Elephant fashion show

What can make a four-ton mammal a most sensitive beast?

Mobile, prehensile, sensitive, and strong, an elephant trunk in action appears to be surprisingly independent of the rest of the animal, at times almost as though it were a separate beast. This unusual hallmark feature surely helped elephants and their ancestors--collectively the proboscideans, or trunk bearers--to adapt to diverse habitats and venture into newly available niches. Proboscidean fossils have been found on all continents except Australia and Antarctica, a distribution that indicates the animals once lived in habitats ranging from lake shores, marshes, and swamps to savannas, deserts, and mountaintops. Today two survivors remain: the African elephant (Loxodonta africana) of sub-Saharan grasslands and forests and the Asian elephant (Elephas maximus) of mixed habitat zones in India, Sri Lanka, and parts of Southeast Asia.

Just how did proboscideans develop this most versatile appendage? In his Just So Stories, Rudyard Kipling gave young readers a vivid tale of a crocodile pulling on the once-short nose of an elephant until it stretched to become the longest of animal snouts, but the evolutionary history of the proboscis is just as intriguing. The late paleontologist Alfred Romer called proboscidean history "one of the most spectacular stories in mammalian evolution."

The earliest ancestors of elephants and their kin lived more than fifty-five million years ago and were the size' of small pigs. They probably did not have trunks, but some had a mobile upper lip, similar to that of a present-day tapir. During the geological epochs that followed, the proboscideans became bigger and taller, their heads increasingly far from the ground. The process of natural selection tended to favor those early proboscideans that had developed larger heads and, more specifically, elongated mandibles, or jaws, for reaching food. In some elephant forebears, the jaws were extremely long and wide and equipped with a pair of tusks (greatly modified teeth) so broad that these beasts, such as Platybelodon, are collectively known as shovel tuskers.

The trend of long-jawed proboscideans continued for millions of years until the length and weight of the mandibles posed a problem in mechanical engineering. The center of gravity of the elongated head, upper and lower tusks, and short-version trunk had shifted forward, and considerable energy was required just to support the head in an upright position. To get around this constraint, ancestral proboscideans would require shorter heads and, especially, shorter jaws, but this would leave the tall herbivores less able to reach vegetation either in high branches or on the ground. Natural selection provided the evolutionary answer. Over the generations the head and jaws became shorter and the snout, combined with the upper lip, became a long, flexible proboscis. A simplified family tree of the proboscideans depicts early members of the group with relatively short proboscises, while later representatives, such as Deinotherium and Gomphotherium, exhibit more fully developed trunks (see next page).

Fossil crania--the upper part of skulls--dating from the end of the Miocene. show that the space where the trunk emerged from the head had become large and was situated between and above the eyes, as it is in modern elephants. (In primitive proboscideans, this opening was much lower and more forward on the cranium.) Also expanded was the infraorbital canal, a bony opening that allowed for passage of large nerves that run down through the trunk. These cranial clues suggest that by about seven million years ago, elephant forebears had trunks comparable in length and structure to those of living elephants.

An integral part of my work has been the study of the evolution, family tree, and anatomy of the 160 or so species of proboscideans that lived in the past. The continued existence of two members of such a venerable tribe of mammals is of inestimable value and has led me to investigate the natural history, behavior, and anatomy of the two living elephant species. Through the Elephant Research Foundation, which I established in 1977, my colleagues and I gather and study information on all aspects of proboscideans, living and extinct, captive and wild. The trunk is just one remarkable feature of these altogether remarkable animals, and their behavior when using it is only one reason for the fascination that I and many others have with things elephantine.

The trunk of an elephant begins to develop in utero. During the earliest stages of the eighteen- to twenty-two-month gestation, the elongated snout is separated from the upper lip. As development progresses, nose and lip unite and begin to lengthen. During the first year of life, the proboscis is shorter in relation to the body than is the trunk of an adult, but the young elephant does not have mastery of this sophisticated organ. One sometimes sees young elephants stepping on their trunks and twisting them up in the air in what appears to be frustration. The trunk has many uses, and wielding it deftly takes practice.

The trunk can be used to reach Objects high above the head, even objects an elephant cannot see, and its stretching and flexing capacities give elephants easy access to plant species beyond the reach of many other animals that share their habitats. Elephants can stand on their hind legs and stretch the trunk to reach tender leaves some twenty feet off the ground. But the trunk's uses go far beyond food gathering.

The trunk is a conjoined upper lip and nose, with the nostrils running like two parallel hoses from the trunk's base down to its tip. While the mouth contributes, most breathing is done through the nostrils. Elephants also have a keen sense of smell. Within the nasal cavity are seven turbinals, scrolls of bones with sensitive tissues specialized for olfaction (dogs have only five such turbinals). A related ability is hormone detection. When a female is in estrus (or heat) or when a male is in musth (a state of increased serum testosterone), elephants can apparently detect hormones, or chemical molecules emanating from urine, feces, and secretions from the trunk, mouth, and musth glands. Once "collected," chemical information is then passed on to an organ (known in some animals as Jacobson's organ) on the roof of the mouth and conveyed to the brain for analysis. In front of the Jacobson's organ is a row of tiny pores. Known as palatal pits, these pores may also serve to enhance chemical communication and decipher molecular information brought to the trunk for inspection. In times of possible danger, when chemical cues may be airborne, a wary elephant may raise and swivel its trunk in periscope fashion.

An essential function of the trunk is siphoning water, which can be carried to the mouth for drinking or sprayed across the back with the trunk serving as a flexible showerhead. (An elephant also uses its trunk to sprinkle dust or grass on its body, presumably to protect against insect bites and ultraviolet radiation.)

Because the amount of water that an elephant can hold in its trunk had never been measured accurately, the staff of the Elephant Research Foundation wanted to pin down the statistics. An opportunity arose when the Shrine Circus visited the foundation's home state of Michigan in 1982. With the help of the elephants' keepers, and equipped with air and water thermometers, graduated cylinders, and stopwatches, we conducted our humane experiment backstage after an afternoon performance, amid a crowd of curious onlookers. Tommy (now King Tusk of the Ringling Brothers and Barnum & Bailey Circus), a 9,800-pound, thirty-seven-year-old Asian male that had not drunk for more than twelve hours, downed 56 gallons of water in just under five minutes, siphoning a maximum of 2.7 gallons per trunkful. An Asian female named Zola drank 16 gallons in eighty-three seconds with about a gallon per trunkful. Our third subject, Churchill, a small female African elephant, was restless and seemed to want to gulp the whole bucket at once. She finally consumed 8.5 gallons in less than two minutes, with trunkfuls of just under a gallon. With this experiment, we not only successfully measured water intake but also demonstrated how captive animals can, and do, contribute to scientific information.

Vocalizations originate in the larynx, but by modifying the size of the nostrils when air is passing through them, elephants can produce a range of sounds. Individual animals may even have their own "voices," or vocal repertoire. According to biologist Judith Berg, vocalization in captive African elephants, measured in hertz (Hz), or frequency of sound waves, consists of low sounds of 5 to 28 Hz (growl, rolling growl, snort, and roar) and high sounds of 357 to 570 Hz (trump, trumpet, pulsated trumpet, trumpet phrase, bark, gruff cry, and cry).