Prehistoric Elephant Herd
Illustration courtesy Mauricio Antón
A lone bull walks away from a Stegotretrabelodon herd in an illustration based on new analyses of seven-million-year-old footprints.
Stegotretabelodon is a primitive elephant that was roughly the same size as a modern-day African elephant—although Stegotretabelodon males had two sets of tusks (as seen above).
Fossil evidence shows that the giant beasts were once widespread in the Arabian Peninsula, including the present-day United Arab Emirates (UAE), where the tracks were found. (Also see "Huge New Dinosaur Trackway Found in U.S.")
Though scientists can't be sure the ancient tracks were left byStegotretabelodon, it's the most likely scenario, considering the animals' former abundance in the region, said study co-author Brian Kraatz, an assistant professor of anatomy at Western University of Health Sciences in Pomona, California.
Scientists had previously discovered the tracks and published a preliminary report, Kraatz said. For the new study, the team deployed a camera-equipped kite that took the first photographs of the footprints from the air. From those images, the researchers stitched together a detailed photomosaic of the trackway—one of the largest known in the world, according to the study, which was published February 22 in the journal Biology Letters.
Kraatz recalled seeing an early version of the mosaic after arriving at his hotel in the UAE late one night.
"As soon as I sat down and looked at [the mosaic], it was instantly obvious it was a herd of elephants walking together," he said. "When you see it from the air, it just crystallizes."
—Christine Dell'Amore
Aerial Footprints
Image courtesy Bibi et al
A closeup of the aerial photomosaic shows the main section of the trackway, which has given the team "astonishing glimpses into animal behavior," Kraatz said.
For instance, the scientists could tell the tracks were made by elephants of different sizes, based on the lengths of the animals' strides. (See "First Dinosaur Tracks Found on Arabian Peninsula.")
The main trackway was made by a herd of 13 animals of varying ages, the study says. Tracks from a single, large individual cross the main trackway—most likely made by a male Stegotretabelodon. This suggests that the prehistoric elephants traveled in herds of females and juveniles, while males traveled solo.
This scenario jibes with the social structure of modern elephants: Adult females lead the herds while sexually mature males live alone and return to the herd only to mate.
Footprint Cleaning
Photograph courtesy Mark Beech
Study co-author Faysal Bibi brushes sand from a footprint on January 13, 2011. The tracks are located on an exposed area of carbonate—a type of limestone—that had been scoured clean over time, making the footprints easy to spot from the air, Kraatz said.
Though this part of the Arabian Desert is now mostly sand dunes, a system ofrivers once supported a thriving diversity of African-like animals, which started dying out when the water dried up about six million years ago.
(See "Oldest Land-Walker Tracks Found—Pushes Back Evolution.")
On the Move
Photograph by Michael Poliza, National Geographic
A herd of African elephants traverses Damaraland, Namibia, in an undated picture. Like this modern-day group, the prehistoric Stegotretabelodon herd was made up of animals of various ages, including a calf, according to the team's analyses of the animals' strides.
Though Kraatz and colleagues weren't surprised to find that the ancient beasts moved in herds, the study provides the best evidence to date of the behavior in prehistoric elephants, he said.
(See "Ancient Elephant Ancestor Lived in Water, Study Finds.")
Separating From the Herd
Illustration courtesy Mauricio Antón
A simulated view of the trackway site shows a Stegotetrabelodon male walking away from the main herd. The male's 850-foot-long (260-meter-long) track suggests that the ancient elephants segregated themselves by gender, just as their modern counterparts do today.
Unlike bones, which give scientists mostly physical clues about ancient animals, tracks are "fossilizing an aspect of the way they lived," Kraatz said.
(See "Elephants Took 24 Million Generations to Evolve From Mouse-Size.")
Isolated Track
Photograph courtesy Faysal Bibi
A person walks near part of the male Stegotetrabelodon's trackway on January 13, 2011.
Overall, Kraatz said, the research gives scientists new insight into a species loved by many. (See elephant pictures.)
"We're strongly attached to elephants," he said, "and it's cool we can trace this [herding] behavior back so many millions of years."
Next: Photos: "Dramatic" Elephant Rescue in Zambia >>
Photograph courtesy Abraham Banda, Norman Carr Safaris
Published February 23, 2012
National Geographic
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