The workers discovered the female cub while digging in the permafrost in the Klondike gold fields.
It is "the most complete mummified mammoth found in North America," according to the Yukon Territory government and the Tr'ondëk Hwëch'in indigenous people.
The elders of the Tr'ondëk Hwëch'in people gave him the name Nun cho ga (in English: big baby animal).
Geologists from the CA and the University of Calgary suspect Nun cho ga died during the Ice Age and was frozen in permafrost more than 30,000 years old.
Woolly mammoths inhabited Eurasia and later North America for hundreds of thousands of years.
The species became extinct on the mainland about 13,000 years ago – on some arctic islands several millennia later.
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Nun cho ga is "an incredible scientific discovery," said grant Zazula, a paleontologist from the agency responsible for broadcasting Global News.
Hair and skin were preserved.
"If you look at her feet, she has tiny little fingernails and toenails that have not yet fully hardened." She is about 140 centimeters long.
Initial investigations indicated that she was about a month old when she died.
It is only the second woolly mammoth cub to be discovered worldwide, the report said.
In 1948 parts of a mammoth calf, named Effie, were found in a gold mine in the US state of Alaska.