JOHNSON CITY, Tenn. (WJHL) — New research completed by East Tennessee State University (ETSU) alumni suggests beavers have been changing the forests and rivers of North America for the last seven million years, the university announced on Monday.

According to ETSU, the research comes from a study published in the journal “Palaeontologia Electronica” by Kelly Lubbers, bonebed paleontologist at The Mammoth Site in South Dakota and an alumnus of ETSU’s paleontology master’s program, and Dr. Joshua Samuels, associate professor in the ETSU Department of Geosciences and curator at the Gray Fossil Site & Museum.

The modern beaver in North America belongs to the Castor canadensis species and is often compared to the extinct Castor californicus species.

The two species are very similar and some researchers have questioned whether they are truly distinct species, ETSU stated in a release. The main factor that distinguishes the two is their size as the extinct C. californicus species was reportedly larger.

“Size alone is not a good metric for distinguishing species,” said Lubbers. “We wanted to take a closer look and see if we could find any other similarities or differences that might tell us if they really should be considered different species.”

The team of researchers conducted measurements on over 120 beaver specimens from across North America. Results found only minor differences between the modern and extinct species, including overlap in body size, the release said.

The similarities indicate that the extinct beavers had a similar lifestyle to their modern relatives, suggesting that environments in North America have been shaped by beaver activity for seven million years, ETSU said.

“Based on our findings, I am quite confident that Castor californicus would have had a lifestyle and ecology indistinguishable from living beavers,” said Samuels.

Researchers said that more work will be needed to determine whether modern beavers represent the same species, including further study on particular parts of the beavers’ bodies.

“Castor californicus was initially described as a separate species based on its teeth,” said Lubbers. “I think by comparing the teeth of fossil and extant beavers, this will give us a better indication as to whether they really are separate species or not.”

To learn more about ETSU’s Department of Geosciences, click here.