Rare Mammoth Tracks Reveal an Intimate Portrait of Herd Life Read
The dinner plate-sized impressions were barely discernible. When he first spotted them in the dust of the dry lakebed, paleontologist Gregory J. Retallack and his students didn’t think much. But upon closer inspection, what looked like four or five prints partially covered in sand turned out to be a winding section of 117 tracks. These tracks, they would later learn, were left 43,000 years ago by six Columbian mammoths: four adults, a youngster and an infant on a curious journey.
This was a big deal—a mammoth one, you might say. Aside from studying living elephants, most of what we know about mammoths from physical characteristics to diet, comes from their skeletal remains. Yet social behavior is more challenging to tease out, and ancient trackways are one of the few windows in. These prints had captured an intimate moment between an injured adult female and concerned young, offering an unprecedented peek into the world of mammoth herd life.
The group came upon the tracks in April 2014, during the annual fossil hunting trip Retallack organizes for his students at the University of Oregon. They had already found fossils at several sites when he decided to swing by Fossil Lake. This dry, barren lakebed is known for its fossil riches; the remains of creatures up to 646 thousand years linger in its dusty layers, including birds, fish, mollusk and even mammals like camels, ground sloths and mammoths.
Retallack, the director of paleontological collections at University of Oregon’s Museum of Natural and Cultural History, had just instructed the class to spread out and begin their search when he spotted the circular marks. “Those look like mammoth tracks to me,” Retallack recalls telling the students standing nearby.
The students weren’t so impressed. “I don’t think they even believed me,” he says now. But the tracks stuck in his mind.
Three years later, Retallack obtained the funding to return with a team of researchers from the university, the Bureau of Land Management, and the University of Louisiana at Lafayette to unearth and analyze the prints. They dusted away the sand and, using both ground-based and drone-mounted cameras, took detailed images of the area. By compiling these images, the team created a three-dimensional digital model to tease out the elephant vignette recorded in mud. The researchers also dug a pit nearby to study the sediment layers, publishing their findings earlier this month in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.
Their analysis suggests that the creatures were Columbian mammoths, a species that tromped from Canada to modern Nicaragua starting nearly a million years ago. Standing slightly taller than modern African elephants, the creatures had massive tusks up to 16 feet long. Unlike their wooly cousins, Columbian mammoths are thought to have sported a much more sparse coat of fur—perhaps even only having a mop top of coarse hair on their heads. They are believed to have gone extinct some 10,000 years ago, though the exact cause of their demise remains a mystery.
The main trackway at the site extends for 65 feet. But there’s something strange about it: Unlike other known ancient mammoth trails, the footprints are closely spaced and the right side is much deeper than the left; the left rear foot tracks are particularly faint. “We know a lot about elephant tracks. We have a lot of them going back in the fossil record going back 16 million years or more,” Retallack says. “Mostly the elephants are striding out like a sergeant major in a parade.”
Not these pachyderms. The unusual footprints, the researchers believe, are due to an injury in the animal’s left rear leg that caused the animal to move slowly and limp, in an effort to ease the pain.
That’s an impressive amount of information to draw from one set of tracks. But Lisa Buckley, a vertebrate paleontologist at the Peace Region Palaeontology Research Centre in northeast British Columbia who specializes in interpreting ancient animal tracks, agrees. The consistency of the surface around the footprints, she says, suggests that the unusual spacing and differences in depth were from the track maker’s hobbled stride, rather than variation in the mud itself.