The second excavation at the Chelsea site was conducted in an effort to confirm the age of the woolly-Columbian mammoth hybrid bones found in 2015, The Ann Arbor News reported. A preliminary analysis indicates that the bones are more than 15,000 years old, the university said.
Paleontologists spent one day excavating the site in 2015 after farmer Jim Bristle discovered the bones in his soybean field. The first dig uncovered 55 to 60 mostly intact mammoth bones, accounting for 30 to 40 percent of the animal.
"It was such a hurried thing the first time around," said Bristle, who renamed his farm Mammoth Acres after the discovery. "So this is an opportunity to complete the discovery process."
The second dig prioritized reconstructing the geological context of the animal's remains, said paleontologist Daniel Fisher, who led both excavation efforts and is overseeing the analysis of the material collected.
"This return to the Bristle site was absolutely a success. We got the kind of information that we need to do the science right, and we were also able to recover an impressive amount of additional material from this animal," Fisher said. "I'm confident that as a result of this second excavation, we'll have more insight into what happened here."
Researchers have determined that the mammoth was likely a 45-year-old male. There is also evidence that the mammoth was killed by humans for food.
Bristle donated the remains to the university several days after the initial dig in 2015. Some are on display at the university's Museum of Natural History.