MAIN ELEPHANT FEATURES: TUSKS, TRUNK AND EARS

ELEPHANT TUSKS

Asian elephant in Cambodia in 1903

Elephants have deeply rooted tusks protruding from their mouths that grow continuously. These tusks are actually enormous teeth that give the pachyderms an evolutionary advantage when digging, lifting objects, stripping bark of trees and protecting themselves.

Tusks are hollow upper incisors used by elephants to move and lift objects and male elephants to fight. Ivory is the white dentin of which tusks are made. The largest tusks weigh as much as a man and measure twice as long. Asian elephants tusks are considerably smaller than the ones on African elephants. Tusks grow continuously; an adult male's tusks grow about 18 cm (7 in) a year. The tusk cavity of one Asian elephant still hadn’t healed 16 years after it was hacked off by poachers.

Tusks are used to dig for food and water, to dig up trees and branches and move them around, for self defence and for sexual display. In males, tusks are often used to intimidate other males, and sometimes in fighting for mates. Those with the biggest tusks are usually the most successful.

How Elephants Got Their Tusks

The earliest known tusks are found in Dicynodonts, a group of stocky, pig-like herbivores that lived 270 million years ago and had unique pointed beaks with protruding teeth on either side. According to Live Science: Members of this clade with true tusks were also missing several teeth. Researchers theorized that it may have been more energetically favorable to develop tusks that continuously grow, rather than replacing teeth that may have fallen out. They also suggested that the tusks evolved independently in different populations over time. When the tusks developed, soft tissue ligaments formed, anchoring the large teeth to the jaw. [Source: Elise Poore, Live Science, January 6, 2024]

According to a study published in October 2021 the journal Proceedings of the Royal Society B, it takes two key adaptations to teeth to make a tusk — and the evolutionary pathway first appeared millions of years before the first true mammals. Asher Elbein wrote in the New York Times: “Around 255 million years ago, a family of mammal relatives called dicynodonts — tusked, turtle-beaked herbivores ranging in stature from gopher-size burrowers to six-ton behemoths — wandered the forests of the supercontinent Pangea. A few lineages survived the devastating Permian extinction period, during which more than 90 percent of Earth’s species died out, before being replaced by herbivorous dinosaurs. “They were really successful animals,” said Megan Whitney, a paleontologist at Harvard University and lead author of the study. “They’re so abundant in South Africa that in some of these sites, you just get really sick of seeing them. You’ll look out over a field and there’ll just be skulls of these animals everywhere.”[Source: Asher Elbein, New York Times, October 29, 2021]

Early elephant relatives had enlarged canines that were covered with enamel, Whitney said. Later members of the family reduced the enamel to a thin band on one side of the tooth, like a rodent incisor, allowing the tooth to grow continuously. Finally, they ditched the enamel entirely. “You’re providing the means for a tusk to evolve if you unlock the evolution of reduced tooth replacement and soft tissue attachments,” Whitney said. “Once you have a group that has both conditions, you can go a long time of animals playing with different tooth combinations, and you start to see these independent developments of tusks.”

Elephant Tusks Getting Smaller Because of Poaching and Evolution

Richard Gray wrote in The Telegraph, “Elephants are evolving smaller tusks due to pressure from hunting and poaching for ivory, according to conservation experts. The average tusk size of African elephants has halved since the mid-19th century. A similar effect has been spotted in the Asian elephant population in India. Researchers say it is an example of Darwinism in action, caused by the mass slaughter of dominant male elephants - but whereas evolution normally takes place over thousands of years, these changes have occurred within 150 years. [Source: Richard Gray, The Telegraph, January 20, 2008]

Zoologists at Oxford University fear that poaching and hunting of the largest male elephants, which also have the largest tusks, has changed the natural breeding behaviour of these animals. Their research has shown that the hunting of these large males for their ivory allows smaller males with shorter tusks to produce more calves. Over time the average tusk size decreases.

Iain Douglas Hamilton, from the conservation charity Save the Elephants and who was one of the authors of the study, said: "What appears to be the case is that average tusk sizes have decreased greatly since the mid-19th century. The data comes from the trade statistics and from records of hunters around Africa who find that large trophies are very much harder to find. "While some of this may be due to an absence of older animals, it is possible there has been a genetic selection pressure against large tusk size that outweighs their usefulness in contests with other males in winning females."

In males, tusks are often used to intimidate other males, and sometimes in fighting for mates. Those with the biggest tusks are usually the most successful. But the ivory of large African elephants is particularly prized by hunters and traders for its quality and this has seen hundreds of thousands of animals killed.

Tuskless Elephants

An increasing number of elephants have no tusks, according to a survey. Research at the Queen Elizabeth National Park, Uganda, showed that 15 percent of female elephants and 9 percent of males in the park were born without tusks. In 1930 the figure for both male and female elephants was only 1 percent. They say elephants are losing their tusks as a rapid and effective evolutionary response to escape slaughter by ruthless and resourceful poachers who kill elephants for their ivory trophies. [Source: BBC, September 25, 1998]

Asian trunk

The number of tuskless elephants has more than doubled to 90 percent in Sri Lanka The trait grew from two percent to 38 among one population in Zambia and 98 percent in a South African one. With the dominant elephants, with the biggest tusks, killed by poachers, “losers do more breeding and thretane the viability of the species.

The BBC's Science Correspondent, John Newell, says the continuing change shows how rapidly evolution can react in response to pressures that threaten the survival of a species. This allows them to live, breed more freely and produce more offspring without tusks. Evidence of a trend in tuskless elephants has been reported elsewhere. Mark and Delia Owens recorded an unusual number of such elephants in 1997 while carrying out research in Zambia's North Luangwa National Park. Published on the National Wildlife Federation's Website, they write: "Our research indicates that more than 38 percent of Luangwa elephants carry no tusks. "Other researchers have reported that in natural, unstressed populations, only 2 percent of the animals are tuskless."

In 2005, Reuters reported; “Chinese elephants are evolving into an increasingly tuskless breed because poaching is changing the gene pool, a newspaper reported. Five to 10 percent of Asian elephants in now had a gene that prevented the development of tusks, up from the usual 2 to 5 percent, the China Daily said, quoting research from Beijing Normal University . "The larger tusks the male elephant has, the more likely it will be shot by poachers," said researcher Zhang Li, an associate professor of zoology. "Therefore, the ones without tusks survive, preserving the tuskless gene in the species." Since only male elephants have tusks, there were now four female elephants for each male in , up from the ideal ratio of two, the paper said. [Source: Reuters, July 19. 2005]

Elephant Trunks

Implausible marvels of evolutionary biology, elephant trunks are strong, dexterous and flexible. They can be more than two meters (6.5 feet ) long and have more than 40,000 individual muscles and nerve fibers. They are capable of lifting over 270 kilograms (600 pounds) but can carefully pick up a single peanut. [Source: Jacklin Kwan, Live Science, December 7, 2023]

An elephant's trunk is an upper lip and nose joined together with two hose-like nostrils running its entire length. There are over 50,000 individual muscles and a complex network of blood vessels and nerves in an elephant's trunk. The end of the trunk is covered with sensory hairs that feel the shape, texture and temperature of things. Elephants do most of their breathing through their trunks and have extremely strong senses of smell. [Source: Jeheskel Shoshani, Natural History, November 1997]

According to a Rudyard Kipling story, elephants acquired their trunks one day when a crocodile grabbed on to a short-nosed elephant and kept pulling and pulling. An elephant using it trunk and standing on its hind legs can reach objects that are 40 feet off the ground.

Elephants are so dexterous with their trunks they have been observed picking up a dime off a concrete floor. Young elephants have to learn to use their trunks. Those that haven't yet mastered their trunks, steep on them, flail them about without control,

Trunk Uses

African trunk

Elephants use their trunks to pick up things, drink, reach food over their head, bring food to their mouths, dig wells, root for tubers, spray water and dust, greet other elephants and chase other animals away. Lame elephants sometimes use their trunks as crutches.

Adult elephants drink by siphoning water into their trunk, taking in as much as a 2.7 gallons at one time, and then squirting it into their mouths. Elephants drinking in this way have been observed drinking16 gallons in 83 seconds and 56 gallons in five minutes. Only young elephants drink water from a water hole with their mouth. Elephants also use their trunks to spray their bodies or the bodies of other elephants with water.

Some elephants use their trunks as snorkela when the go swimming and have been observed using them as snorkels in mud pits. Young elephants learning to spray themselves with water miss as often as they hit. One young elephant that was just learning how to do this kept getting his trunk stuck in the riverbed.

See Social Behavior

How Elephants Got Their Trunks

Jacklin Kwan wrote in Live Science: The exact environmental and biological pressures that led to the evolution of these trunks have long puzzled scientists, but a new preprint study, published November 28 in the journal eLife reveals that climate-driven changes may explain part of the mystery. Understanding the evolution of elephant trunks has always been challenging because the soft tissues of the trunk, like muscles and skin, do not fossilize well. This makes it difficult for scientists to find direct evidence of early forms of the trunk in fossil records.[Source: Jacklin Kwan, Live Science, December 7, 2023]

Many long-trunked animals have long lower jaws, the scientists explained. But these long mandibles subsequently shorten after co-evolving with a trunk — though the link between the two is somewhat unclear. In the new study, researchers compared three major families of elephant-like mammals in northern China that existed around 11 to 20 million years ago, investigating how the physiology of these groups differed depending on their feeding strategies and ecosystems.

The groups included Amebelodontidae, Choerolophodontidae and Gomphotheriidae — three distinct lineages of gomphotheres, the ancestral group of living elephants. The lead author of the study Chunxiao Li, a researcher at the University of Chinese Academy of Sciences, told Live Science that these ancient mammals were of particular interest because they all had long but "differentiated" mandibles, so could infer how it impacted trunk evolution.

The team analyzed the tooth enamel of these three types of early elephant to glean new clues about their feeding habits and the environments they lived in. They found that Choerolphontidae seemed to live in relatively closed environments like forests, while Amebelodontidae expanded into more open habitats, such as grasslands. Gomphotheriida appeared to have lived in habitats that were somewhere in between.

The scientists combined these findings with mathematical simulations of the jaw motion of these three extinct species. "Cherolophodon live in dense forests, so there are many plants that have horizontally extending branches," study co-author Shi-Qi Wang, professor at the Key Laboratory of Vertebrate Evolution and Human Origins at the Chinese Academy of Sciences told Live Science. Their jaws were suited to exerting pressure in up and down directions, rather than forwards or backwards, efficiently cutting through horizontal foliage. The researchers suggested their trunks were relatively primitive and clumsy.

However, the jaws of both Gomphotheriida and Amebelodontidae, which lived in more open habitats, were more adapted to cutting vertically growing plants like soft-stemmed herbs and grasses. The nasal area of their skulls seemed to more closely resemble modern elephants, suggesting their trunks were capable of coiling or grasping actions that could help bring food directly to their mouths. "We know that the whole paleo-environment changed [during this time] from warm and humid to colder, drier and open environments," Li said. "At that time, we see that these [early elephants] start using their long trunks to grab grasses." This open-land grazing may have promoted the evolution of the trunks we see today, she said. It also provides clues as to why forest-dwelling animals like tapirs have trunks that are relatively feeble compared with elephants' trunks. "We found why [early elephants] started to have such smart trunks… their trunks become stronger and more flexible, until finally, they start losing their long mandibles," Wang said.

Elephant Ears and Senses

An elephant’s large ears help it keep cool and pick up low-frequency sounds (see Below). Asian elephant are thought to have developed smaller ears because they spend most of their time in relatively cool, shaded forests while many African elephants spend their time in hotter, open country and need larger ears to help stay cool. Thermal photographic images of African elephants at night show their ears are noticeably cooler than the rest of their bodies. Ears vary so much from elephant to elephant they can be used to identify individuals.

Elephants have an acute sense of smell and very long eyelashes. Their eyesight is poor, which allows people to approach them if they are very quiet.

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated December 2024