Resilience.

In the mid-1800s, a railroad director, entrepreneur, and politician named Lewis Henry Morgan began visiting a largely undeveloped swath of land dotted with beaver ponds in Michigan’s Upper Peninsula. What he saw amazed him: “[A] beaver district, more remarkable, perhaps, than any other of equal extent to be found in any part of North America,” he wrote. “A rare opportunity was thus offered to examine the works of the beaver, and to see him in his native wilds.”

Morgan wasn’t your typical nature buff. His pioneering anthropological studies of Native American tribes had already begun to make him an enormously influential figure in 19th century science. In 1880, he would be elected president of AAAS (publisher of Science), and Charles Darwin, Sigmund Freud, and Karl Marx would come to cite his work. But as Morgan helped his railroad company lay tracks across the Michigan wilderness in the 1850s and 1860s, the target of his scientific curiosity was the North American beaver (Castor canadensis).

For years, he carefully documented how the beavers behaved and where they built their dams and ponds. Then, in 1868, Morgan published his 396-page beaver bible: The American Beaver and His Works. Folded into each copy was a map, carefully drawn by his railroad’s engineers, which detailed the locations of 64 beaver dams and ponds spread over some 125 square kilometers near the community of Ishpeming.

Now, that rare map is giving researchers some new insight into just how busy beavers can be. A new survey shows that many of the dams and ponds that Morgan saw nearly 150 years ago are still there—testament to the resilience of the rodents and their ability to maintain structures over many generations.

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