Caves whisper exploration and discovery.
Anyone who has ever set foot in a cave of any size cannot help but wonder what lies beyond, what lurks in the crevices, the darkness. Stepping into a cave is stepping into the entrance of mystery just waiting to be revealed. In a world that has been largely tamed to fit the human species, there are few spaces that still hold an element of danger. These unknown spaces beckon to the adventurous: “Explore me!” And who wouldn’t answer that call?
Me, that’s who. I am perfectly happy learning about the discoveries in caves from other people, thank you very much.
For people like me, Twitter and blogs have provided tantalizing glimpses of such explorations the world over. And one of the more fascinating adventures has taken place at Persistence Cave, just one cave of many at Wind Cave National Park, South Dakota.
“Wind Cave National Park is full of fossils. Almost everywhere you go there’s going to be fossils: in the cave and at the surface. So Wind Cave National Park actually has [perhaps] 30-40 fossil sites.”
PhD student Jeff Martin explained more about the work he and his colleagues conducted there last season as he and his wife were literally driving to Texas to begin a new chapter in their lives. He was in the moving truck; his wife was in the jeep ahead. Jeff and I had been in touch by email from time-to-time over the past year. As luck would have it, and thanks to his seemingly unending generosity, the time to discuss Persistence Cave by phone was while he was on the open road.
Wind Cave—as we know it now—was named because of the air that blows through an opening within. It was considered a sacred place to the Native Americans long before settlers knew of its existence. The Lakota people refer to the Black Hills (where Wind Cave is located) as ‘He Sapa’, (although it is listed as ‘Paha Sapa‘ on the Wind Cave National Park site). Eventually, in 1903, it became the 8th National Park, but the first one to center around a cave.
Persistence Cave, a much smaller and less-explored cave in the park, was discovered by accident by Marc Ohms, spelunker and physical science technician for the park, in 2004. His initial foray into the cave was brief: moving a cap rock, peering inside, seeing a rattlesnake, and deftly removing himself from the opening.
But its value as a fossil site was discovered thanks to another member of the park.
“Rod Horrocks, Wind Cave National Park Physical Scientist, in 2013, collected some sediment for preliminary analysis to see whether the site is paleontologically productive,” Jeff explained by email earlier.
It was, and this analysis is what eventually brought several scientists from diverse locations together.
Rod Horrocks sent the material to Dr. Jim Mead, Persistence Cave Project Leader, then at East Tennessee State University, where Jeff was a Master’s student at the time. Jeff eventually moved to the University of Maine for his PhD, where Dr. Jacquelyn Gill was his advisor.
“Sharon Holte, PhD Candidate at the University of Florida, was also a previous Master’s student of Jim’s, as well as Dr. Chris Jass at the Royal Alberta Museum,” wrote Jeff, explaining the connections between the Persistence Cave teammates. “He knows that we each excel in different aspects of vertebrate paleontology, and he invited each of us to collaborate on [and] bring our expertise into the research project. I brought Dr. Gill with me to the Black Hills to see the cave and to learn how a paleontological excavation is usually conducted. She brings a different set of skills related to paleoecology and palynology.”
Also on the team are undergraduate Chason Frost from the University of Maine who studies horticulture. His skills and those of Dr. Gill help the group understand that fossil plants and pollen found in the cave.
Sharon Holte, aside from being one of the three principal spelunkers in this dig, is in charge of educational components. Chris Bell at the University of Texas Austin studies the fossil rodents; Dr. Chris Jass and Dr. Jim Mead study fossil rodents as well, but include fossil snakes.
“Each person has their role,” he said, “their own ecological-niche, if you will.”
And Jeff? He is the “bison guy.”
“My PhD research and dissertation focuses on bison body size adaptation to climate change over the past 40,000 years and how does that evolutionary legacy influence the bison we ranch today,” he wrote before he graduated this past Spring. “To answer this, I am using Persistence Cave and other fossil sites in Wind Cave National Park boundaries to geographically isolate my variation to only local animals.”
Wind Cave National Park, currently home to 400+ extant bison, offers information on both fossil bison and their living descendants.
“Collectively, we (Jacquelyn, Chason, and I) will then also look at the pollen grains and macro-botanicals preserved in the sediment to reconstruct the paleoecology and paleoclimate of the Black Hills through the last 11,000+ years to today. This is [to understand] the climate and ecology the bison were living in at these times.”
But let’s get back to the cave itself.
Below is an image of Natural Trap Cave (another exciting fossil cave dig in Wyoming; photo from myfossil.org):
Compare that to an image of Persistence Cave from the top looking in (photo: Chason Frost as posted on Jeff Martin’s blog here):
And one of Sharon Holte peering out:
Finally, below is an image from the Rapid City Journal of “a tight spot in Wind Cave” (photo: National Park Service):
When I asked about how this image compares to the space within Persistence Cave, I was surprised by Jeff’s email response.
“The picture above is much larger than the cave we are working in,” he described of the 2015 dig. “The cave is very narrow and only fits one person’s shoulder width and up to 1.5 shoulder widths in places. The vertical height is similar to the above photo though.”
“I’m a broad shouldered fella’ and very, very tall,” he continued by phone recently. “The space in there to turn around is not quite enough for me, so I’d have to climb in and then climb backwards out.”
“Chris Jass and I are both the exact same height. Chris is a far more experienced spelunker, and even Chris wasn’t going in there.”
Sharon Holte, Chason Frost and Jim Mead were the principal spelunkers for the site. Only one person could be in the cave at a time, and their only source of light came from a headlamp. Trowels, buckets and ropes: their only tools.
“I thanked them endlessly, and I still thank them for all the work they were doing down in there,” Jeff said of his three colleagues. (A video of Sharon’s work in the cave can be found here.)
Work involved taking chunks of sediment in buckets out of the cave, tagging it, labeling the information (where that sediment appeared on the appropriate grid, at what depth, etc.), bagging that sediment, and then sending it down—by zipline, of all things!—to the truck below, where it could be taken to be screenwashed by other team members. (You can see a video of that process here, on Jeff’s blog.)
Screenshot of tweet during the 2015 Persistence Cave (#cavebison) dig
Their fossil discoveries have been diverse. Jeff wrote that “[a] camelid, (the species is unknown at this time), has been an extraordinary find. We have 5 different kinds of snakes and at least 5 different species of bats. [A] pika is also an intriguing find.”
Screenshots of some of the many tweets during the 2015 Persistence Cave (#cavebison) dig
“One of the fun things that we ran across was a ton of Ponderosa pine needles,” he mused later by phone. “That’s the primary tree out there now. Today, they’re mostly a two-needle bundle. In the past, it seems as though they were a three-needle bundle. And we don’t know exactly what that means yet. So we’re trying to figure out if that means anything at all; if it’s a genetic difference; or if it truly is an environmental difference that it’s responding to.”
Screenshots of some of the many tweets during the 2015 Persistence Cave (#cavebison) dig; the scientists involved in this dig didn’t just conduct research, they also conducted outreach to the larger public through social media.
Work did not continue as expected on the site this year for a number of reasons, but it’s not over yet. Studies on the fossils continue at the University of Maine (pollen and plants); the bison fossils have travelled with Jeff to Texas A&M University where he is now in wildlife sciences; and the rest of the fossils are housed at The Mammoth Site, where Dr. Jim Mead is currently Chief Scientist and Director.
The Mammoth Site is another major connection between many of the team members, as they have each “worked [there] at some point…over the last 40 years.”
As many know, that site is a paleontological (and proboscidean!) goldmine turned museum, thanks to the work of many, including the late Dr. Larry Agenbroad. Over 60 mammoth fossils have been discovered there to-date, among other fossil species.
Image of the bonebed at The Mammoth Site where excavations continue to this day
“He was probably THE reason that I got into the School of Mines [as an undergrad] and was also the reason I got into paleontology,” Jeff said of Dr. Agenbroad.
“I’m not alone,” he continued. “There are several of us that are like that. We all stem from Larry.”
The reverence in his voice was not difficult for me to understand.
Jeff’s introduction to this paleontologist began when he was much younger, through the 2000 documentary “Raising the Mammoth.” The film focuses on the Jarkov mammoth, and Bernard Buigues’ attempts to excavate it. The team Buigues calls upon to help include some giants of proboscidean research: Dick Mol and Larry Agenbroad.
A year or so after seeing that film, Jeff’s family traveled to The Mammoth Site. It was winter in South Dakota, and, he said, his family basically had “the run of the whole place.” With a graciousness I am sure permeates everyone who works at that site, one of the interpreters (‘docents’) offered to bring Dr. Agenbroad out to meet them.
“There’s 8-year-old me that’s just giddy with joy to be able to meet one of my idols,” Jeff shared with no small amount of enthusiasm. “And then he said, ‘You’re a little bit too young to work for me. Come back when you’re older.’”
“So that’s exactly what I did. I worked for him in [the summers of] 2007 at the Hudson-Meng Bison Kill Site and 2008 and 2009 at the Mammoth Site as an intern while I was at the School of Mines.”
“I’ve made my peace with it,” he acknowledged, and then said something that truly moved me: “I have several things that Jim [Mead] gave me…and one of them is a pocketknife that I carry on me every single day. One of the same pocketknives that Larry carried on him every single day. So I’ve got Larry with me, right now, as a matter of fact.”
Jeff and his colleagues hope to resume work at Persistence Cave next year.
As we discussed some of the findings from last year’s dig, he said, “The oldest date right now at Persistence Cave is at 39,000 and the youngest date is at 3,200. We have some 37,000 years of deposits with bison throughout. And we also have [modern-day] bison living at the surface!”
Jeff’s research, both of Persistence Cave and of Project Bison, underscore his passion for this animal, as well as the desire to understand its ecological significance.
“I’m looking at both the fossil record and looking at their body size, using the calcaneum [heel bone] as the proxy for body mass. And then also comparing that to modern bison that have just recently passed away within the past 1-3 years. That’s what I was doing this past summer: going to carcass sites and measuring their calcanea. The unique thing about Wind Cave is that they have almost every single animal microchipped. So they can track this animal throughout its life. On top of that, they bring them in once a year and weigh them. So now we have a known mass of these animals and now a known measurement, because I measured some of their calcanea.
“I’ve got some [fossil bison calcaneal] measurements that go up to 180 millimeters, and I also have Bison bison today that the longest that I’ll find are 130 millimeters. So quite a body size change in between the fossil and modern.”
Jeff presented some of his research at last year’s Society of Vertebrate Paleontology (SVP) meeting in Dallas.
Describing the results, he explained, “As it gets colder, bison get bigger. As temperatures are increasing, bison get smaller. That has modern day application to the bison industry today. If we’ll have smaller bison with future global warming, we’re going to have to change our management options.”
As I pondered all of the information Jeff had shared with me about the work he and his colleagues had done, I couldn’t help but go back to the images of how small the cave actually is. If Wind Cave National Park has an abundance of fossil sites, why go through the trouble of trying to access this one?
“Surface localities often represent a one-time event,” he explained. “Persistence Cave represents many events over a long period of time. That’s the unique part of this locality.”
I will continue to enjoy their adventures from the safety of my computer!
Jeff Martin: you were extraordinarily generous with your time and responses to my myriad questions. Likewise, I am in awe of how open you were with your experiences. For being willing to share all of this, I am truly grateful. It was an honor and a pleasure connecting with you!
When #CaveBison starts up again, you can be sure it will be on Twitter! Follow these scientists:
Jacquelyn Gill is one of three hosts of the podcast, Warm Regards, which discusses climate change.