The entire life in a tusk: A research team succeeds in tracing the life of a male American Mastodon based on a bone find. Traces point to fights with other bulls - and certain elements reveal something about his whereabouts.
Researching the lifestyle of extinct animals is not easy - after all, researchers cannot lie in wait with a camera and simply observe them. They often only have a few bone finds left for their conclusions. However, by analyzing a tusk, a research team is able to find out about the migration and other behavioral patterns of a species of mammoth that lived more than 10,000 years ago.
The study details the life history of an American Mastodon (Mammut americanum) that lived about 13,200 years ago in what is now northern United States. The bull apparently died during the mating season in a fight with a fellow animal, as the team led by Joshua Miller from the University of Cincinnati in the US state of Ohio writes in the "Proceedings" of the US National Academy of Sciences ("PNAS").
The well-preserved remains of the mastodon were found in 1998 in northeastern Indiana. According to the analysis, the eight-ton bull died at the age of 34. A wound in the skull indicates that it was pierced by another bull's tusk - presumably while fighting for mates.
To determine the animal's life history, the team took samples from the right tusk, which was particularly large at around three meters long. "All life is contained within this tusk," said co-author Daniel Fisher of the University of Michigan at Ann Arbor in a statement. "Growth and development are incorporated into the structure and composition as well as its history, behavior and changing land use."
Because over the course of their lives, the animals store elements such as strontium and oxygen ingested with their food in the constantly growing tusks, with the oldest residues being at the top. Based on the ratios of different strontium variants - so-called isotopes - to each other, the team determined the whereabouts of the bull. The oxygen isotopes, on the other hand, provide information about the season of their storage.
In total, the team analyzed 36 samples from the first years of life and 30 more from the last phase of the bull's life. This lived in a warm phase at a time when humans had already settled North America. Accordingly, the growing animal remained with its herd until the age of 12, probably in the center of what is now Indiana. Only then did the bull expand its radius of action considerably - in seasonal cycles.
In the winter it resided more in what is now central Indiana, while in the spring and early summer it migrated north—apparently to the mating region some 100 miles (160 km) from its winter home. That's where he finally died. According to the researchers, the tusk contains evidence that the bull fought fights at least during the last eight years of his life and always in spring or early summer - presumably with other bulls for females.
As an adolescent, however, the animal avoided this region, the team writes, possibly to avoid conflicts with older bulls. According to the analysis, the bull covered almost 30 kilometers a month during its hikes - significantly less than male African elephants, which can cover hundreds of kilometers in a month in Namibia, for example.
A year ago, researchers presented the life of a woolly mammoth (Mammuthus primigenius), which lived in Alaska around 17,000 years ago, based on a tusk analysis in the journal "Science". This bull died in late winter at the age of about 28 - probably from starvation. Mastodons and mammoths lived around the same time, but are not closely related.