Scientists uncover the migration of a mastodon that died 13,200 years ago

The tusk holds the secrets.
Ameya Paleja
Graphical reconstruction of a male mastodon Sergiodlarosa/ Wikimedia Commons

Scientists at the University of Michigan have found details of annual migration that a male mastodon would regularly take in the years before his ultimate death at the age of 34, Phys.org reported. The mastodon died 13,200 years ago. 

Mastodons were elephant-like herbivorous creatures that lived in herds in North and Central America before they went extinct about 10,000-11,000 years ago. Typically between 8-10 feet (2.5 - 3 m) tall, these creatures weighed between 8,000-12,000 pounds (3,600-5,400 kg), and while climate change has also been attributed as a cause for their extinction, hunting by human ancestors has also been a major contributor.

The Buesching mastodon 

In 1998, a couple, Kent and Janne Buesching, found a mastodon fossil on their property while they were mining for peat near Fort Wayne, Indiana. When archaeologists were done with the site, they had excavated a well-preserved fossil of a mastodon that during his prime stood nine feet (2.7 m) tall and was 25 feet (7.6 m) long. 

The specimen was called Buesching mastodon, and archaeologists had then found a puncture hole on the right side of his skull, likely caused by the tusk of another mastodon during a bloody duel during a mating season. 

Daniel Fisher, one of the researchers who helped the excavation in 1998 is now a professor of paleontology at the University of Michigan as well as the director of the university's Museum of Paleontology, where the Buesching mastodon's fossilized remains are kept to be studied further. 

A team led by Fisher cut a long thin section from the Buesching mastodon's over nine feet (3 m) long right tusk to know more about the creature and his whereabouts.  

Studying Isotopes of the tusk

Like the annual rings of a tree, the tusk of an animal is also a record of its growth and development, Fisher said in the press release. Whenever the mastodon ate leaves or drank water, chemical elements from their environments got embedded into their tusks. An entire tusk is, therefore, a record of the animal life with events during birth at the tip and those near death at the base of the tusk. 

The researchers studied ratios of strontium isotopes in the tusk sample and mapped them against various locations to determine the geographies where the mastodon may have traveled to. The oxygen isotope values helped determine the seasonal changes in the creature's lifetime and the time of year the tusk was formed.

The isotopic data were then entered into a movement model specially designed by the research team to estimate how far the animal had moved. The analysis revealed that the mastodon's home was likely in Central Indiana, where he possibly stayed till his adolescence. 

As a male, the mastodon had to leave the female-led herd after reaching this age and likely traveled solo covering as many as 20 miles (32 km) each month. Interestingly, during summers, the mastodon moved to a specific location in northeast Indiana, most likely a mating ground. 

It was likely during one such season 13,200 years ago that the Buesching mastodon was struck in the head by a competing male, resulting in his death. The mastodon was 34 years old. 

The researchers have published their findings in the Proceedings of the National Academy of Sciences.

Abstract:

Under harsh Pleistocene climates, migration and other forms of seasonally patterned landscape use were likely critical for reproductive success of mastodons (Mammut americanum) and other megafauna. However, little is known about how their geographic ranges and mobility fluctuated seasonally or changed with sexual maturity. We used a spatially explicit movement model that coupled strontium and oxygen isotopes from two serially sampled intervals (5+ adolescent years and 3+ adult years) in a male mastodon tusk to test for changes in landscape use associated with maturation and reproductive phenology. The mastodon's early adolescent home range was geographically restricted, with no evidence of seasonal preferences. Following inferred separation from the matriarchal herd (starting age 12 y), the adolescent male's mobility increased as landscape use expanded away from his natal home range (likely central Indiana). As an adult, the mastodon's monthly movements increased further. Landscape use also became seasonally structured, with some areas, including northeast Indiana, used only during the inferred mastodon mating season (spring/summer). The mastodon died in this area (>150 km from his core, nonsummer range) after sustaining a craniofacial injury consistent with a fatal blow from a competing male's tusk during a battle over access to mates. Northeast Indiana was likely a preferred mating area for this individual and may have been regionally significant for late Pleistocene mastodons. Similarities between mammutids and elephantids in herd structure, tusk dimorphism, tusk function, and the geographic component of male maturation indicate that these traits were likely inherited from a common ancestor.

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