VICTORIA - Indigenous groups on both sides of the Canadian and U.S. border are working with the British Columbia government and others to save a critically endangered species of woodland caribou.

The Kalispel Tribe in Washington state is among those leading a project building a caribou maternal pen on land owned by the Nature Conservancy of Canada in the mountains of B.C.'s West Kootenay.

Tribe spokesman Mike Lithgow says the eight-hectare pen is being built where it's expected about six south Selkirk mountain caribou will give birth later this year.

The pen is 4.57 metres high, has electric fencing on its exterior and is covered with a fabric that acts as a visual barrier for predators.

Lithgow says the cows will be caught using a net gun from a helicopter and then relocated to the pen to protect them from predators that have killed as many as three-quarters of the offspring in the past.

The tiny herd of caribou, listed as among the most endangered mammals in North America, primarily roam high-mountain, old-growth forests in northeastern Washington state and northern Idaho.