Tusks of Fred the juggernaut reveal a life of fighting and roaming

More than 13,000 years ago, an American juggernaut roamed what is now the American Midwest. Year after year, he returned to an area of ​​northeastern Indiana considered mating ground. It was there that he died in battle.

Where the behemoth spent its life and how it died were all discovered by studying the chemical signatures recorded in its tusk, scientists reported Monday in the Proceedings of the National Academy of Sciences. Their techniques offer new insight into one of the many ancient relatives of elephants that roamed North America before becoming extinct.

Scientists have studied the Buesching mastodon, named after the family farm where it was found in 1998, and now on display at the Indiana State Museum. Also known as Fred, his tusks, like those of modern elephants, record an animal’s entire life history and allow scientists to glean information about specific days, weeks or years. Thus, the scientists were able to specifically sample areas of its tusk from its adolescence and adulthood and determine how its migration changed over time.

This migratory detective work focused on strontium and oxygen isotopes in tusks. Joshua Miller, a University of Cincinnati paleoecologist and study author, described strontium isotopes as leaving signals all over the landscape.

Strontium isotopes seep from the rocks into the surrounding soil and water. As plants take in these nutrients, they incorporate “those isotopic signatures,” he explained. Our hungry juggernaut would come and eat those plants, marking that geographic imprint in its tusks.

Interpreting these geographic references and matching them to the landscape requires an additional step: a map of how strontium isotopes change in the field. The authors relied on the work of other scientists, including Brooke E. Crowley, also from Cincinnati and one of the study’s co-authors, who had created such a map.

Oxygen isotopes helped discover the seasons in which Fred migrated. Whenever it rained, atmospheric isotopes recording the season were incorporated into local bodies of water and ingested when drinking from nearby ponds and streams.

With complex statistical modeling, the team was able to determine the movement of this animal.

Things changed drastically for this juggernaut from its 29th to 32nd year. As a result, he was moving over great distances with signs of repeated injuries. But he returned every year to northeastern Indiana — a place, the authors note, he never explored during his teenage years. There, in late spring and early summer, he suffered injuries, an important clue that this might be a mating ground.

Daniel Fisher, a paleontologist at the University of Michigan and also author of the study, explained that the pitting on the surface of a mastodon’s tusk is just one of the marks left by wounds. These wounds also leave an internal mark.

“It turns out that these pits form in places where the tusk, at some point in its growth history, got stuck in the back of its bone cavity,” Dr. Fisher said. When male proboscideans push their tusks at their opponents, the tusk gets stuck in the socket where it pushes out of the skull. This affects the internal growth of the defense, leaving signs of the season in which the injury occurred.

The fact that these wounds consistently recur in spring and summer in an adult male mastodon led the team to suspect that it was going through musth, a period of aggression associated with reproduction seen in modern male elephants, where fights with other males are frequent.

The fatal craniofacial injury he suffered took place during that same season on that same mating ground.

“The methods they are using are part of a larger trend in quaternary vertebrate paleontology to add much more detail to the behavior and ecology of these animals,” said Chris Widga, vertebrate paleontologist and curator in head of the Gray Fossil Site. in Tennessee, who did not participate in the research. “And this is the first time we’ve had this data, which is really, really good.”

Whether migration patterns and injuries are representative of all male American behemoths is a question for future research. The team hopes to study more male and female mastodon fossils.

For now, the study opens the door to other questions: How do the migration patterns of female mastodons differ? Were there separate breeding grounds for the different proboscideans that coexisted at that time? Or, Dr. Miller pondered, “Did they go to the same place, and it’s just a crazy region of hormone-laden proboscideans?”

Whatever the broader possibilities regarding mastodons as a species, Dr Miller backtracked on the team’s findings regarding the Buesching specimen.

“To be at a point in geochemistry and modeling and paleobiology in general where we can start to capture some of these fundamental aspects of the biology of an individual,” he said, “I think it’s so deeply, deeply exciting.”

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