Sierra Nevada red fox, one of North America's rarest, seen at Yosemite

LOS ANGELES (Reuters) - Biologists have spotted a Sierra Nevada red fox at Yosemite National Park in California for the first time - a sighting of one of the rarest mammals in North America, thought to number only 50 on the continent, officials said on Thursday.

Wildlife biologists who went on a backcountry trip to the far northern part of the park documented sightings of the endangered animal on Dec. 13 and Jan. 4, the National Park Service said in a statement.

"Confirmation of the Sierra Nevada red fox in Yosemite National Park's vast alpine wilderness provides an opportunity to join research partners in helping to protect this imperiled animal," Sarah Stock, a biologist at the park, said in a statement.

Yosemite National Park covers 747,956 acres (302,687 hectares) in eastern California. The nearest sightings of the red fox species have been in the Sonora Pass area north of the park, where biologists have monitored a small group of the animals since 2010, officials said.

Before that, the last sighting of the animal in the region was about 20 years ago.

Biologists will use remote cameras to continue to look for more Sierra Nevada red foxes in the park, officials said.

(Reporting by Alex Dobuzinskis in Los Angeles; Editing by Cynthia Johnston and Bill Trott)