Elefante

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Elefantes
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Arbusto africano elefante (Loxodonta africana)
Clasificación científica
Reino: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Clase: Mammalia
Superorden: Afrotheria
Orden: Proboscidea
Familia: Elephantidae
Gray , 1821
Genera

Loxodonta
Elephas

Los elefantes son los grandes mamíferos de la familia Elephantidae y el orden Proboscidea . Están representados por tres especies existentes: el elefante africano de Bush (Loxodonta africana), el elefante de bosque africano (L. cyclotis) y el elefante asiático (Elephas maximus). Las dos especies africanas fueron consideradas tradicionalmente como dos subespecies diferentes, en la misma especie. Estas tres especies se encuentran dispersas en el África subsahariana y el sur de Asia sudoriental . Ellos son los únicos supervivientes proboscidios, aunque varias especies extintas han sido identificados, incluidos los parientes cercanos de los elefantes, los mamuts . Los elefantes son los animales terrestres más grandes de la vida. Hombre elefante africano arbusto puede alcanzar una altura de 3,20 a 4 m (10,5 a 13,1 pies) y un peso de 4,700-6,048 kg (10,362-13,334 lb). Los animales tienen varias características distintivas, incluyendo una larga probóscide o el tronco que utilizan para numerosos fines, en particular para los objetos de agarre. Las aletas del oído son particularmente grandes y ayudan a controlar la temperatura de sus cuerpos masivos. Sus incisivos crecen en grandes colmillos, que sirven como herramientas para excavación y movimiento, así como armas para la lucha. Las especies africanas tienen grandes orejas y la espalda cóncava mientras que el elefante asiático tiene orejas más pequeñas y una espalda convexa.

Los elefantes son herbívoros y se pueden encontrar en numerosos hábitats, incluyendo sabanas , selvas , desiertos y pantanos , y prefieren permanecer cerca del agua. Los elefantes son considerados como especies clave , debido al impacto que tienen en sus entornos. Otros animales tienden a mantener su distancia, y los depredadores como leones , tigres , hienas salvajes y los perros por lo general sólo afectan a los terneros. La vida social de los elefantes pueden variar. Las hembras o vacas tienden a vivir en grupos familiares, que pueden constar de una sola hembra con sus crías o varias hembras relacionadas con descendencia. Este último son guiados por el más antiguo de vaca, conocida como la matriarca . Los elefantes parecen tener una sociedad fisión-fusión en la que varios grupos de la familia se reúnen para socializar. Los varones o toros abandonar sus grupos familiares cuando llegan a la pubertad, y puede vivir solo o con otros machos. Los toros adultos en su mayoría interactuar con grupos familiares en la búsqueda de un compañero. Bulls entrar en un estado de mayor testosterona y agresividad conocido como musth , que les ayuda a obtener el dominio y tener éxito reproductivo. Los terneros son el centro de atención en sus grupos familiares, y dependen de sus madres por hasta tres años. Los elefantes se comunican por tacto, la vista y el sonido. Se conoce el uso de infrasonidos y sísmica para comunicación a larga distancia.

Los elefantes son muy inteligentes, siendo comparable a los primates y cetáceos . Ellos parecen tener conciencia de sí mismo y mostrar empatía por morir o individuos muertos de su especie. Los elefantes africanos están juntos catalogado como vulnerable por la Unión Internacional para la Conservación de la Naturaleza (UICN), mientras que el elefante asiático se considera que está en peligro de extinción . Una de las mayores amenazas a las poblaciones de elefantes es el comercio de marfil , ya que los animales son cazados furtivamente por sus colmillos de marfil. Otras amenazas para los elefantes silvestres incluyen la destrucción del hábitat y los conflictos con la población local. Los elefantes son usados ??como animales de trabajo , tanto en Asia y África, y se emplean para un número de tareas. También han sido utilizados como instrumentos de guerra, y se han puesto en exhibición en zoos y circos . Fácilmente reconocible, los elefantes han jugado un papel importante en las culturas humanas, y se han destacado en el arte, el folklore, la religión, la literatura y la cultura popular .

Contenido

Etimología

La palabra "elefante" se basa en el latín "Elephantus" ("elefante"), que a su vez deriva de los griegos (?????? elephas), una palabra posiblemente fenicio origen. [1] Homer utilizado la palabra griega que significa marfil , pero desde el momento de Herodoto , la palabra se refirió también al animal. [2] La palabra "elefante" en Inglés medio como "olifaunt" y fue tomado de francés medieval "olifante". Loxodonta , el nombre del género para la Los elefantes africanos, en griego significa "cara oblicua diente". [3]

Taxonomía

Clasificación, especies y subespecies

Elefante asiático (Elephas maximus)
Elefante africano del bosque (Loxodonta cyclotis)

Los tres se conservan especies-el elefante elefante africano de Bush (Loxodonta africana), el elefante de bosque africano (L. cyclotis) y el elefante asiático ( Elephas maximus), todos pertenecen a la familia Elephantidae y el orden Proboscidea . Sus más cercanos existentes parientes son los sirenios ( dugongos y manatíes ) y los hyraxes , con los que comparten el clado Paenungulata dentro del superorden Afrotheria . [4] Los elefantes y los sirenios son más Classifed en el clado Tethytheria . [5] En conjunto, el elefante de tres especies habitan en el África subsahariana y el sur de Asia sudoriental . Las dos especies africanas tienen grandes orejas, la espalda cóncava, la piel más arrugada y dos dedos como extensiones en la punta de la trompa. El elefante asiático tiene orejas más pequeñas, una espalda convexa, lisa la piel, y una extensión en la punta del tronco. [6] En los elefantes africanos, las crestas de los dientes molares están en forma de rombo, mientras que los del elefante asiático son bucle en forma. [7] Además, el elefante asiático tiene dorsales golpes en la cabeza [6] y algunas manchas de despigmentación. [8] Diferencias respecto de si la extinta Mammuthus estaba más estrechamente relacionado con Loxodonta o Elephas. Algunos estudios de ADN sugieren Mammuthus está más relacionada con la primera, [9] [10] mientras que otros sugieren que el segundo. [11] [12] [5] Las comparaciones morfológicas sugieren Mammuthus y Elephas son taxones hermanos, mientras que la comparación de la proteína albúmina y colágeno sugieren que los tres géneros son igualmente relacionados entre sí. [13] Algunos científicos creen que un clonado de mamut embrión podría desarrollarse en el vientre de un elefante asiático. [14]

Carl Linnaeus primero describe los Elephas género y un elefante de Sri Lanka (entonces conocida como Ceilán) bajo el binomio Elephas Maximus en 1758. En 1798, Georges Cuvier primero en describir el elefante indio bajo el binomio Elephas indicus. Zoólogo holandés Jacob Temminck Coenraad primero en describir el elefante de Sumatra en 1847 bajo el binomio sumatranus Elephas. Inglés zoólogo Frederick Nutter Chasen clasificarse los tres como subespecie del elefante asiático en 1940. [15] elefantes asiáticos variar geográficamente en el color y la cantidad de despigmentación. El elefante de Sri Lanka (Elephas maximus maximus) vive en Sri Lanka, el elefante indio (E. m. indicus) es nativa de Asia continental (en el subcontinente indio y de Indochina ), y el elefante de Sumatra (E. m. sumatranus) es hallado en Sumatra. [6] Una subespecie en disputa, el elefante de Borneo , vive en el norte de Borneo y es más pequeño que las otras subespecies, pero con grandes orejas, una cola más larga, y los colmillos rectos. Fue descrito por Sri Lanka zoólogo Paules Edward Pieris Deraniyagala en 1950 bajo el trinomio borneensis Elephas maximus en 1950, tomando como tipo de una ilustración en la revista National Geographic . [16] Fue posteriormente subsumido bajo cualquiera E. m. indicus o E. m. sumatranus. Los resultados de un 2003 análisis genético indicar sus antepasados ??separados de la población continental alrededor de 300.000 años atrás. [17] Un estudio de 2008 encontró que los elefantes de Borneo no son nativos de la isla, pero que llevados por el Sultán de Sulu de Java , donde los elefantes son ahora extinto. [16]

Las especies africanas fueron clasificadas históricamente como una de las especies, el elefante africano. El elefante africano se clasificó por primera vez por el naturalista alemán Johann Friedrich Blumenbach en 1797 como Elephas africana. [18] El género Loxodonta se creía comúnmente que han sido nombrados por Georges Cuvier en 1825. Sin embargo, Cuvier deletreó Loxodonte. Un autor anónimo romanizado la ortografía de Loxodonta y el Código Internacional de Nomenclatura Zoológica reconoce como la autoridad competente. [19] En 1942, 18 subespecies de elefante africano fueron reconocidos por Henry Fairfield Osborn , pero nuevos datos morfológicos disminuido el número de subespecies clasificados , [20] y por la década de 1990, sólo dos fueron reconocidos, el elefante Bush (L. Una africana.) y el elefante de bosque (L. un cyclotis.), [21] éste tiene las orejas pequeñas y redondeadas más y más delgadas y recta colmillos, y se limita a las zonas boscosas de occidental y África central . [22] Un estudio de 2000 abogó por la elevación de las dos formas en especies separadas basadas en las diferencias en la morfología del cráneo. Los análisis de ADN en 2001 y 2007 también sugirió que eran especies distintas, [23] [11] aunque esta clasificación no fue aceptada universalmente por los expertos. [24] Un estudio de 2010 respaldada sabana africana y los elefantes del bosque son especies distintas. [12] El elefantes pigmeos de la Cuenca del Congo , que han sido sugeridas para ser una especie separada (Loxodonta pumilio) son probablemente los elefantes del bosque cuyo diminutivo tamaño y / o vencimiento anticipado se deben a las condiciones ambientales. [25]

Híbridos

En 1978 en el zoo de Chester , una elefanta asiática dio a luz a un ternero híbrido engendrado por un toro elefante africano arbusto. " Motty ", el resultado ternero macho híbrido, tenía un elefante africano de las mejillas, las orejas (grandes, con lóbulos agudos) y las piernas (más largo y más delgado), pero los números de las uñas (cinco para cada pie delantero, cuatro trasera), y el tronco único dedo de un elefante asiático. Su tronco arrugado era como la de un elefante africano. Su frente estaba inclinada con una cúpula y dos cúpulas más pequeñas detrás de él. El cuerpo era negro en el tipo, pero tenía un tipo asiático centro joroba y una joroba posterior africano-type. El ternero murió de la infección 12 días después. Se conserva en el British Natural History Museum , Londres. [26]

Evolución y parientes extintos

Cráneo de Moeritherium lyonsi en el Museo Nacional de Historia Natural , París , Francia

Más de 161 miembros de la extinta de la orden Proboscidea se han descrito. Tres grandes radiaciones de la proboscidios ocurrido. La radiación comenzó con los primeros miembros, los países de África Eritherium y Phosphatherium de la tarde del Paleoceno . [27] Los Eoceno incluidos anthracobunids del subcontinente indio y Numidotherium , Moeritherium y Barytherium de África. Estos proboscidios primeros fueron relativamente pequeños y acuáticos. Más tarde, géneros como Phiomia y Palaeomastodon surgió, este último bosques habitados probables y bosques abiertos. Proboscidio diversidad disminuyó durante el Oligoceno. [28] Una de las especies notables de esta época fue Eritreum melakeghebrekristosi del Cuerno de África , que pudo haber sido un antepasado de varias especies posteriores. [29] Los proboscidios diversificado al comienzo de la Mioceno , con los deinotheres y los mammutids . El primero se relaciona con Barytherium y vivió en África y Eurasia, [30] mientras que el segundo puede haber descendido de Eritreum [29] y, además, se extendió a América del Norte. [30]

Restauración de Gomphotherium por Charles R. Knight

La segunda radiación estuvo representada por el surgimiento de los gonfoterios en el Mioceno. [30] gonfoterios también pueden haber descendido de Eritreum [29] y se originó en África, se extiende a todos los continentes a excepción de Australia y la Antártida. Los miembros de este grupo incluía Gomphotherium y Platybelodon . [30] La tercera radiación se inició en el Mioceno tardío y dio lugar a la llegada de los elephantids , que descienden de, y reemplazado lentamente, los gonfoterios. [31] Los africanos gomphotheroides Primelephas dio lugar a Loxodonta, Mammuthus y Elephas. Loxodonta ramificado apagado antes, alrededor del Mioceno y Plioceno límite, mientras que Mammuthus y Elephas llegó más tarde durante el Plioceno temprano. Loxodonta permaneció en África, mientras que Mammuthus y Elephas extendió a Eurasia, y la ex llegado a América del Norte. Al mismo tiempo, los stegodontids , otro grupo proboscidio descendientes de gonfoterios, que se distribuyen a lo largo de Asia, incluyendo el subcontinente indio, China, el sureste y el Japón. Además, mammutids seguido evolucionando en nuevas especies, como el mastodonte americano . [32]

Modelo mamut lanudo en el Museo Real de Columbia Británica , Victoria, British Columbia

Al comienzo de la Pleistoceno , elephantids experimentado una alta tasa de especiación . Loxodonta atlantica convirtió en la especie más común en el norte y el sur de África antes de ser reemplazado por iolensis Elephas más tarde en el Pleistoceno. Sólo cuando Elephas se extinguió en África se Loxodonta a ser dominante, una vez más, esta vez en la forma de las dos especies que viven hoy en día. Elephas sería diversificar en nuevas especies en Asia, como E. hysudricus y E. platycephus; [33] . este último es el antepasado probable del elefante asiático moderno [34] Mammuthus evolucionado en varias especies, incluyendo el famoso mamut lanudo . [33] Durante el Pleistoceno tardío , la mayoría de las especies se extinguieron proboscidio. [35]

Proboscidios experimentado varias tendencias evolutivas, tales como un aumento de tamaño, lo que llevó a varias especies gigantes que se alzaban hasta 4 m (13 pies) de altura. Sus miembros se hicieron más largas y las patas más cortas y más amplio. Los primeros proboscidios más desarrollado mandíbulas y cráneos más pequeños, mientras que otros más avanzados desarrollado mandíbulas cortas que cambiaron el centro de gravedad de la cabeza. Además, el cráneo se hizo más grande, especialmente en el cráneo, mientras que el cuello acortado para proporcionar un mejor apoyo para el cráneo. El aumento en el tamaño conducir al desarrollo y la elongación del tronco móvil para proporcionar acceso. El número de premolares, incisivos y caninos disminuido. Las muelas (molares y premolares) se hicieron más grandes y más especializados. Los incisivos superiores segunda creció en colmillos, que variaron en forma de recta, curvada a (ya sea hacia arriba o hacia abajo), a una espiral, dependiendo de la especie. Algunos proboscidios desarrollado colmillos de sus incisiors inferiores. [36]

Especies enanas

Esqueleto de un elefante enano cretense

Varias especies de proboscidios vivido en las islas y con experiencia enanismo insular . Esto ocurrió principalmente durante el Pleistoceno, cuando algunas poblaciones de elefantes quedaron aislados en las islas por las fluctuaciones del nivel del mar, aunque también existían elefantes enanos antes en el Plioceno. Estos elefantes probablemente creció en las islas más pequeñas debido a la ausencia de grandes poblaciones de depredadores o viable y recursos limitados. Por el contrario, los pequeños mamíferos como roedores desarrollar gigantismo en las islas. Proboscidios enanos son conocidos por haber vivido en Indonesia , la Islas del Canal de California , y varias islas del Mediterráneo . [37]

Elephas celebensis de Sulawesi se cree que descienden de planifrons Elephas . Una forma enana de Stegodon también se sabe que han existido en Java . Elephas falconeri de Malta y Sicilia era sólo 1 m (3,3 pies). Era probablemente un descendiente del elefante de colmillos rectos . Otros descendientes del elefante de colmillos rectos existía en Chipre . Mamuts enanos se sabe que han vivido en Cerdeña . Elefantes enanos de origen incierto vivió en Creta , Cícladas y Rodas . [37] El mamut de Columbia se sabe que han colonizado las islas del Canal y se convirtió en el mamut pigmeo . Esta especie alcanza una altura de 1.2 a 1.8 m (3.9 hasta 5.9 pies) y pesan entre 200 kg (440 lb) y toneladas 2. Una población de pequeños mamuts lanudos sobrevivieron en la isla de Wrangel tan recientemente como hace 4.000 años. [37] Después de su descubrimiento en 1993, se consideraron los mamuts enanos. [38] Sin embargo, esta clasificación ha sido re-evaluada y desde la Segunda Internacional del Mamut Conferencia en el año 1999, estos animales ya no se consideran para ser verdad "mamuts enanos". [39]

Anatomía y morfología

Elephant cráneo (corte sagital)

Los elefantes son los animales terrestres más grandes existentes. Hombre elefantes africanos suelen estar 3.20-4.00 m (10.5 a 13.1 pies) de alto y pesan 4,700-6,048 10,000-13,330 kg (lb), mientras que las hembras son típicamente 2.20-2.60 m (7.2 a 8.5 pies) de alto y pesan 2,160-3,232 kg (4,800-7,130 libras). La especie forestal es más pequeño en tamaño que las especies arbustivas. [18] Asia elefantes machos pueden alcanzar 3,20 m (10,5 pies) de altura y pesar hasta 5.400 kg (12.000 libras), mientras que las hembras son 2.24 m (7.3 pies) de alto y pesan 2.720 kg (6.000 libras), en promedio. La cola de un elefante asiático se extiende hasta 1.2-1.5 m (3.9 a 4.9 m) de largo. [15] El esqueleto del elefante se compone de huesos 326-351. [40] Las vértebras están conectadas por uniones estrechas, lo que limita la columna vertebral de flexibilidad. Los elefantes africanos tienen 21 pares de costillas, mientras que los elefantes asiáticos tienen 19-20 parejas. [41]

Esqueleto de elefante africano

El cráneo de un elefante es lo suficientemente resistente como para soportar las fuerzas generadas por la influencia de los colmillos y las colisiones de cabeza a cabeza. La parte posterior del cráneo es aplanado y hacia fuera, creando arcos que protegen el cerebro en cada dirección. [42] El cráneo contiene cavidades de aire ( senos paranasales ) que reducen el peso del cráneo, mientras que mantiene la resistencia global. Estas cavidades dan al interior del cráneo de un panal -como aspecto. El cráneo es especialmente grande y proporciona espacio suficiente para la adherencia de los músculos para soportar toda la cabeza. La mandíbula inferior es sólido y pesado. [40] Debido al tamaño de la cabeza, el cuello es relativamente corto para proporcionar un mejor apoyo. [36] El ojo carece de un aparato lagrimal y se basa en la glándula de Harder para mantenerlo húmedo. El ojo del elefante tiene una duradera membrana nictitante para proteger el planeta. Campo del animal de la visión se ve comprometida por la ubicación y la movilidad limitada de los ojos. [43] Los elefantes son considerados dicrómatas [44] y se puede ver bien con poca luz, pero no en la luz brillante. [45] La temperatura del cuerpo de un elefante promedios de 35,9 ° C (97 ° F), similar a un humano. Al igual que un camello , un elefante puede subir o bajar la temperatura unos pocos grados de la media en respuesta a condiciones ambientales extremas. [46]

Orejas

Vista de un elefante con orejas de propagación, los vasos sanguíneos son visibles en las orejas.

Orejas de elefante tienen bases gruesas con puntas finas. Las orejeras o pinnas , contienen numerosos vasos sanguíneos conocidos como capilares . Para deshacerse del exceso de calor del cuerpo, la sangre caliente fluye en los capilares, que liberan el calor en el ambiente. Esto puede ocurrir naturalmente cuando las pinnas son todavía, pero el animal también puede obligar a este efecto por el aleteo de ellos. Grandes superficies oído contener más capilares, y más calor puede liberarse. Elefantes africanos arbusto vivir en climas más cálidos, y por lo tanto tienen las aletas más grandes para los oídos. [47] Los elefantes son capaces de escuchar a bajas frecuencias, siendo más sensible a 1 k Hz . El oído tiene algunas adaptaciones para la sísmica audiencia; ampliada del oído medio [48] y un único esfínter -como el músculo alrededor del canal auditivo . que constriñe el conducto y permite más fino oído de señales sísmicas [49]

Tronco

Elephant limpiar su ojo con la trompa

El tronco o probóscide , es una fusión de la nariz y el labio superior, a pesar de que a principios fetal vida, el labio superior y el tronco se separan. [36] El tronco es alargado y especializado para convertirse en apéndice más importante y versátil del elefante. Contiene hasta 150.000 distintos fascículos musculares , sin hueso y poca grasa. Estos músculos pares consisten en dos grandes tipos: superficial e interna, el primero se divide en dorsales, ventrales y laterales, mientras que el segundo se divide en los músculos transverso y radiante. Los músculos del tronco conectarse a una abertura ósea en el cráneo. El tabique nasal está compuesto de unidades musculares diminutos que se extienden horizontalmente entre las fosas nasales. Cartílago sólo existe para dividir las ventanas de la nariz en la base. [50] Como hidrostato musculares , el tronco se mueve por contracciones musculares decisivamente coordinados. Los músculos funcionar con y contra otros. Un proboscis único nervio formado por el maxilar y facial nervios -corre a lo largo de ambos lados del tronco. [51]

Elefante con la trompa para beber

Trompas de elefante tienen múltiples funciones, incluyendo la respiración, el olfato , el tacto, sujeción y producción de sonido. [36] sentido del animal del olfato puede ser cuatro veces más sensible que la de un sabueso . [52] La capacidad del maletero es para hacer poderosas torcer y enrollar permite que los movimientos de recogida de alimentos, luchar con sus congéneres , [53] y levantar hasta 350 kg (770 lb). [36] Puede también ser utilizado para tareas delicadas, como limpiar un ojo y comprobar orificios. [53] Se es capaz de romper una cáscara de maní sin romperse la semilla. [36] Con su tronco, un elefante puede llegar a los alimentos a alturas de hasta 7 m (23 pies) y profundamente en el barro o la arena por el agua. [53] Se puede trasvasar agua tanto para pulverizar en la boca para beber y para el cuerpo para la refrigeración. [36] Un elefante asiático adulto es capaz de almacenar 8,5 l (2,2 US gal) de agua en su tronco. [50] Los elefantes también rociar el polvo o la hierba en sí mismos, posiblemente para protegerse de los insectos. [36] Cuando bajo el agua, un elefante puede usar la trompa como un snorkel . [54] La pérdida del tronco sería perjudicial para la supervivencia de un elefante, [36] aunque en casos raros elefantes han sobrevivido con troncos cortos. Además, un elefante se ha observado que pastan al arrodillarse sobre sus patas delanteras, levantando sobre sus patas traseras, y teniendo en hierba con sus labios. [50] Los elefantes pueden mostrar preferencias laterales al agarrar con sus troncos: algunos prefieren torcer a la izquierda, otros a la derecha. [51]

Los elefantes africanos tienen dos prolongaciones en forma de dedos en la punta de la trompa que les permiten agarrar el alimento y llevarlo a la boca. Los elefantes asiáticos tienen una sola y confiar más en envolver alrededor de un alimento y apretándolo en la boca. [6] elefantes asiáticos tienen una mayor coordinación muscular y puede realizar tareas más complejas. [50] El síndrome de tronco Floppy es una condición del tronco parálisis en arbusto africano elefantes. Es causada por la degradación de los nervios periféricos y de los músculos;. comenzando en la punta [55]

Dientes

Primer plano de los dientes, muelas de fallecidos menores arbusto africano elefante

Los elefantes suelen tener 26 dientes: los incisivos , conocidos como los colmillos , 12 hojas caducas premolares y 12 molares . A diferencia de la mayoría de los mamíferos, que crecen los dientes de leche y luego sustituirlos por un único conjunto permanente de los dientes permanentes, los elefantes tienen ciclos de rotación de los dientes a lo largo de toda su vida. Los dientes masticadores se sustituyen en seis ocasiones en la vida de un elefante típico. Los dientes no son sustituidos por otros nuevos que salen de las fauces verticalmente como en la mayoría de los mamíferos. En cambio, los nuevos dientes crecen en la parte posterior de la boca y seguir adelante para expulsar a los antiguos, de forma similar a una cinta transportadora . El primer diente de mascar en cada lado de la mandíbula cae cuando el elefante es de dos a tres años de edad. El segundo conjunto de dientes de mascar cae cuando el elefante es de cuatro a seis años de edad. El tercer juego se pierde en 9-15 años de edad, y juego de cuatro dura hasta 18-28 años de edad. El quinto conjunto de dientes masticadores dura hasta que el elefante está en sus 40 años. El sexto (y por lo general final) juego debe durar el elefante el resto de su vida. Dientes de elefante tiene forma de bucle crestas dentales, que son más gruesas y más en forma de diamante en los elefantes africanos. [56]

Colmillos

Arbusto colmillos de elefantes africanos

Los colmillos de un elefante se modifican los incisivos en la mandíbula superior. Reemplazan los dientes temporales de leche cuando el animal alcanza los 6-12 meses de edad y crecer continuamente en alrededor de 17 cm (6,7 pulgadas) por año. El colmillo está hecho de una forma de fosfato de calcio conocida como marfil . Un colmillo de sección transversal se compone de patrones de líneas entrecruzadas, conocidos como "cambio de motor", que crean en forma de diamante áreas. Como una pieza de tejido vivo, un colmillo es relativamente suave, siendo tan duro como la calcita mineral. Un colmillo de nuevo desarrollo tiene una tapa lisa del esmalte que desaparece con el tiempo. Gran parte de la morsa puede verse externamente, mientras que el resto se fija a un enchufe en el cráneo. La pulpa se extiende a través de una tercera parte del colmillo y posiblemente más tiempo en algunos individuos. Como tal, sería difícil de quitar un colmillo sin dañar al animal. Cuando se retira, marfil comienza a secarse y agrietarse si no se mantiene fresca y húmeda. Los colmillos servir para múltiples propósitos. Se utilizan para excavar en busca de agua, sal y raíces, descortezado o marcar los árboles, y para mover los árboles y las ramas para despejar un camino. También sirven como armas cuando lucha, tanto en ataque como en defensa, y la protección del tronco. [57]

Como los humanos, que suelen ser diestro o zurdo , los elefantes suelen ser de derecha o de izquierda colmillos. El colmillo dominante, llamado el colmillo maestro, es generalmente más desgastado, es más corto y tiene una punta redondeada. A los elefantes africanos, los colmillos están presentes tanto en hombres como en mujeres, y tienen aproximadamente la misma longitud en ambos sexos, alcanzando hasta 3,264 m (10,71 pies), [57] sin embargo, los colmillos de los machos tienden a ser más grueso. [58] En la especie asiática, sólo los machos tienen colmillos grandes. Mujer asiáticos tienen colmillos muy pequeños o están ausentes por completo, una condición que a veces se produce en los hombres. Hombres asiáticos pueden tener colmillos, siempre y cuando los africanos, pero por lo general son mucho más delgado y más ligero, el más grande registrado fue de 3,02 m (9,9 pies) de largo y pesaba 39 kg (86 lb). Los colmillos de los elefantes de la selva de África parecen ser más fuerte y más elástica que la otra especie. [57] La caza de marfil de elefante en África podrían estar llevando a la selección natural más cortos colmillos. [59]

Piel

Detalle de la piel del elefante asiático

La piel de un elefante es generalmente muy difícil, al ser tan gruesa que 2,5 cm (0,98 pulgadas) en la parte posterior y las partes de la cabeza. Sin embargo, la piel alrededor de la boca, el ano y en el interior de la oreja es considerablemente más delgado. Los elefantes jóvenes suelen estar cubiertas de pelo marrón o rojizo, especialmente en la cabeza y espalda. Normalmente, la piel de un elefante asiático está cubierto con más pelo que sus contrapartes africanas. [60] De las dos especies africanas, el elefante de bosque tiende a ser más peludo. [6] Como los elefantes crecen, su pelo se oscurece y se vuelve más escaso , pero siempre permanecerá en sus cabezas y colas. [60] pelo escasamente espaciados podría permitir que el animal se pierde más calor. [61]

Los elefantes son generalmente de color grisáceo, pero los elefantes africanos muy a menudo aparecen de color marrón o rojizo de revolcarse en el barro en un hoyo de tierra de color. Además, elefantes asiáticos tienen algunas manchas de despigmentación, particularmente en la frente y alrededor de las orejas. Un elefante con barro como un filtro solar, protegiendo su piel de duras ultravioleta luz. Aunque difícil, la piel de un elefante es muy sensible. Sin baños de barro regulares a lo protegen de la combustión, así como de las picaduras de insectos y la pérdida de humedad, la piel de un elefante sufre daños graves. Después del baño, el elefante suele usar la trompa para volar del suelo en su cuerpo para ayudar a secar y cocer en su escudo protector nuevo. [60]

Wallowing también ayuda a la piel en la regulación de la temperatura corporal. Los elefantes tienen dificultad con liberación de calor a través de la piel debido a su alta área superficial a volumen . La relación de la masa de un elefante a la superficie de su piel es muchas veces mayor que la de un humano. Los elefantes han sido observados incluso levantar sus piernas para exponer las plantas de los pies, presumiblemente en un esfuerzo para exponer más piel al aire. [60]

Piernas, locomoción y la postura

Elefante caminando

Para apoyar el peso del animal, las extremidades de un elefante se colocan verticalmente más bajo del cuerpo que en la mayoría de los otros mamíferos. Los huesos largos de las extremidades tienen hueso esponjoso en lugar de cavidades medulares . Esto refuerza los huesos mientras que todavía permite la producción de células sanguíneas. [62] Tanto la parte delantera y miembros posteriores pueden soportar el peso de un elefante, aunque el 60% es soportado por la parte delantera. [63] Puesto que los huesos de las extremidades se colocan una encima de la otra y bajo el cuerpo, un elefante puede estar quieto durante largos períodos de tiempo sin utilizar mucha energía. [62] Las patas circulares de un elefante tienen tejidos blandos o "pads" cojín debajo de la manus o pes . Estas pastillas ayudan a distribuir el peso del animal. [63] elefantes son incapaces de girar sus extremidades anteriores, como el cúbito y radio están fijos en pronación ;. la "palma" de la manus enfrenta hacia atrás [62] Además, la pronador cuadrado y el pronador redondo se han reducido o ausente. [64] hasta cinco uñas de los pies se puede encontrar en la parte delantera y patas traseras. [6] En 2011, científicos de la Universidad Real de Veterinaria descubrió que los elefantes tienen un hueso sesamoideo , un extra de "dedo del pie" similar en la colocación de un panda gigante 's extra "pulgar". This extra toe acts to support and distribute the weight of the elephant. [ 65 ]

Elephant swimming and snorkeling

Elephants can move both forwards and backwards, but cannot trot , jump , or gallop . They use only two gaits when moving on land, the walk and a faster gait similar to running. [ 62 ] In walking, the legs act as pendulums, with the hips and shoulders rising and falling while the foot is planted on the ground. With no "aerial phase", the fast gait does not meet all the criteria of running, however, the elephant uses its legs much like other running animals, with the hips and shoulders falling and then rising while the feet are on the ground. [ 66 ] Fast-moving elephants appear to 'run' with their front legs, but 'walk' with their hind legs and can reach a top speed of 18 km/h (11 mph). [ 67 ] At this speed, most other quadrupeds are well into a gallop, even accounting for leg length. Spring-like kinetics could explain the difference between the motion of elephants and other animals. [ 68 ]

When moving, the cushion pads expand and contract, and reduce both the pain and noise that would come from a very heavy animal moving. [ 63 ] Elephants are capable swimmers. They have been recorded swimming for up to six hours without touching the bottom, and have traveled as far as 48 km (30 mi) a stretch and at speeds of up to 2.1 km/h (1.3 mph). [ 69 ] While they may doze off while standing, elephants usually sleep laying down. [ 62 ]

Internal and sexual organs

African bush elephant heart in a jar
Penis of an Asian elephant
Vulva of an Asian elephant

The brain of an elephant weighs 4.5–5.5 kg (9.9–12 lb) compared to 1.6 kilograms (3.5 lb) for a human brain. However, while the elephant brain is larger overall, it is proportionally smaller. At birth, an elephant's brain already weighs 30–40% of an adult's. The brain's cerebrum and cerebellum are well developed, and the temporal lobes are so large that they bulge out laterally. [ 46 ] The throat of an elephant appears to contain a pharyngeal pouch in which it can store water for later use. [ 36 ]

The heart of an elephant weighs 12–21 kg (26–46 lb). It has a double-pointed apex , an unusual trait among mammals. [ 46 ] When standing, the elephant's heart beats approximately 30 times per minute. In contrast to many other animals, the heart rate is faster when lying down, beating at a rate of 8 to 10 beats per minute faster. [ 70 ] The lungs are attached to the diaphragm , [ 46 ] and connective tissue exists in place of the pleural cavity . [ 54 ] As such, breathing relies mainly on the diaphragm rather than expansion of the ribcage. [ 46 ] This may allow the animal to deal with the pressure differences when its body is underwater and its trunk is breaking the surface for air, [ 54 ] although this explanation has been questioned. [ 71 ] Another possible function for this adaptation is that it helps the animal suck up water through the trunk. [ 54 ] An elephant inhales most of its air though the trunk, although some goes through the mouth. Elephants have a hindgut fermentation system, and their large and small intestines together reach 35 m (115 ft) in length. The majority of an elephant's intake goes undigested despite the process lasting up to a day. [ 46 ]

A male elephant's testes are located internally near the kidneys. The penis can reach a length of 100 cm (39 in) and a diameter of 16 cm (6.3 in) at the base. It is S-shaped when fully erect and has a Y-shaped orifice . The female has a well-developed clitoris at up to 40 cm (16 in). The vulva is located between the hind legs instead of near the tail as in most mammals. Determining pregnancy status can be difficult due to the animal's large abdominal cavity . The female's mammary glands occupy the space between the front legs, which puts the suckling calf within reach of the female's trunk. [ 46 ] Elephants have a unique organ, the temporal gland, located in both sides of the head. This organ is associated with sexual behavior, and males secrete a fluid from it when in musth . [ 72 ] Females have also been observed with secretions from the temporal glands. [ 52 ]

Behavior and life history

Ecology and activities

Elephant foraging

The African bush elephant can be found in habitats as diverse as dry savannas , deserts , marshes , and lake shores and in elevations from sea level to mountain areas above the snowline. Forest elephants mainly live in equatorial forests , but will also enter gallery forests and ecotones between forests and savannas. [ 22 ] Asian elephants prefer areas with a mix of grasses, low woody plants and trees, primarily inhabiting dry thorn-scrub forests in southern India and Sri Lanka and evergreen forests in Malaya . [ 15 ] Elephants are herbivorous and will eat leaves, twigs, fruit, bark and roots. The African species are mostly browsers; the Asian elephants are mainly grazers. They can consume as much as 150 kg (330 lb) of food and 40 L (11 USgal) of water in a day. Elephants tend to stay near water sources. [ 22 ] Major feeding bouts take place in the morning, afternoon and night. At midday, elephants rest under trees and may doze off while standing. Sleeping occurs at night while the animal is lying down. [ 73 ] Both males and family groups have restricted daily movements, moving 10–20 km (6.2–12 mi), but distances as far as 90–180 km (56–110 mi) have been recorded in the Etosha region of Namibia . [ 74 ] They are known to go on seasonal migrations in search of food, water and mates. At Chobe National Park , Botswana , elephant herds travel 325 km (202 mi) to visit the river when the local waterholes dry up. [ 75 ]

Elephants bathing

Because of their large size, elephants have a huge impact on their environments and are considered keystone species . Their habit of uprooting trees and undergrowth can transform savannas into grasslands; when they dig for water during drought, they create waterholes that can be used by other animals. They can also enlarge waterholes when they bathe and wallow in them. At Mount Elgon , Kenya , elephants "excavate" caves that are used by ungulates, hyraxes, bats, birds and insects. [ 76 ] Elephants are important seed dispersers ; in particular, ingestation and defecation of seeds by African forest elephant tends to have either no effect or a positive effect on their germination and they are typically dispersed in large amounts over great distances. [ 77 ] A 2012 study on Asian forests found that large seeds require giant herbivores like elephants and rhinoceros for transport and dispersal; an ecological niche that can not be filled by the next largest herbivore, the tapir . [ 78 ] Because most of the food they eat goes undigested, their dung can provide food for other animals, such as dung beetles and monkeys. [ 76 ] Elephants can also have a negative impact on ecosystems. At Murchison Falls National Park in Uganda , the overabundance of elephants has threatened several species of small birds that depend on woodlands. In addition, their weight can compact the soil, which causes the rain to run off , leading to erosion . [ 73 ]

The size of adult elephants makes them nearly invulnerable to predators. However, calves may be preyed on by lions , spotted hyenas , and wild dogs in Africa [ 18 ] and tigers in Asia. [ 15 ] The lions of Savuti , Botswana, have adapted to hunting elephants during the dry season, and a pride of 30 lions has been recorded to kill elephants between the ages of four and 12 years. [ 79 ] Elephants typically coexist peacefully with other herbivores, which will usually stay out their way. Some aggressive interactions between elephants and rhinoceros have been recorded. At Aberdare National Park , Kenya, a rhino attacked an elephant calf and was subsequently killed by the other elephants in the group. [ 73 ] At Hluhluwe–Umfolozi Game Reserve , South Africa , introduced young orphan elephants went on a killing spree that claimed the lives of 36 rhinos during the 1990s, but ended with the introduction of older males. [ 80 ] Elephants tend to have a high load of parasites, particularly nematodes . This may be due to their low predation pressures in comparison with other herbivores. [ 81 ]

Social organization

Elephant family in Amboseli National Park

The social lives of male and female elephants are very different. The females spend their entire lives in tight-knit family groups, some of which are made up of mothers, daughters, sisters, and aunts. These family groups can have more than 10 members, including three pairs of mothers with offspring, and are led by the eldest female, or matriarch . [ 82 ] The matriarch remains leader of the group until she no longer has the energy for the role; [ 83 ] a study on zoo elephants showed that when the matriarch died, the levels of faecal corticosterone ('stress hormone') dramatically increased in the surviving elephants. [ 84 ] The social circle of the female elephant does not necessarily end with the small family unit. At Amboseli National Park , Kenya, a female's life also involves interaction with other families, clans, and subpopulations. Family groups may associate and bond with certain other family groups, forming what are known as bond groups. These are typically made of two family groups. During the dry season, elephant families may cluster together and form another level of social organization known as the clan. Groups within these clans do not form strong bonds, but they defend their dry-season ranges against other clans. There are typically nine groups in a clan. The Amboseli elephant population is further divided into the "central" and "peripheral" subpopulations. [ 82 ]

Lone bull elephant

Some elephant populations in India and Sri Lanka have similar basic social organizations. There appear to be cohesive family units and loose aggregations. They have also been observed to have "nursing units" and "juvenile-care units". In southern India, elephant populations may contain family groups, bond groups and possibly clans. Family groups tend to be small, consisting of one or two adult females and their offspring. A group containing more than two adult females plus offspring is known as a "joint family". Malay elephant populations have even smaller family groups, and do not have any social organization higher than a family or bond group. Groups of African forest elephants typically consist of one adult female with one to three offspring. These groups appear to interact with other groups, especially at forest clearings. [ 82 ]

The life of the adult male is very different. As he ages, a male begins to spend more time at the edge of his group and associates with outside males or even strange families. At Amboseli, young males spend over 80 percent of their time away from their natal group when they are 14–15. The adult females of the group start to show aggression towards the male, which encourages them to permanently leave the group. When males do leave, they either live alone or with other males. The former is typical of males in dense forests. Asian males are usually solitary, but do occasionally form groups of two or more individuals. The largest of such groups consisted of seven bulls. Larger bull groups consisting of over 10 members occur only among African bush elephants, the largest of which numbered up to 144 individuals. A dominance hierarchy exists among males, whether they range socially or solitarily. Dominance depends on the age, size and sexual condition. [ 85 ] Old bulls appear to control the aggression of younger ones and prevent them from forming "gangs". [ 86 ] Adult males and females come together for reproduction. Bulls appear to associate with family groups if an estrous cow is present. [ 85 ]

Musth and mating

Elephant in musth

Adult bulls enter a state of increased testosterone known as musth . The main characteristic of a bull's musth is a fluid secreted from the temporal gland that runs down the side of its face. It may also urinate with the penis still in the sheath , which causes the urine to spray on the hind legs. Behaviors associated with musth include walking with the head held high and swinging, picking at the ground with the tusks, marking, rumbling and waving only one ear at a time. This can last from a day to four months. Younger bulls appear to enter musth during the dry season (January–May), while older bulls go through it during the wet season (June–December). [ 87 ] In a population in southern India, males first enter musth at the age of 15, but it is not very intense until they are older than 25. At Amboseli, bulls under 24 do not go into musth, while half of those aged 25–35 and all those over 35 do. [ 87 ]

Male elephants become extremely aggressive during musth. Among both musth and nonmusth bulls, size is the determining factor in agonistic encounters. However, in contests between individuals from the two groups, musth bulls win the majority of the time, even when the nonmusth bull is larger. A bull may stop showing signs of musth when it encounters a musth bull of higher rank. Musth bulls of equal rank tend to avoid each other. Agonistic encounters typically consist of threat displays, chases and minor sparring with the tusks. Serious fights are rare. [ 87 ]

Bull mating with a member of a female group

Elephants are polygynous breeders, [ 88 ] and copulations are most frequent during peak rains. [ 89 ] Females are sexually mature by the age of nine years and can come into estrous, mate and give birth. [ 90 ] Males become mature around 14–15 years. [ 85 ] The estrous cycle of a cow lasts 14–16 weeks with a four- to six-week follicular phase and an eight- to 10-week luteal phase . While most mammals have one surge of luteinizing hormone during the follicular phase, elephants have two. The first surge, known as the anovulatory surge, could signal to males that the female is in estrus by changing her odor, but ovulation does not occur until the second, ovulatory surge. [ 91 ]

A cow in estrus will release chemical signals ( pheromones ) in her urine and vaginal secretions to advertise her sexual condition. A bull will follow a potential mate and assess her condition with the flehmen response , as in many mammal species. In the case of elephants, it requires the male to collect a chemical sample with his trunk and bring it to the vomeronasal organ . [ 92 ] Bulls achieve reproductive success through mate-guarding, which involves a male tending to an estrous female and defending her from other males. The majority of mate-guarding is done by musth males, and females actively seek to be guarded by them, particularly older ones. [ 93 ] Musth appears to signal to females the condition of the male, as weak or injured males do not have normal musths. [ 94 ] Musth bulls thus have more reproductive success. [ 85 ] For young females, the approach of an older bull can be intimidating, so her relatives stay nearby for support and reassurance. [ 90 ] During copulation, the male lays his trunk over the female's back. [ 95 ] Fertility rates in cows decline around 45–50 years of age. [ 83 ] Same-sex relations are common and frequent in both sexes, with Asian elephants in captivity devoting roughly 46% of sexual encounters to same-sex activity. [ 96 ]

Lifecycle

Mother elephant with calf

Gestation in elephant typically lasts 18–23 months with interbirth intervals usually lasting four to five months. Births tend to take place during the rains. [ 97 ] Calves are born 85 cm (33 in) tall and weigh around 120 kg (260 lb). [ 90 ] Newborn elephants are precocial and quickly stand and walk to follow their mother and family herd. [ 98 ] A new calf is usually the center of attention for herd members. Adults and most of the other young will gather around the newborn, touching and caressing it with their trunks. For the first few days, the mother is intolerant of the other herd members being near her young. Alloparenting —where a calf is cared for by someone other than its mother—is known to exist in some family groups. A mother may have a younger female helper known as an allomother. These allomothers are typically two to 12 years old and will help watch over the young calf. [ 90 ] When a predator is near, the family group bunches together with the calves in the center. [ 99 ]

For the first few days, the newborn stumbles and falls, and needs the support of its mother. It relies on touch, smell and hearing, as its eyesight is poor. It also has little precise control over its trunk, which wiggles around and may cause it to trip. By its second week of life, the calf can walk more firmly and has more control over its trunk. After its first month, a calf can pick up, hold and put objects in its mouth, but cannot suck water through the trunk and must drink directly through the mouth. It is still dependent on its mother and keeps close to her. [ 98 ]

For its first three months, a calf relies entirely on milk from its mother for nutrition. Afterwards, it begins to forage for vegetation and can use its trunk to collect water. Improvements in lip and leg coordination also occur. Calves continue to suckle at the same rate as before until their sixth month, after which they become more independent when feeding. By nine months, mouth, trunk and foot coordination is perfected. After a year, a calf's abilities to groom, drink, and feed itself are fully developed. However, they still need their mothers for nutrition and protection from predators for at least another year. Suckling bouts tend to last 2–4 min/hr for a calf younger than a year. It continues to suckle until it reaches three years of age or older. Suckling after two years may serve to maintain growth rates, body condition and reproductive ability. [ 98 ] Play behavior in calves differs between the sexes. Females run or chase each other, while males play-fight. While females remain in their family groups for life, males leave to lead a solitary life or join all-male groups. [ 90 ] Elephants have long lifespans, reaching 60–70 years of age. [ 56 ]

Comunicación

Elephants touching each other's mouths which is a form of greeting.

Touching is an important form of communication among elephants. Individuals greet one another by stroking or wrapping around each other's trunks. Entwining trunks are also made during mild competition. Older elephants use trunk-slaps, kicks or shoving to discipline younger ones. Individuals of any age and sex will touch each other's mouths, temporal glands and genitals, particularly during meetings or when excited. Touching is especially important for mother–calf communication. When moving, elephant mothers will touch their calves with their trunks or feet when side-by-side or with their tails if the calf is behind them. When it wants to suckle, a calf will touch its mother's breast or leg. When the herd is on the move and a calf wants to rest, it will press against its mother's front legs. [ 100 ]

Elephants also communicate with visual displays, mostly in agonistic situations. They will try to appear more threatening by raising their heads and spreading their ears. They may also add to the display by shaking their heads and snapping their ears, as well as throwing dust and vegetation. Elephants are usually bluffing when performing these actions. Excited elephants may additionally raise their trunks. Submissive elephants will lower their heads and trunks, as well as flatten their ears against their necks, while those that accept a challenge will position their ears in a V shape. [ 101 ]

Elephants produce a number of sounds, usually through the larynx , though some may be modified by the trunk. Perhaps the most well-known is the trumpet, which is made during excitement, distress or aggression. [ 102 ] Fighting elephants may roar or squeal, and wounded ones may bellow. [ 103 ] Rumbles are produced during mild arousal. [ 104 ] Some rumbles appear to be infrasonic . [ 105 ] Infrasonic calls are important, particularly for long-distance communication, [ 102 ] in both Asian and African elephants. For Asian elephants, these calls have a frequency of 14–24 Hz , with sound pressure levels of 85–90 dB and last 10–15 seconds. [ 105 ] For African elephants, calls range from 15–35 Hz and can be as loud as 117 dB, allowing communication for many kilometers, with a possible maximum range of around 10 km (6 mi). [ 106 ]

Elephant family responding to playback of rumbles from another family

At Amboseli, several different infrasonic call have been identified. A greeting rumble is emitted by members of a family group after having been separated for several hours. Contact calls are soft, unmodulated sounds made by individuals which have been separated from their group, which may be responded to with a "contact answer" call, which starts out loud, but becomes softer. A "let's go" soft rumble is emitted by a female to signal to the other herd members that it is time to move to another spot. Bulls in musth emit a distinctive, low-pulsated rumble nicknamed the "motorcycle". Musth rumbles may be answered by the "female chorus", a low-frequency, modulated chorus produced by several cows. The postcopulatory call, a loud call, is produced by an estrous cow, mostly after mating. When a cow has mated, her family may produce calls of excitement known as the "mating pandemonium". [ 104 ]

Elephants may also use seismic communication from signals produced by impacts on the earth's surface or acoustical waves that travel through it. Elephants appear to rely on their leg and shoulder bones to transmit the signals to the middle ear. When detecting seismic signals, the animals lean forward and put more weight on their larger front feet; this is known as the "freezing behavior". Elephants posses several adaptations suited for seismic communication. The cushion pads of the feet contain cartilaginous nodes and have similarities to the acoustic fat found in marine mammals like toothed whales and sirenians . In addition, the muscle surrounding the ear canal can constrict the passageway, thereby dampening acoustic signals and allowing the animal to hear more seismic signals. [ 49 ] Elephants appear to use seismics for a number of purposes. An elephant running or mock charging can create seismic signals that can be heard at great distances. [ 107 ] Seismic waveforms produced by locomotion appear to travel at distances of up to 32 km (20 mi) while those from vocalizations travel 16 km (9.9 mi). When detecting the seismics of an alarm call signaling danger from predators, elephants enter a defensive posture and family groups will pack together. [ 108 ]

Intelligence and cognition

Human, pilot whale and elephant brains to scale: (1)- cerebrum (1a)- temporal lobe and (2)- cerebellum

Elephants are among the most intelligent species; their psychology is comparable to primates . [ 45 ] They exhibit mirror self-recognition , an indication of self-awareness and cognition that has also been demonstrated in some apes and dolphins . [ 109 ] One study of a captive female Asian elephant suggested the animals are capable of learning and distinguishing between several visual and some acoustic discrimination pairs. The subject was even able to score a high accuracy rating when retested with the same visual pairs a year later. Elephants are also among the few species known to use tools. An Asian elephant was recorded modifying branches and using them as flyswatters. However, tool modification by elephants is not as advanced as that done by chimpanzees . Elephants are popularly thought of as having an excellent memory. This could have a factual basis; elephants possibly have cognitive maps to allow them to remember large-scale spaces over long periods of time. In addition, individuals appear to be able to keep track of the current location of their family members. [ 45 ] Scientists debate the extent to which elephants feel emotion . They appear to have some ritual around death and show a keen interest in the bones of their own kind, regardless of whether they are related. A dying or dead elephant seems to elicit attention and it has been claimed evokes compassion in others, including those from other groups. [ 110 ]

Conservation issues

Status

Current distribution of elephants

African elephant (both species)
Asian elephant

African elephants were listed as Vulnerable by the IUCN in 2008, with no independent assessment of the conservation status of the two forms. [ 111 ] In 1979, Africa had an estimated minimum population of 1.3 million elephants, with a possible upper limit of 3.0 million. Ten years later in 1989, the population was estimated to be 609,000; with 277,000 in Central Africa , 110,000 in eastern Africa , 204,000 in southern Africa , and 19,000 in western Africa . About 214,000 elephants were estimated to live in the rainforests, less than had previously been thought. From 1977 to 1989, elephant populations declined by 74% in East Africa. Since 1987, losses in elephant numbers accelerated, with savanna populations from Cameroon to Somalia experiencing a decline of 80%. African forest elephants had a total loss of 43%. Population trends in southern Africa were mixed, with anecdotal reports of losses in Zambia , Mozambique and Angola , while populations grew in Botswana and Zimbabwe and were stable in South Africa. [ 112 ] However, studies in 2005 and 2007 found populations in eastern and southern Africa were increasing by an average annual rate of 4.0% per year. [ 111 ]

African elephants receive at least some legal protection in every country where they are found, but 70% of their ranges exist outside of protected areas. In 1989, the African elephant was listed under Appendix I by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), making trade of them illegal. However, annotations were given to Botswana, Namibia and Zimbabwe in 1997 and South Africa in 2000. These countries now have African elephants listed under Appendix II (allowing restricted trade). In some range countries, sport hunting of elephants is legal, with Botswana, Cameroon, Gabon , Mozambique, Namibia, South Africa, Tanzania , Zambia , and Zimbabwe having CITES export quotas for elephant trophies. Successful conservation efforts in certain areas have led to large elephant population densities. As of 2008, numbers and local densities are controlled by contraception or translocation. Large-scale cullings ceased in 1988, when Zimbabwe abandoned the practice. [ 111 ] In 2008, the IUCN listed the Asian elephant as Endangered due to a 50% population decline over the past 60–75 years. [ 113 ] This species was known to have ranged from Syria and Iraq to China (up to the Yellow River ) [ 114 ] and Java . It is now extinct in these areas, [ 113 ] and their current range is heavily fragmented. [ 114 ] The total population of Asian elephants is estimated to be approximately 40,000–50,000, although this may be a "crude guess". [ 113 ] Nearly half of the population likely exists in India . Although Asian elephants are declining in numbers overall, particularly in Southeast Asia , the population in the Western Ghats appears to be increasing. CITES lists the species under Appendix I. [ 113 ]

Threats

Men with elephant tusks at Dar es Salaam , Tanzania, circa 1900

The poaching of elephants for their ivory has been one of the major threats to their existence. Historically, numerous cultures made ornaments and other works of art from elephant ivory, and its use rivaled that of gold. [ 115 ] Hunting for ivory was blamed for the African elephant population decline. [ 111 ] This prompted international bans on ivory imports, starting with the United States in June 1989, and followed by bans in other North American countries, western European countries, and Japan. [ 115 ] Around the same time, Kenya had its ivory stocks burned. [ 116 ] CITES approved an international ban on ivory which went into effect in January 1990. [ 115 ]

Following the bans, unemployment rose in India and China, where the ivory industry was important economically. By contrast, Japan and Hong Kong, which were also part of the industry, were able to adapt and were not badly affected economically. [ 115 ] Zimbabwe, Botswana, Namibia, Zambia, and Malawi wanted to continue the ivory trade and were allowed to, since their populations were healthy, but only if their supplies were from elephants that had been culled or died of natural causes. [ 116 ] The ban allowed the African elephant to recover in parts of Africa. [ 115 ] In January 2012, hundreds of elephants in Bouba Njida National Park , Cameroon, were killed by Chadian raiders. This has been called "one of the worst concentrated killings" since the ivory ban. The ivory of the forest elephant is considered more valuable than that of the bush elephant. [ 116 ] Asian elephants are potentially less vulnerable to the ivory trade, as females usually lack tusks. However, members of the species have been killed for their ivory in some areas, such as Periyar National Park , India. In addition, they are poached for their meat and hides. Poaching for all three items has been linked to population declines in Southeast Asia. [ 113 ]

Other threats to elephants include habitat destruction and fragmentation, which further lead to direct conflicts with humans. [ 111 ] The Asian elephant lives in areas with some of the highest human populations. Because they need larger amounts of land than other sympatric terrestrial mammals, they are the first to be affected by human encroachment. In extreme cases, elephants may be confined to small islands of forest among human-dominated landscapes. In addition, elephants cannot coexist with humans in agricultural areas due to their size and food requirements. Elephants commonly trample and consume crops, which contributes to conflicts with humans, and both elephants and humans have died by the hundreds as a result. Mitigating these conflicts is important for conservation. [ 113 ]

Elephants and humans

Beast of burden

Working elephant being used for transportation

Elephants have been working animals at least since the Indus Valley Civilization [ 117 ] and continue to be used in modern times, with 13,000–16,500 working elephants employed in Asia. These animals are typically captured from the wild when they are 10–20 years old, which is when they can be trained quickly and easily, and have a longer working life. [ 118 ] They were traditionally captured with traps and lassos , but since 1950, tranquilizers are used instead, being potentially less harsh. [ 119 ] People who work with elephants are known as mahouts . Elephants perform various tasks, including hauling loads into remote areas, moving logs out of forests and into trucks, transporting tourists around national parks, pulling goods on wagons and leading religious processions. [ 118 ]

Elephants are valued as working animals over mechanized tools because they can work in relatively deep water, require relatively little maintenance, need only vegetation and water as fuel and can be trained to memorize specific tasks. They can be trained to respond to over 30 commands. [ 118 ] However, musth bulls can be difficult and dangerous to work with, so they are chained until the condition passes. [ 120 ] While the training of elephants into working animals is usually done with Asian elephants, this practice has been done in Africa as well. Leopold II of Belgium is known to have captured and trained elephants in the Belgian Congo during the 19th century. Since then, elephants have been used in agriculture, forestry and tourism. [ 121 ] In India, many working elephants are alleged to have been subject to abuse. They and other captive elephants are thus protected under the The Prevention of Cruelty to Animals Act of 1960 . [ 122 ]

Warfare

Elephants were considered formidable instruments of war and were the "armored tanks" of antiquity. War elephants were equipped with armor to protect their sides, and their tusks were given sharp points of iron or brass if they were large enough. These animals were trained to grasp an enemy soldier and toss him to their rider or to pin the soldier to the ground and impale him. They could also use their trunks for tripping. [ 123 ]

One of the early references to war elephants is in the Mahabharata (written in the 4th century BCE but is said to describe events between the 11th and 8th centuries BCE). The animals were important in four-arm fighting forces or chaturngini sene . However, they were not used as much as horse-drawn chariots by either the Pandavas or Kauravas . Experts on elephant warfare were said to be from indigenous tribes. During the Magadha Kingdom (which began in the 6th century BCE), elephants began to achieve greater cultural importance than horses, and later Indian kingdoms used war elephants extensively; 3,000 of them were sent to be used in the Nandas (5th and 4th centuries BCE) army, while 9,000 may have been used in the Mauryan army (between the 4th and 2nd centuries BCE). The Arthashastra (written around 300 BCE) advised the king to reserve some forests for wild elephants for use in the army, and that anyone who killed an elephant must be executed. [ 124 ]

The Achaemenid Empire (between the 6th and 4nd centuries BCE) also used war elephants. Alexander the Great was able to train his foot soldiers to injure the animals and cause them to panic during wars with both the Persians and Indians. Ptolemy , who was one of Alexander's generals, used corps of Asian elephants during his reign as the ruler of Egypt (which began in 323 BCE). His son and successor Ptolemy II (who began his rule in 285 BCE) obtained his supply of elephants further south at Nubia . Since then, war elephants were employed throughout the Mediterranean and North Africa. Greek king Pyrrhus used elephants in his attempted invasion of Rome in 280 BCE. While they did frighten the Roman horses, they were not decisive and Pyrrhus ultimately lost the battle. The Carthaginian general Hannibal took elephants across the Alps during his war with the Romans and managed to reach the Po Valley in 217 BCE with all of them alive, but they later succumbed to disease. [ 123 ]

Zoos and circuses

Elephants being observed at the Barcelona Zoo

Around 1,200 Asian and 700 African elephants are kept in zoos and circuses . The largest captive population is in North America, which has an estimated 370 Asian and 350 African elephants. About 380 Asians and 190 Africans are known to exist in Europe, and Japan has around 70 Asians and 67 Africans. [ 125 ] Most African elephants in zoological gardens are the bush elephants. Some in Europe, Japan and Africa, though, house forest elephants. [ 126 ] Elephants have traditionally been a major part of circuses around the world, being intelligent enough to be trained in a variety of acts. [ 125 ]

Elephants were historically kept for display in the menageries of Ancient Egypt , China, Greece and Rome . The Romans in particular pitted elephants against humans and other animals in bloody arena battles. In the modern era , the United States received its first elephant, an Asian female, on 13 April 1796. In 1824, the first African elephant, also a female, arrived in the US. The first born in the US was a female Asian elephant on 10 March 1880 at Cooper and Bailey Circus in Philadelphia; a stillborn Asian was delivered at the London Zoo on 31 August 1902. The first known birth of an African elephant in Europe occurred at a Munich zoo on 11 April 1943, and the United States had its first African elephant born at the Knoxville Zoo on 2 March 1978. Elephants do not reproduce well in captivity, due to the difficulty of handling musth bulls and a lack of understanding of female estrous cycles. [ 125 ] Asian elephants were always more common than their African counterparts in modern zoos and circuses. When CITES listed the Asian elephant under Appendix I in 1975, the number of African elephants in zoos increased in the 1980s, although the import of Asians continued. Subsequently, the US received many of its captive African elephants from Zimbabwe, which had an overabundance of the animals. [ 125 ]

Circus poster featuring elephants

Keeping elephants in zoos has been met with some controversy. Proponents of zoos argue that they offer researchers easy access to the animals and provide money and expertise for preserving their natural habitats, as well as safekeeping for the species. Critics claim that the animals in zoos are under physical and mental stress. Elephants and other animals have been recorded displaying stereotypical behaviors . [ 127 ] In the case of elephants, this comes in the form of swaying back and forth, trunk swaying or route tracing. Up to 54% of elephants in UK zoos display stereotypical behaviors. [ 128 ] Elephants in European zoos appear to have shorter lifespans than their wild counterparts at only 17 years, although other studies suggest that zoo elephants live as long those in the wild. Supporters of zoos insist that the care of animals has improved and activities are used to help reduce stress. [ 129 ]

The use of elephants in circuses has also been controversial. The Humane Society of the United States has accused circuses of mistreating their animals and causing them stress. [ 130 ] In testimony to a US federal court in 2009, Ringling Bros. and Barnum & Bailey Circus CEO Kenneth Feld acknowledged that circus elephants are struck behind their ears, under their chins and on their legs with metal-tipped prods, called bull hooks or ankus. Feld stated that these practices are necessary to protect circus workers. He also acknowledged that an elephant trainer was reprimanded for using an electric shock device, known as a hot shot or electric prod, on an elephant. However, Feld denied that any of these practices harm elephants. [ 131 ] Some trainers have tried to train elephants without the use of physical punishment. Ralph Helfer is known to have relied on gentleness and reward when training his animals, including elephants and lions. [ 132 ]

Elephant mock charging tourists in Corbett National Park

Ataques

Elephants can experience bouts of rage and engage in actions against humans which have been interpreted as vindictive. [ 133 ] In Africa, groups of adolescent elephants attacked human villages after cullings were done in the 1970s and '80s. [ 134 ] [ 86 ] In India, male elephants regularly attack villages at night, destroying homes and killing people. Elephants killed around 300 people between 2000 and 2004 in Jharkhand , while in Assam 239 people were reportedly killed between 2001 and 2006. [ 133 ] Local people have reported their belief that some elephants were drunk during their attacks, although officials have disputed this explanation. [ 135 ] [ 136 ] Purportedly drunk elephants raided Indian village again in December 2002, killing six people, which led to the killing of about 200 elephants by locals. [ 137 ]

Cultural depictions

Granite carving of elephant, Mahabalipuram , India.

Elephants have been represented in art since Paleolithic times. Africa in particular contains many rock paintings and engravings of the animals, especially in the Sahara and southern Africa. Those of the latter were created by the Bushmen . [ 138 ] In the Far East , the animals are depicted as motifs in Hindu and Buddhist shrines and temples. [ 139 ] Elephants are often difficult to portray by people with no first-hand experience with them. [ 140 ] The ancient Romans, who kept the animals in captivity, depicted anatomically accurate elephants on mosaics in Tunisia and Sicily. At the beginning of Middle Ages , though, when Europeans had little to no access to the animals, elephants were portrayed more like fantasy creatures. They were often depicted with horse- or bovine-like bodies with trumpet-like trunks and tusks like a boar; some were even given hooves. Elephants were commonly featured in motifs by the stonemasons of the Gothic churches. As more elephants began to be sent to European kings as gifts during the 15th century, depictions of them became more accurate, including one made by Leonardo da Vinci . However, some Europeans continued to portray them in a more stylized fashion. [ 141 ] Max Ernst 's famous 1921 surrealist painting The Elephant Celebes depicts an elephant as a silo with trunk-like hose protruding from it. [ 142 ]

Woodcut illustration for " The Elephant's Child " by Rudyard Kipling .

Elephants have been the subject of religious beliefs. The Mbuti people believe the souls of their dead ancestors resided in elephants. [ 139 ] Similar beliefs existed among certain other African tribes, who believed their chiefs would be reincarnated as elephants. During the 10th century AD, the people of Igbo-Ukwu buried their leaders with elephant tusks. [ 143 ] The animals' religious importance was only at the totemic level in Africa. [ 144 ] Elephants had a much greater role in the religions of Asia. In Sumatra, elephants have been associated with lightning. Likewise in Hinduism, they are linked with thunderstorms as Airavata , the father of all elephants, represents both lightning and rainbows. [ 139 ] One of the most important Hindu deities, the elephant-headed Ganesha , is considered to be on par with the supreme gods of the Hindu triumvirate. [ 145 ] Ganesha is associated with writers and merchants, and could give people success and grant them their desires. [ 139 ] In Buddhism, the Buddha himself is believed to have been a white elephant reincarnated as a human. [ 146 ] In Islamic tradition, the year 570, when the Prophet Muhammad was born, is known as the Year of the Elephant . [ 147 ] Elephants were thought to be religious themselves by the Romans who believed they worshipped the sun and stars. [ 139 ]

Sri Maha Laxmi oleograph

Elephants are ubiquitous in Western popular culture as emblems of the exotic, especially since—as in the giraffe , hippopotamus and rhinoceros —there are no other animals familiar to Western audiences like them. [ 148 ] The use of the elephant as a symbol of the US Republican Party began with an 1874 cartoon by Thomas Nast . [ 149 ] As characters, elephants are most common in children's stories, in which they are generally cast as models of exemplary behavior, and include some of this branch of literature's most iconic characters. Elephants in fiction are typically surrogates for humans and their concern for the community and each other is depicted as something to which to aspire. Many stories tell of isolated young elephants returning to a close-knit community, such as "The Elephant's Child" from Rudyard Kipling 's Just So Stories , Disney 's Dumbo and Kathryn and Byron Jackson's The Saggy Baggy Elephant . Other elephant heroes given human qualities include Jean de Brunhoff 's Babar , David McKee 's Elmer and Dr. Seuss 's Horton . [ 148 ]

Several cultural references emphasize the elephant's size and exotic uniqueness. For instance, a " white elephant " is a byword for something expensive, useless and bizarre. [ 148 ] The expression " elephant in the room " refers to an obvious truth that is ignored or otherwise unaddressed. [ 150 ] The story of the " Blind men and an elephant " teaches that reality may be viewed by different perspectives. [ 151 ]

Véase también

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Otras lecturas

Enlaces externos