Over the weekend, the Smithsonian National Zoo welcomed its second litter of lions this year. Nine-year-old lioness Shera gave birth to four cubs on Sunday, after seven hours of labor. While the newest additions to the Zoo's Great Cats exhibit won't go on view to the public until the summer, they're visible on the Lion Cam. (You can look at the slightly older, but also pretty adorable litter of Shera's sister, Naba, here, too). Here's a video from the zoo showing the four cubs feeding and vocalizing: 

The zoo is "cautiously optimistic" that the four cubs will thrive, according to a statement released on Tuesday. For now, the zoo will let Shera tend to her cubs without intervention. Lions can take as long as six weeks to tend to their cubs in isolation before introducing them to the rest of a pride, and the National Zoo intends to mimic that process as closely as possible. The National Zoo's goal is to build a lion pride as part of their species conservation efforts. They're hoping to introduce the six new cubs total, along with the two mother lions and the father of both litters, to each other in the coming months. 

There's been something of a baby lion bonanza at the zoo this year:  Naba gave birth in late January — of her three cubs, two survived. Her litter was the first for the museum in four years.