Pack-rat nest
As you cross any of the level, well-grassed prairie regions in the Yellowstone you will see piles of soft earth thrown up in little hillocks, sometimes a score or more of them bunched together. The drivers will tell you that these are molehills, which isn't quite true. For the Mole is a creature unknown in the Park, and the animal that makes these mounds is exceedingly abundant. It is the common Mole-gopher, a gopher related very distantly to the Prairie-dog and Mountain Whistler, but living the underground life of a Mole, though not even in the same order as that interesting miner, for the Mole-gopher is a rodent (Order Rodentia) and the Mole a bug-eater (Order Insectivora); just as different as Lion and Caribou.
The Mole-gopher is about the size of a rat, but has a short tail and relatively immense forepaws and claws. It is indeed wonderfully developed as a digger.
Examine the mound of earth thrown up. If it is a fair example, it will make fully half a bushel. Next count the mounds that are within a radius of fifty paces; probably all are the work of this Gopher, or rather this pair, for they believe in team play.
Search over the ground carefully, and you will discern that there are scores of ancient mounds flattened by the weather, and traces of hundreds, perhaps, that date from remote years.
Now multiply the size of one mound by the number of mounds, and you will have some idea of the work done by this pair. Finally, remembering that there may be a pair of Gophers for every acre in the Park, estimate the tons of earth moved by one pair and multiply it by the acres in the Park, and you will get an idea of the work done by those energetic rodents as a body, and you will realize how well he has won his Indian name, the "Upheaver."
We are accustomed to talk of upheaval in geology as a frightful upset of all nature, but here before our eyes is going on an upheaval of enormous extent and importance, but so gently and pleasantly done that we enjoy every phase of the process.
The Mole-gopher