The Smithsonian National Zoo posted a video of four lion cubs born Sunday at the zoo to 9-year-old Shera. (Video courtesy Smithsonian National Zoo)

The four lion cubs born last weekend at the Smithsonian’s National Zoo are doing well and are expected to make their debut in June.

The cubs were born Sunday to Shera, a 9-year-old African lion. The delivery took nearly seven hours, zoo officials said.

The father is Luke, who also has been named as the father of two female cubs born at the zoo Jan. 24, to a second lion, Nababiep. The four cubs are Shera’s second litter — and the fifth for 8-year-old Luke.

Zoo staff watched Shera give birth via a closed-circuit webcam. The first cub was born at 8:27 a.m. and appeared “active and healthy,” zoo officials said. The other cubs were born at 9:03 a.m., 11:09 a.m. and 3:17 p.m.

Craig Saffoe, curator of the Great Cats exhibit at the zoo said Wednesday that the cubs “look great” and that from the cameras it looks like “everybody’s nursed.” He said Shera was “denned up” with her cubs and as “secluded as possible.”

Zoo officials do not yet know the sex or weight of the cubs because they’re being left alone with their mother.

“Like any mom, she needs some peace and quiet to bond with her cubs, so we’re giving her the solitude she needs,” said Kristen Clark, an animal keeper at the Great Cats exhibit.

“From what we’ve observed,” she said, “her behaviors are right on point and there’s no need for us to intervene.”

Shera raised her previous four cubs with success, so zoo officials are “cautiously optimistic that these cubs will thrive,” Clark said.

The average gestation period for a lion is 110 days. Shera gave birth at 114 days, Saffoe said.

The zoo said both mothers have space apart from each other and from Luke, but introductions will be made at the appropriate time.

“Our aim is to bring all nine lions together,” said animal keeper Rebecca Stites.

In the wild, a lion can take up to six weeks to introduce her cubs to the rest of her pride, so zoo officials said they are following the same schedule. The zoo’s animal keepers and veterinary team will continue to watch and eventually examine the cubs. The latest batch of cubs will go on public exhibit in June, and the two that were born in January will go on exhibit in May.

The newest lion cubs can be seen via a live camera on the zoo’s Web site. Two 7-month-old Sumatran tigers — Bandar and Sukacita — are on exhibit at the zoo.

The birth of the lion cubs is part of the zoo’s effort to build its lion population. The zoo is part of the African Lion Species Survival Plan being run by the Association of Zoos and Aquariums. The plan matches animals across the country for breeding.

Saffoe said lions are a “bit more predictable” than most other cats when it comes to breeding because the females “let the males known exactly what they want.”

“Imagine a 300-pound cat who would normally hiss and spit at anything that comes near her, and then she starts rubbing her head on everything she can get,” he said. “She starts rolling over side to side. She will present herself to the male.”

Zoo officials said the number of African lions in the wild has fallen by 30 percent over the past 20 years as a result of disease, habitat loss and poaching. The International Union for Conservation of Nature classifies the African lion as vulnerable.