The Mammoth Site, in the beautiful town of Hot Springs, South Dakota, is a truly unique place. What makes it so special is not the types of bones found here - mammoth skeletons have been unearthed throughout the Northern Hemisphere - but the sheer number of them. Over 60 mammoths have been found in an area that is only 36,000 square feet (that's a little more than half the size of a football field), and there are probably still more hidden below waiting to be uncovered.
The bones in the site date to approximately 26,000 years ago, and were only uncovered in 1974. In that year, a construction company was commissioned to work on a new housing development on the southern edge of Hot Springs. As they were digging on a particular hill, they began to find some odd bones, which were soon identified as belonging to a mammoth. The land owner, thankfully, agreed to allow scientists to investigate the area, and more and more bones were discovered. Once the significance of the site was realized, it was saved from becoming a housing development and was turned into a museum, and excavation continues today. Over 60 mammoths have been found so far, as well as a few other animals like prehistoric camels, bears, wolves, llamas, and rodents.
The bones in the site date to approximately 26,000 years ago, and were only uncovered in 1974. In that year, a construction company was commissioned to work on a new housing development on the southern edge of Hot Springs. As they were digging on a particular hill, they began to find some odd bones, which were soon identified as belonging to a mammoth. The land owner, thankfully, agreed to allow scientists to investigate the area, and more and more bones were discovered. Once the significance of the site was realized, it was saved from becoming a housing development and was turned into a museum, and excavation continues today. Over 60 mammoths have been found so far, as well as a few other animals like prehistoric camels, bears, wolves, llamas, and rodents.
Guided tours lasting about 30 minutes are available throughout the day, and are included in your admission price. Your tour guide will take you around the network of catwalks that surround the excavation sites and point out the notable finds. After your tour you are free to spend as much time as you like roaming around the site and to check out the small museum in the adjacent room.
Even when you first walk in, you can see an impressive amount of bones. It's a big site! Some bones have been removed for study, but many others have been left where they were found so visitors can see them in their original positions and locations. The portions of the rock that have been left intact are covered with a prolific layer of bones, which really helps you appreciate the amount of mammoth skeletons that have been found here.
Even when you first walk in, you can see an impressive amount of bones. It's a big site! Some bones have been removed for study, but many others have been left where they were found so visitors can see them in their original positions and locations. The portions of the rock that have been left intact are covered with a prolific layer of bones, which really helps you appreciate the amount of mammoth skeletons that have been found here.
But how did so many mammoths get preserved in one place?
I'm glad you asked. Several geologic and environmental factors all came together to create the Mammoth Site, but it all started with a cave far below the earth's surface. The cave eventually collapsed from the weight of the overlying rock, creating a sinkhole. Soon, a spring formed below the sinkhole and warm, mineral-rich water bubbled up to the surface, creating a small pond. This pond appeared attractive to the diverse wildlife that roamed the surrounding plains, but it held a hidden danger. The surrounding rock was composed of shale, and the walls encircling the pond were rather steep and slippery. If the water level in the pond was low, a mammoth would have to lean pretty far down to be able to reach it. And if that mammoth slipped and fell in to the pond? Bad news. The walls of the pond are already very smooth and steep, and mammoths, like their modern elephant relatives, have flat feet that are not at all suited for climbing. So any mammoth (or other animal) that fell in would never come back out - they would die of exhaustion or starvation in the pond. The pond existed over a period of time that lasted between 350 and 700 years, and many mammoths would fall to the same trap over that time. Their dead bodies sunk to the bottom of the pond, where they were gradually covered with sediment and buried. Eventually, however, the spring dried up and the muddy lakebed could trap only footprints. The sediments were cemented with calcite and turned to rock. This rock was more resistant to weathering than the surrounding shale, so as the shale eroded away, the former pond bed became a hill.
I'm glad you asked. Several geologic and environmental factors all came together to create the Mammoth Site, but it all started with a cave far below the earth's surface. The cave eventually collapsed from the weight of the overlying rock, creating a sinkhole. Soon, a spring formed below the sinkhole and warm, mineral-rich water bubbled up to the surface, creating a small pond. This pond appeared attractive to the diverse wildlife that roamed the surrounding plains, but it held a hidden danger. The surrounding rock was composed of shale, and the walls encircling the pond were rather steep and slippery. If the water level in the pond was low, a mammoth would have to lean pretty far down to be able to reach it. And if that mammoth slipped and fell in to the pond? Bad news. The walls of the pond are already very smooth and steep, and mammoths, like their modern elephant relatives, have flat feet that are not at all suited for climbing. So any mammoth (or other animal) that fell in would never come back out - they would die of exhaustion or starvation in the pond. The pond existed over a period of time that lasted between 350 and 700 years, and many mammoths would fall to the same trap over that time. Their dead bodies sunk to the bottom of the pond, where they were gradually covered with sediment and buried. Eventually, however, the spring dried up and the muddy lakebed could trap only footprints. The sediments were cemented with calcite and turned to rock. This rock was more resistant to weathering than the surrounding shale, so as the shale eroded away, the former pond bed became a hill.
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For anyone who doubts that mammoths would be clumsy enough to fall into a watery deathtrap like this, I present to you Exhibit A:
 An elephant I saw on my recent trip to Africa on the edge of a river, stopping to drink and splash some water on his back. |  That same elephant moments later, totally faceplanting into the embankment. |
Another interesting tidbit about the mammoths that have been found in the Site: every last one of them is male (as is the elephant in the above photos, by the way). And they're all relatively young. There's a simple ecological reason for this. Mammoths, like elephants, live in matrilineal social groups, meaning that females stay with the herd they're born into for their entire life. This provides some protection for young adolescent females because there are older and wiser elephants around to serve as role models and to prevent them from doing anything foolish. Male elephants and mammoths, however, leave their birth herd once they reach sexual maturity and spend much of their adult lives alone, only joining up with female-led herds for short periods of time to mate. A lone adolescent male doesn't have any older adults around to steer him away from dangerous watery deathtraps, so they are more likely to attempt to get water out of one, and thus more likely to accidentally become trapped.
The moral of the story? Boys are dumb.
Anyway, getting back to the tour, this is the bone that lets researchers know the sex of a mammoth from its skeleton - the pelvic bone. Females have a much wider space in the pelvic bone than males do, because females need to have enough room for a baby to pass through that opening and males, obviously, do not. So you can determine a skeleton's sex by taking measurements of its pelvis.
The moral of the story? Boys are dumb.
Anyway, getting back to the tour, this is the bone that lets researchers know the sex of a mammoth from its skeleton - the pelvic bone. Females have a much wider space in the pelvic bone than males do, because females need to have enough room for a baby to pass through that opening and males, obviously, do not. So you can determine a skeleton's sex by taking measurements of its pelvis.
The long curved tusks are the most recognizable bones, but you can also see leg bones, ribs, and even teeth, which have a distinctive ridged appearance similar to modern elephant teeth.
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 lower jaw with teeth |  underside of a skull with teeth |
Much of the site looks like a random jumble of bones, but there are a few skeletons that have been preserved relatively intact and with their bones still more or less in their correct arrangement. The top right photo above is one (its back end is closer to us - you can see the pelvic bone and femurs below the ribcage), as is this one, which comes with a nice diagram to help you understand what you're looking at.
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In addition to bones, there are also many footprints preserved as trace fossils. After the spring dried up and the lake filled with sediment, this became a safe, muddy place that many animals traveled across. Many footprints can be seen throughout the site, marked for easy identification with arrows or circles. This is one of the clearest sets of mammoth footprints. On the left one, you can clearly see the blunt, cylindrical shape of a mammoth's foot that sunk down into the muddy lakebed.
This is still a working archaeological site, and you can peek in on an area that is currently under excavation. You can see tools and buckets full of rock awaiting analysis. If you come during working hours, you may even be lucky enough to see archaeologists digging!
The exit to the site takes you into a small museum where you can see many of the bones that have been discovered in the site. In the center of the museum is a mammoth skeleton, as well as a recreation of what the mammoth would have looked like with flesh and skin. They also have a skeleton of a giant short-faced bear, an extinct species of bear whose skeleton was trapped in the mammoth site.
If you take the elevator down from the museum, you can actually visit the lab where people are busy at work analyzing the bones that have been found at the site. A row of windows lets you peek in and see what the scientists are doing. I was there late in the day, so there was only one person there, who was operating some kind of loud machinery that (I think) was cleaning bits of rock off the bones. There are work stations right on the other side of the windows, and some of the other workers had posted notes on the windows to let visitors know what they were doing. One note beside a large tray of small rocks and a high-powered magnifying lens said that the worker here had been picking through the debris looking for bone fragments from mice, rabbits, and other small mammals. Sounds like quite a job!
If you take the elevator down from the museum, you can actually visit the lab where people are busy at work analyzing the bones that have been found at the site. A row of windows lets you peek in and see what the scientists are doing. I was there late in the day, so there was only one person there, who was operating some kind of loud machinery that (I think) was cleaning bits of rock off the bones. There are work stations right on the other side of the windows, and some of the other workers had posted notes on the windows to let visitors know what they were doing. One note beside a large tray of small rocks and a high-powered magnifying lens said that the worker here had been picking through the debris looking for bone fragments from mice, rabbits, and other small mammals. Sounds like quite a job!
 giant short-faced bear |  the lab, with specimens awaiting analysis |
All in all, it was a really neat place to visit. I mean how often do you get to tour a real working archaeological site? Especially one as unique as this one, with so many visible fossils. It's a fascinating addition to any Black Hills trip.
The Mammoth Site
The Mammoth Site is in the town of Hot Springs, South Dakota, which is actually a pretty cool town. Check out my post on it here.
The Mammoth Site is in the town of Hot Springs, South Dakota, which is actually a pretty cool town. Check out my post on it here.
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