A Washington state zoo said an endangered red wolf gave birth to at least six pups on Mother's Day as part of a nearly 40-year-old breeding program.

The Point Defiance Zoo & Aquarium in Tacoma said 8-year-old Millie went into labor about 10 p.m. Sunday at the Red Wolf Woods exhibit and gave birth to two pups with an additional four pups being born early Monday, The (Tacoma) News Tribune reported Wednesday.

Zoo staffers said each of the cubs, which were fathered by 9-year-old red wolf Graham, weighed about 13 ounces at birth.

Will Waddell, the zoo's red wolf program coordinator, said the cubs were conceived as part of a breeding program designed to protect the species from extinction.

"It gives us an opportunity to highlight the program and let the folks who visit the zoo, and the community, know about our involvement in the program and some of the challenges that red wolves still face," Waddell said.

Officials said the pups will remain with their parents for at least a year until biologists decide whether to send them to other zoos as part of the breeding program. (c) UPI