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Mastodon tusk chemical analysis reveals first evidence of one extinct animal’s annual migration

Chemical analysis of the mastodon tusk reveals the first evidence of the annual migration of one extinct animal

University of Michigan paleontologist Daniel Fisher with the assembled skeleton of the Buesching mastodon, based on casts of individual bones produced in fiberglass, on display at the University of Michigan Museum of Natural History in Ann Arbor. Credit: Eric Bronson, Michigan Photography.

About 13,200 years ago, a wandering male mastodon died in a bloody mating season battle with a rival in what is today northeastern Indiana, nearly 100 miles from its home range, according to the first study to determine an individual animal’s annual migration from an extinct kind.

The 8-ton adult, known as the Buesching mastodon, was killed when an adversary pierced the right side of its skull with a tusk tip, a deadly wound revealed to researchers when the animal’s remains were recovered on a nearby peat farm. from Fort Wayne in 1998.

Northeast Indiana was likely a summer breeding ground for this lone hiker, who made the annual trek for the last three years of his life, venturing north from his home in the cold season, according to a newspaper slated for online publication on September 13. June in Proceedings of the National Academy of Sciences

The study also shows that the Buesching bull may have spent time exploring central and southern Michigan, which seems fitting for a creature whose full-size fiberglass-molded skeleton is on display at the University of Michigan Museum of Natural History. at Ann Arbor.

“The unique result of this study is that, for the first time, we have been able to document the annual land migration of an individual of an extinct species,” said University of Cincinnati paleoecologist Joshua Miller, the study’s lead author.

“Using new modeling techniques and a powerful geochemical toolkit, we were able to demonstrate that large male mastodons such as Buesching migrated to the mating grounds every year.”

UM paleontologist and co-research leader Daniel Fisher took part in the excavation of the mastodon in Buesching 24 years ago. He later used a band saw to cut a thin, longitudinal plate from the center of the animal’s banana-shaped, 9.5-foot right tusk, which is longer and more fully preserved than the left.

That plate was used for the new isotope and life history analyses, which allowed scientists to reconstruct changing patterns of landscape use during two key periods: adolescence and the last years of adulthood. According to the researchers, the Buesching mastodon died at age 34 in a battle for access to mates.

“You’ve got a whole life spread out in front of you in that tusk,” said Fisher, who has studied mastodons and mammoths for more than 40 years and helped unearth several dozen of elephants’ extinct relatives.

“The animal’s growth and development, 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,” said Fisher, a professor of earth and environmental sciences. , professor of ecology and evolutionary biology, and curator of the UM Museum of Paleontology.

The team’s analyzes found that the original home of the Buesching mastodon was likely in central Indiana. Like modern elephants, the young male stayed close to home until he separated from the female-led herd as an adolescent.

As a lone adult, Buesching traveled farther and more frequently, often nearly 20 miles a month, according to the researchers. Also, his landscape use varied with the seasons, including a dramatic northward expansion into a summer-only region that included parts of northeastern Indiana — the supposed mating grounds.

“Every time you came in the warm season, the Buesching mastodon would repeatedly go to the same place — bam, bam, bam. The clarity of that signal was unexpected and really exciting,” said Miller, who has used similar isotopic techniques to study the migration of caribou in Alaska and Canada.

Under harsh Pleistocene climates, migration and other forms of seasonal landscape use were likely critical to the reproductive success of mastodons and other large mammals. However, according to the new study, little is known about how their geographic range and mobility fluctuated or changed seasonally with sexual maturity.

Chemical analysis of the mastodon tusk reveals the first evidence of the annual migration of one extinct animal

The left half of the right tusk of the Buesching mastodon. Numbers on the side of the tusk (12-14) indicate where specific annual layers (counting from the tip of the tusk to the end of life at the base) are exposed on the tusk surface. Credit: Jeremy Marble, University of Michigan News.

But techniques to analyze the ratios of different forms, or isotopes, of the elements strontium and oxygen in ancient tusks are helping scientists unravel some of those secrets.

Mastodons, mammoths and modern elephants, part of a group of large mammals with flexible trunks called proboscideans, have elongated upper incisors that emerge from their skulls like tusks. In each year of the animal’s life, new growth layers are deposited on the already existing ones, deposited in alternating light and dark bands.

The annual growth layers in a tusk are somewhat analogous to the growth rings of a tree, except that each new tusk layer forms near the center, while new growth in trees occurs in a layer of cells next to the bark. The growth layers in a tusk resemble an inverted stack of ice cream cones, with time of death at the base and time of birth at the tip.

Mastodons were herbivores that browsed trees and shrubs. As they grew, chemical elements in their food and drinking water were absorbed into their body tissues, including the gracefully tapered, ever-expanding tusks.

In the newly published study, using strontium and oxygen isotopes in tusk growth layers, the researchers were able to reconstruct Buesching’s journeys as an adolescent and as a reproductively active adult. Thirty-six samples were collected from the adolescent years (during and after exit from the matriarchal herd), and 30 samples were collected from the last years of the animal’s life.

A tiny drill bit, operated under a microscope, was used to grind half a millimeter from the edge of individual growth layers, each covering a period of one to two months in the animal’s life. The powder produced during this milling process was collected and chemically analyzed.

Proportions of strontium isotopes in the tusk yielded geographic fingerprints that were linked to specific locations on maps showing how strontium changes across the landscape. Oxygen isotope values, which show pronounced seasonal fluctuations, helped the researchers determine the time of year when a specific tusk layer formed.

Chemical analysis of the mastodon tusk reveals the first evidence of the annual migration of one extinct animal

Close-up showing pieces of a mastodon tusk (not from the Buesching mastodon) owned by University of Michigan paleontologist Daniel Fisher. In Fisher’s right hand is a block close to the base of the tusk, with layers representing the last six years of life. A cross-section of a mastodon tusk tip, in Fisher’s left hand, shows concentric annual tusk layers. Credit: Jeremy Marble, University of Michigan News.

Because both strontium and oxygen isotope samples were collected from the same narrow growth layers, the researchers were able to draw specific conclusions about where Buesching traveled at different times of the year and how old he was when he made each trip.

Next, isotope data from the tusks were fed into a spatially explicit motion model developed by Miller and his colleagues. The model allowed the team to estimate how far the animal was moving and the likelihood of movement between candidate sites — something lacking in previous studies of extinct animal motion.

“The field of strontium isotope geochemistry is a really emerging tool for paleontology, archaeology, historical ecology and even forensic biology. It’s thriving,” Miller said. “But really, we’ve just scratched the surface of what this information can tell us.”

Fisher and Miller said the next step in their mastodon research project is to analyze the tusks of another individual, either another male or a female.

The other authors of the PNAS study are Brooke Crowley and Bledar Konomi of the University of Cincinnati, and Ross Secord of the Nebraska State Museum and the University of Nebraska-Lincoln.

Study takes an unprecedented look into the life of 17,000-year-old mammoth

More information:
The use of the male mastodon landscape changed with maturation (Late Pleistocene, North America), Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2118329119

Provided by the University of Michigan

Quote: Chemical analysis of the mastodon tusk reveals the first evidence of the annual migration of one extinct animal (2022, June 13), retrieved June 14, 2022 from https://phys.org/news/2022-06-mastodon- tusk-chemical-analysis-reveals.html

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