the sub-Saharan savanna and dry woodland ecoregions, but they continue to persist in desert regions such as Mali's Sahel and the Namib. In addition, they are found in dense tropical forests such as those found on East Africa's volcanos. Historically, Asian Elephants occupied a broad range in tropical Asia from Iraq, India, and Sri Lanka to Malaysia, Indonesia, and southern China. Today, they have been extirpated from more than 85% of this range and over 60% of Asian Elephants are thought to reside in India. Other remnant populations are found in Sri Lanka, Burma, Thailand, and the larger islands of the Malay Archpelago.

Elephants and Humans

The lives of elephants and humans have been intertwined for millenia. Asian Elephants were domesticated in the third millenium BC in the Indus Valley and this likely drove the first major declines of the species. Ivory has been a major focus of human-elephant interactions for thousands of years. Given that only the males of Asian Elephants bear tusks, African ivory was needed to satisfy the demand in India, China, and Japan and was being traded by the 6th century BC. The African slave trade was closely tied to the ivory trade, with slaves carrying ivory to the coast, where both were sold. Elephants were eradicated from much of west and southern Africa during this period. With the decline of the slave trade, ivory trade also declined and elephant populations are thought to have rebounded during much of the 1900s. Unfortunately, the 1970s saw a huge upsurge in the ivory trade with a devastating impact. It has been estimated that between 1979 and 1989 the African Elephant population was reduced from around 1.3 million to around half a million. Since then, there have been periods of both recovery and decline and the status of African Elephants remains precarious. As large-scale agriculture has increased in Africa since the 1980s, human-elephant conflicts over crop-raiding have increased. Asian Elephant populations have continued to decline as a result of both the ivory trade and habitat loss/range reduction.  Although young elephants can fall prey to Tigers (in Asia) and Lions (in Africa), adult elephants are safe from predators except for humans.

At one time, elephants ranged over much of Africa and southern Asia and into the Middle East. Demand for ivory by the Roman Empire is thought to have led to the eradication of African Elephants from the northern Sahara and Asian Elephants from the Middle East. Elephant populations in both Africa and Asia declined with the increased demand for ivory (notably, for piano keys in the 1800s and 1900s). Range reduction and fragmentation poses a serious threat to the long-term viability of elephant populations in both Africa and Asia. From the vantage point of the early decades of the 21st century, only in southern Africa do elephant populations appear relatively secure, but elephants have shown themselves to be highly adapable and with adequate protection there is still hope for recovery over much of their current range. If the ivory trade increases, this will pose a great threat to remaining elephant populations, especially in light of the political instability in many of the countries in which elephants persist. Counterbalancing these threats, however, is the growing economic importance of ecotourism in many countries with elephants.

(Wittemeyer 2011 and references therein)

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Comprehensive Description

Elephants have the largest cerebral cortex of all terrestrial animals.

  • Hart BL, Hart LA, McCoy M, Sarath CR. Cognitive behavior in Asian elephants: use and modification of branches for fly switching. Anim Behav 62: 839–847, 2001.
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Evolution and Systematics

Functional Adaptations

Functional adaptation

Large ears aid cooling: elephant
 

The large ears of elephants aid cooling by radiating heat from blood vessels, and flapping to generate cooling air currents.

     
  "Elephants, too, have huge ears relative to body size, and they are also used for temperature regulation. It has been shown that blood passing through the ears of an African elephant may lose as much as 9˚C of heat, a valuable cooling device in the hot African summer. To increase the effect, elephants spray their ears with water, and flap them to create cooling air currents." (Foy and Oxford Scientific Films 1982:170)
  Learn more about this functional adaptation.
  • Foy, Sally; Oxford Scientific Films. 1982. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London. 238 p.
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Functional adaptation

Vibrations alert others to danger: elephants
 

Elephants alert others to danger with low-frequency vibrations created by stomping their feet.

   
  "Thus, if an elephant is alarmed or disturbed by something, it stomps the ground in order to alert others to the danger. The vibrations produced by its feet travel rapidly through the ground and are sensed through the feet of other elephants as far away as 31 miles (50 km)." (Shuker 2001:36)
  Learn more about this functional adaptation.
  • Shuker, KPN. 2001. The Hidden Powers of Animals: Uncovering the Secrets of Nature. London: Marshall Editions Ltd. 240 p.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records:50
Specimens with Sequences:71
Specimens with Barcodes:47
Species:8
Species With Barcodes:8
Public Records:35
Public Species:6
Public BINs:6
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Barcode data

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Wikipedia

Mammuthus rumanus

Mammmuthus rumanus is a species of mammoth that lived during the Pliocene what is today the Eastern Europe. Fossil remains have been found in the United Kingdom and Romania.[1][2]

Evolution[edit]

Recent revalidation of the species Mammuthus rumanus influences several interrelated aspects of mammoth evolution. European material referred to M. rumanus might provide a useful background for the identification of finds from Africa and the Middle East. It seems plausible that M. rumanus originated in Africa c. 3.5 Ma and migrated to Eurasia via the Levant. While remaining poorly known, M. rumanus apparently played a significant role in the dispersal of mammoths to Eurasia, and any additional information on that species might elucidate problems of the earlier stages of mammoth evolution in Africa and their subsequent dispersal.[3]

References[edit]

  1. ^ Adrian M. Lister, Victoria L. Herridge (9 May 2012). "Extreme insular dwarfism evolved in a mammoth". Proc. R. Soc. B. doi:10.1098/rspb.2012.0671. Retrieved 17 November 2013. 
  2. ^ Adrian M. Lister, Victoria L. Herridge (2004). "The earliest mammoths in Europe". 18th International Senckenberg Conference. 
  3. ^ Markov, Georgi N. (25 October 2012). "Mammuthus rumanus, early mammoths, and migration out of Africa: Some interrelated problems". Quaternary International. 276–277: 23–26. 
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Elephantidae

The Elephantidae are a taxonomic family, collectively elephants and mammoths. These are terrestrial large mammals with a trunk and tusks. Most genera and species in the family are extinct. Only two genera, Loxodonta (African elephants) and Elephas (Asiatic elephants), are living.

The family was first described by John Edward Gray in 1821, and later assigned to taxonomic ranks within the order Proboscidea. Elephantidae have also been revised by various authors to include or exclude other extinct proboscidean genera.

Contents

Classification

"Man, and the elephant" Plate from Hawkins A comparative view of the human and animal frame, 1860

The family diverged from a common ancestor of the Mammutidae, which includes species termed as mastodons. The author of Mammutidae also published Gomphotheriidae, more closely related to Elephantidae, which also includes species previously described as Mastodon. The classification of proboscideans is unstable and frequently revised, some relationships within the order remain unclear, and it is incompletely summarised as:[1]

The most accurate phylogenetic tree of the elephants and mammoths as of 2010
Elephantimorpha (Proboscidea)
Elephantida
Elephantidae (elephants and mammoths)
Primelephas
Loxodonta
Elephas
Mammuthus
Palaeoloxodon
Stegodon
Stegolophodon
Stegotetrabelodon
Stegodibelodon
Gomphotheriidae (Gomphothere)
Mammutida
Mammutidae (mastodons)
Mammut
Zygolophodon
incertae sedis
Eritreum

The genera †Anancus, †Tetralophodon, †Stegomastodon, †Paratetralophodon and †Cuvieronius are placed by some authors within the Elephantidae, while others give a treatment as Gomphotheriidae. Similarly, Stegodon and Stegolophodon have sometimes been placed in Stegodontidae. The systematics of the living subspecies and species, the modern elephants, has undergone several revisions. A list of extant Elephantidae, excluding the extinct species of the two genera, includes:[2]

Elephantidae
Elephas (Asiatic)
E. maximus Asian elephant
E. m. maximus Sri Lankan elephant
E. m. borneensis Borneo elephant
E. m. indicus Indian elephant
E. m. sumatranus Sumatran elephant
Loxodonta (African)
L. africana African bush elephant
L. cyclotis African forest elephant

Scientific classification of Elephantidae taxa embraces an extensive record of fossil specimens, over millions of years, some of which existed until the end of the last ice age. Some species were extirpated more recently. The discovery of new specimens and proposed cladistics have resulted in systematic revisions of the family and related proboscideans.

Elephantidae are classified informally as the elephant family, or in a paleobiological context as elephants and mammoths. The common name elephant primarily refers to the living taxa, the modern elephants, but may also refer to a variety of extinct species, in this family and others (see Elephant (disambiguation)). Other members of Elaphantidae, especially members of Mammuthus, are referred to by the common name mammoth.

Evolutionary history

Evolution of elephants from the ancient Eocene (bottom) to the modern day (top)

Although the fossil evidence is uncertain, by comparing genes, scientists discovered evidence that Elephantidae and other proboscideans share a distant ancestry with Sirenia (sea cows) and Hyracoidea (hyraxes).[3] These have been assigned with the demostylians to the clade Paenungulata. In the distant past, members of the hyrax family grew to large sizes, and the common ancestor of all three modern families likely was some kind of amphibious hyracoid.[citation needed] One hypothesis is these animals spent most of their time under water, using their trunks like snorkels for breathing.[4][5] Modern elephants have this ability and are known to swim in that manner for up to six hours and 50 km (31 mi).

In the past, a much wider variety of genera and species were found, including the mammoths and stegodons.[6][7]

See also

References

  1. ^ Classification of the Elephantidae Paleobiology Database Accessed: August 2009
  2. ^ Shoshani, J. (2005). "Order Proboscidea". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. ISBN 978-0-8018-8221-0. OCLC 62265494. http://www.bucknell.edu/msw3/browse.asp?id=11500002.
  3. ^ Ozawa, Tomowo; Seiji Hayashi, Victor M. Mikhelson (1997-04-24), "Phylogenetic Position of Mammoth and Steller's Sea Cow Within Tethytheria Demonstrated by Mitochondrial DNA Sequences", Journal of Molecular Evolution 44 (4): 406–413, doi:10.1007/PL00006160, PMID 9089080
  4. ^ West, John B. (2001), "Snorkel breathing in the elephant explains the unique anatomy of its pleura", Respiratory Physiology 126 (1): 1–8, doi:10.1016/S0034-5687(01)00203-1, PMID 11311306
  5. ^ West, John B.; Fu, Zhenxing; Gaeth, Ann P.; Short, Roger V. (2003-11-14), "Fetal lung development in the elephant reflects the adaptations required for snorkeling in adult life", Respiratory Physiology & Neurobiology 138 (2-3): 325–333, doi:10.1016/S1569-9048(03)00199-X, http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6X16-49MF0FR-2-7&_cdi=7234&_user=10&_orig=article&_coverDate=11%2F14%2F2003&_sk=998619997&view=c&wchp=dGLbVzb-zSkWA&md5=ad91a1eea54ef52d0a723aeec5232049&ie=/sdarticle.pdf
  6. ^ Todd, N. E. (2001). African Elephas recki: time, space and taxonomy (pdf). In: Cavarretta, G., P. Gioia, M. Mussi, and M. R. Palombo. The World of Elephants, Proceedings of the 1st International Congress. Consiglio Nazionale delle Ricerche. Rome, Italy.
  7. ^ Todd, N. E. (2005). Reanalysis of African Elephas recki: implications for time, space and taxonomy. Quaternary International 126-128:65-72.
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