Julie Meachen, an assistant professor of anatomy at Des Moines University, has found bones from bison, ancient massive wolves and the American cheetah in her three years excavating Wyoming’s Natural Trap Cave.
But this past summer, her last planned to work at the site, it was dirt that had the vertebrate paleontologist most excited. She collected soil samples from different time periods going back about 30,000 years. And while it might not seem as exciting as the mammoths and short-faced bear discovered in the cave in the 1980s, the dirt could provide scientists with a better understanding of how the climate changed over thousands of years and how those changes impacted the animals that called what is now Wyoming home.
Natural Trap Cave near Lovell is named for the natural trap the landscape’s gentle incline creates by hiding a hole that drops 90 feet into a cave. Unsuspecting animals, like predators chasing prey, wouldn’t see the cave entrance until it was too late. The site, managed by the Bureau of Land Management, was first excavated in the 1970s and 1980s when paleontologists famously discovered bones of lions, cheetahs, bears and even a full mammoth skeleton. The cave was sealed in the 1980s when excavations ended. No one worked at the site for about 30 years.
Meachen and her colleagues began work at the site in 2014 and planned to examine large animal fossils to research genetic variations and how they tied to climate change. But it was the microfauna remains — lizards, snakes and rodents — that captured her interest. Previous excavators hadn’t created a detailed record of microfauna so the abundance of the small animals was a surprise and, Meachen realized, also an opportunity.
Small land-based creatures can’t travel long distances and must focus on constantly eating to survive. As such, they tell the story of long-term climate better than larger mammals that can migrate, Meachen said. Microfauna have to change if the environment changes, she said.
“They adapt or die,” she said.
This summer Meachen and her collaborators “painstakingly and systematically” collected dirt from different layers of sediment in the cave. She hopes to have collected samples that span tens of thousands of years to use for environmental reconstruction, or recreating through modeling, what the climate and environment was like in the area over time.
“We want to know how the climate changed over the last 30,000 years and what affect did it have,” Meachen said.
The samples have been sent to Georgia Tech University where researchers will sift the sediment in search of bones and teeth from rodents, rabbits, shrews, weasels, lizards, snakes and any other small creatures that died in the cave. Paleontologists at Georgia Tech also will identify the animals found, to the genus level, if not the specific species, Meachen said.
Looking at how the microfauna changed, what survived and what went extinct can provide clues to changes in the environment and how certain animals adapted.
This is the final summer Meachen planned to work at Natural Trap Cave, due to funding, but her work will continue with what she found.
“I wish I could tell you we found some giant mammoth this summer,” Meachen said.
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But the dirt, and the bones of the small animals in it, could offer significant information on the past, and also help predict how species will adapt in the future.
Work to reconstruct the environment at the time could take five or six years, Meachen said. Once researchers have cleaned, studied and recorded the specimens they find, they will be sent to the University of Wyoming for storage.