A tusk to the brain probably wasn’t what humans had in mind when they coined the term “all’s fair in love and war,” but that’s exactly what one male mastodon received while competing during mating season. His loss is however academia’s gain, as the recovery of 13,200-year-old remains has revealed – for the first time ever – the migration behavior of an individual extinct animal.
"The result that is unique to this study is that for the first time, we've been able to document the annual overland migration of an individual from an extinct species," said University of Cincinnati palaeoecologist Joshua Miller, first author on a new study published in Proceedings of the National Academy of Sciences.
The battle-scarred mastodon is known as Buesching and is an 8-ton adult that was recovered from a peat farm near Fort Wayne in the state of Indiana, US, in 1998. It died from being punctured in the right side of its skull by another mastodon’s tusk tip, but researchers behind the new paper don’t believe its final resting ground to have been its home turf.
Buesching’s banana-shaped tusk, stretching to just short of 3 meters (9.5 feet), was carved up with a bandsaw to uncover the clues that would lead them to this animal’s annual migration activities. Doing so enabled University of Michigan palaeontologist and study co-leader Daniel Fisher to extract a thin, lengthwise slab from the center of the animal’s tusk for isotopic and life-history analyses.
Mastodons were large herbivores that foraged on foliage and the chemical signatures of the foods they ate are not only indicative of the climate but also committed to record as isotopes within the animals’ tusks. This study specifically used strontium and oxygen isotopes in tusk growth layers to recreate Buesching’s adventures and environments, from an adolescent to his final years.
Using new modeling techniques and “a powerful geochemical toolkit,” they were able to reconstruct the landscape the animal occupied throughout his 34-years-long life, with the tusk segment acting like a diary of the changing conditions in which the mastodon lived.
"You've got a whole life spread out before you in that tusk," said Fisher. "The growth and development of the animal, as well as its history of changing land use and changing behavior—all of that history is captured and recorded in the structure and composition of the tusk.”
It seems Buesching’s home turf was closer to central Indiana, but he probably trekked the 160 kilometers (100 miles) to where his remains were recovered in northeast Indiana in pursuit of a mate. Indeed, the tusk fragment revealed that – like modern-day elephants – Buesching’s environment was pretty much the same until he reached adolescence at which point, he was probably booted out of his female-led herd.
After some time wandering alone, the analyses indicate Buesching started making annual trips to northeast Indiana, doing so at least three times before he died. The researchers suggest this spot might have been his preferred summer mating grounds, sort of like Spring Break.
"We've been able to show that large male mastodons like Buesching migrated every year to the mating grounds,” said Miller.
"Every time you get to the warm season, the Buesching mastodon was going to the same place—bam, bam, bam—repeatedly. The clarity of that signal was unexpected and really exciting."