Ancient beavers leave traces of dam in Yukon

Paleontolgists unearth what they believe is a 125,000-year-old beaver dam in Old Crow, Yukon.

Scientists in the Yukon have uncovered the remains of what they believe is a 125,000-year-old beaver dam.

The dam was unearthed during a paleontological survey in the Old Crow basin, about 1,000 kilometres north of Whitehorse. Scientists were conducting a survey of ancient mammal fossils along the Porcupine and Old Crow Rivers when they made the find.

The fossilized artifact is the first intact fossil beaver dam to be reported, according to paleontologists from the Government of Yukon and the Canadian Museum of Nature.

At a separate site on the Porcupine River downstream from Old Crow, the team also unearthed additional beaver-cut sticks in sediment, which might date back as far as three to five million years. It is possible that this particular find represents the oldest beaver-cut wood in the world.

Paul Matheus, a Yukon government paleontologist, says the age will be better known once volcanic ash at the site is dated. He says the sticks could be as old as or older than a four-million-year-old beaver site discovered in 2003 on Ellesmere Island.

It appears beavers gnawed down the trees. Matheus couldn't say if the fossilized dam was built by the now-extinct giant beavers that roamed the region, known as Beringia, 90,000 years ago. Paleontologists are studying the wood to make that determination.

"Giant beavers were not ancestors of modern beavers," says Matheus.

"It is still uncertain to what extent they actually cut and processed wood. The best leads for future research into this question lie in the Yukon's fossil record, particularly the Old Crow region."

Both sites will be busy locations in the future. More collection expeditions, educational programs for students, and public presentations by paleontologists and other scientists are planned.