Giant lions, wolves and more found in cave
LOVELL, Wyo. — Out of the darkness of an ancient cavern near here, light is being shined on the last ice age.
“It is an impressive site for ice-age paleontology in North America,” said Julie Meachen, 38, professor of paleontology at Des Moines University in Iowa. “But with the work we’re doing now, it’s become even more consequential.”
Last spring Meachen authored a research paper showing that wolf bones recovered from expeditions by the University of Kansas in Natural Trap Cave in the 1970s were from a 25,800-year-old Beringian wolf — the first time the animal’s remains have been recorded so far south in North America.
“People always said the bones looked like a dire wolf and a modern wolf, but nobody had done any analysis,” Meachen said while relaxing in a lawn chair under an awning erected a few hundred yards from the cave. Old junipers with twisted trunks provided a wind break at the kitchen site, which was also bordered by fold-up tables, coolers and plastic tubs stuffed with food and utensils. “The first Beringian wolf wasn’t collected until 2007 in Alaska, so Kansas had it and didn’t know it.”
Out of the abyss
Natural Trap Cave begins as a 15-foot-wide black maw in tan limestone at the base of the Bighorn Mountains. The site affords an expansive view of the Bighorn Basin, Bighorn Reservoir and three mountain ranges encircling the basin. The hole opens like a funnel into a spacious cavern more than eight breathtaking stories below and accessible to researchers only by rappelling.
For thousands of years, animals plunged to their deaths into the abyss — from stilt-legged horses to 900-pound American lions three times the size of those now living in Africa. The bones of those animals — most of which are now extinct — have been preserved in the refrigerator-like climate of the cave just waiting for someone like Meachen to come along and tease out their story.
“It’s probably the coolest project I have worked on in my life,” said geologist Gretchen Hurley, of the Bureau of Land Management’s Cody Field Office.
The BLM oversees work in the cave, which is blocked from public entrance with an iron grate.
In the past two years, Meachen and several colleagues have spent a portion of their summers extracting fossils from Natural Trap Cave. This year that work was expanded to the collection of soil samples to identify pollens to determine what plants were growing at different time periods.
“The pollen probably goes back 125,000 to 3,000 years — the late Pleistocene to early Holocene,” said Cory Redman, 36, a post-doctoral student at Des Moines University.
The pollen will show the extent of the climatic shift, Redman said.
“We have really good age control because we have three different volcanic ash beds that can be dated,” he said. “Very rarely do you have that kind of age control.”
He also noted that unlike removing fossils from rock, where only one organism may be represented, the cave’s soil provides large vertebrates, small vertebrates and pollen all in one place.
“On top of that, we have isotopic data,” Redman said.
Pennilyn Higgins, a geochemist at the University of Rochester, specializes in extracting information from ancient teeth. The isotopic analysis gives clues to shifting weather patterns and animal diets.
More oxygen isotopes indicate warmer weather. Like rings in a tree, the isotopes show the pattern of summer and winter.
“What we’re seeing so far is that it was cold,” she said. “We can’t get the exact temperature, but it wasn’t above 20 degrees Celsius (68 degrees).”
The team also is extracting small bone samples from some fossils to analyze the DNA. Natural Trap Cave is unusual in that it is cool and dry enough to preserve ancient DNA.
“It’s almost impossible to get good DNA from the tropics,” said Kieran Mitchell, an ancient DNA specialist who traveled all the way from Australia to collect samples from the cave for analysis.
“The DNA analysis will tell us how animals are moving around in the last ice age,” he said.
Of main interest to scientists is movement north and south by animals since huge glaciers would occasionally block off access between Alaska and the lower 48 states.
The DNA analysis can also tell scientists about the genetic diversity of animals, which speaks to population size. Analysis of smaller unidentifiable fossils will tell the researchers what those species were.
Mitchell was wearing a T-shirt that read: “For those who are about to become rocks, we extract you.” It plays off the Australian rock group AC/DC’s lyrics: “For those about to rock, we salute you.”
A group came in two weeks ago to survey 90 percent of the cave to map its dimensions. That work could show if there was ever another entrance to the cave that was blocked off, as well as define the three-dimensional structure of the cave.
“It probably developed within the last million to 500,000 years,” said the BLM’s Hurley. “It’s constantly enlarging as water erodes the main walls.
“That will tie in to the cave’s history, its formation, how it ties in to other caves in the area and possibly new fossil finds,” she added.
The end result of so many different examinations of one dim, cold area should produce a much clearer picture of the last ice age, climate change and the eventual extinction of numerous species in the region.
“We’re just hoping we’ll get a better understanding of how things changed over time,” Meachen said.
Like Meachen’s examination of the University of Kansas bones that led to her identification of the Beringian wolf, the samples collected by her team could someday lead to other discoveries after techniques and technology have advanced.
“Thirty years from now or 50 years from now, someone could look at the same collection and find new stuff,” Redman said. “As long as the data is well preserved, there’s a lot you can do with stuff collected 30 or 100 years ago.”