My Fun Evolution Trip Part Five: A Visit to a Prairie Dog Town

On the next day of the evolution trip (see previous entries below), my companions and I visited the Badlands, about fifty miles east of the Black Hills, in the driest part of the short grass prairie. We drove through Scenic, a nearly abandoned town where the now-closed bar catered to some Lakota men who had a lot of time on their hands. I remember these men from the 1990s, and they were nice and interesting people.

I have lots of bad things to say about soil erosion, but it can be starkly beautiful in the Badlands, where it occurs slowly enough that the plants and animals have been able to adjust to it.

The Badlands consists of mountains and cliffs of dirt, but it is dirt from the Cenozoic Era, sediments (sometimes with large mammal fossils) that never consolidated into rock. Some of the sediments were bright yellow and red, because they were deposited during a period of drier climate when the iron oxidized more.

The best part was when we drove a few miles out on a dirt road to the prairie dog town. Prairie dogs are not dogs; they are sort of like ground squirrels. Their most notable feature is their communal system of interconnected tunnels in which they live, relatively free from predators. There are a few predators, such as the black-footed ferret, which can slink down into the tunnels, grab sleeping prairie dogs, and chew them into a bloody mess. Do the prairie dogs have any defense against such predators?

Yes, and that defense is altruism, regarding which I have written many times and will write many more times. Some of the prairie dogs stand guard at tunnel entrances, and if a predator (or a human whom they think might be) approaches, they give a warning chirp and dive into the tunnel. In so doing, they put themselves at increased risk of getting caught by the predator. But even if the guard gets killed, his genes make it into the next generation because his relatives may reproduce more. That is, even a guard that gets killed may have enhanced inclusive fitness. In this case, the guards seemed more curious than alarmed and approached me, perhaps hoping for some food. This particular prairie dog town gets a constant stream of human visitors. Was it my imagination that they were trying to be cute? This is an evolutionary strategy that worked for cats.

Besides the evolutionary story of altruism, a prairie dog town is a good place to study the ecological effects of animals on their ecosystems. Without prairie dogs, the short grass prairie has a thick sod of grass stems and roots, into which a little seedling has little chance of growing. Most of the annual wildflowers (such as the scarlet globemallow, no longer in bloom when we visited) grow only in areas where the sod has been disturbed. This occurs where the prairie dogs dump their excavated soil (and fertilize it with droppings), and where the bison wallow. Bison do not have hands and cannot scratch parasites so they have to wallow around on the ground for relief. In the photo, note the prairie dog on the mound of disturbed soil with globemallows, and the bison in the distance.

The prairie dogs even have an effect on other animals. Burrowing owls do not dig their own burrows but nest in prairie dog tunnels.

The wind was extreme when we visited the prairie dog town, so the videos at that site were worthless. But two days later, at Devil’s Tower, my videographer Sonya Ross made an excellent recording which I will post in due time on YouTube.

Prairie dogs are not popular among ranchers, who like to poison them. The reason is that bison are smart enough to not step in the holes, but cows are stupid and step in the holes and break their legs. Prairie dogs are routinely poisoned on private land, and have occasionally been poisoned on federal land leased by ranchers from the government. Ranchers generally consider federal land to be theirs, rather than the property of all American citizens, and in some cases ranchers have protested for the right to graze their cattle on these lands for free. (They call this private enterprise rather than communism.) But at least, as far as I could see, the prairie dogs actually within the borders of Badlands National Park are safe.

As we left the park, we saw a herd of bighorn sheep, including a mother with a kid that was just learning how to jump around on the cliffs. With twenty cars and a dozen photographers around for this impromptu show, the sheep seem to have lost some of their fear of humans.

My Fun Evolution Trip Part Three: The Great Unconformity of the Black Hills

One of the greatest new insights into the history of the Earth was when James Hutton realized that the Earth had to be very old and that geological deposits were recycled over and over again—an idea called uniformitarianism. Hutton was not the first person to think of this but he was the first to pursue the idea in an organized fashion. His complex thoughts were later summarized by John Playfair and extended by Charles Lyell. As the modern paleontologist Michael Benton has explained, uniformitarianism can mean lots of things, some of which (such as uniformity of process) is still accepted by modern scientists, but others of which (such as uniformity of rate) are not. The former means that you can understand the past by studying the processes of the present, rather than invoking random miracles. The latter means that those processes have operated as slowly in the past as they are at present, which is clearly not the case.

Hutton, loving near Edinburgh, Scotland, in the late eighteenth century, looked at the local geological deposits and thought about them. At Siccar Point is an unconformity with nearly vertical Silurian sedimentary layers on the bottom and gently sloping Devonian and Carboniferous sedimentary layers on top, with millions of years of missing history in between. He realized that such sedimentary deposits could not have formed all at once during a global flood. And here’s why.

When the older, lower sedimentary layers formed, they had to be horizontal, due to the law of gravity. But these layers had been turned on their sides. If they were still mud when turned sideways, they would have gone PHHHHHHT! and squished into a big pile. The fact that they retained their layers meant that they had become rock before being turned on their sides. Then other sedimentary layers formed on top of them. This simply could not have happened during a single global Flood of Noah. Of course, creationists then as now could simply invoke miracles. They could say that God squished the lower layers into rock and turned them on their sides in the middle of the Flood. Does the Bible say this? No, they just make it up.

You can go to Scotland and see it for yourself. Sounds to me like a great excuse to go to Scotland. But there are other formations called The Great Unconformity, including the one John Wesley Powell discovered in the Grand Canyon. An unconformity is a geological formation in which a large chunk of time is missing. But there is a really good one (which didn’t make it into the Wikipedia entry) in the Black Hills of South Dakota, which has Precambrian sediments raised at a 70 degree angle on the bottom, and horizontal Cambrian strata on top, with almost two billion years of missing strata.

It is difficult to get directions to find it. So remember this. Find Nemo Road west of Rapid City. There are several ways to get there. Just as soon as this road, as you go west, crosses over the line from Pennington County into Meade County, you will see a bridge over Boxelder Creek. Immediately to your left is the Great Unconformity.

This is what it looks like from Nemo Road:

Even though it is in Black Hills National Forest, there are private landholdings all around, so you need to stay away from people’s yards. You will probably find, as I did, a path worn through the grass by generations of geology students from the South Dakota School of Mines and Wheaton College Science Station. There are other places to see the unconformity, but this is the only place where you can walk right up to it and put your finger on almost two billion years of missing history.

How could this unconformity have formed all at once during a flood? But maybe creationists have another explanation. Maybe the lower Precambrian layers were pre-Flood, which would have given ample time (almost two thousand years) to form the sediments into rock and then push them to their current 70 degree angle, and then the upper sediments were of Flood origin. This approach is not much help, however, because two thousand years is not enough time to have turned all the Precambrian sediments into rock and pushed them over, unless God did a miracle which the Bible conveniently does not mention.

So when you are in the Black Hills, forget about Deadwood and even Mt. Rushmore. The only really interesting thing, to me, about Mt. Rushmore, is the remnant populations of the rare fern Asplenium septentrionale that someone showed me in 1993 but which have apparently died. Go see the Great Unconformity, a hidden treasure—there is not even a road sign to mark the Nemo Road location.