At 2 weeks old, the Smithsonian’s National Zoo’s three African lion (Panthera leo) cubs born to 6-year-old Nababiep Sept. 22 appear to be healthy, Zoo veterinarians said today after completing the cubs’ first health exam.

“We’re happy to see that the cubs are growing and that each appears to be in good health,” said Dr. Jessica Siegal-Willott, supervisory veterinarian at the Zoo. “Naba has done a great job nursing them and we’ll continue to monitor their development.”

The veterinary team checked the cubs’ mouths and eyes, listened to their hearts and lungs and felt their bellies, but the animals are still too young to receive vaccines. The cubs weigh between 7 and 8 pounds.

Because the cubs are just 2 weeks old, animal care staff continues to be cautiously optimistic. The mortality rate for cubs younger than 1 year old in human care in 2009 was about 30 percent, compared to a 67 percent mortality rate for cubs in the wild. The cubs’ next exam will be in about a month.

On Sept. 17, the Zoo’s four other lion cubs, born to Naba’s sister, Shera, Aug. 31, underwent their first health exam and all four also appeared to be healthy.

Although it is difficult to determine the sex at such a young age when genitalia have not fully developed, at this time two of the cubs appear to be male and one appears to be female. Only when a male’s scrotum begins to develop or the prepuce (the skin around the penis) becomes prominent can the animal care team say what the animal’s sex is with certainty.

In fact, at the end of last week, the Zoo’s animal care team identified that there was a prominent prepuce and scrotum on one of Shera’s four cubs and determined that one to be male—so rather than four females, Shera has three females and one male cub. The animal care team will confirm the sex of Naba’s three cubs at the next exam.

Luke, the Zoo’s 5-year-old male lion, is father to all seven cubs and is the most genetically valuable lion in the Association of Zoos and Aquariums’ Species Survival Plan for African lions. An SSP matches individual animals across the country for breeding in order to maintain a healthy, genetically diverse and self-sustaining population.

“We’re thrilled to have seven genetically valuable cubs that will grow up and go on to contribute to the continued genetic health of the Association of Zoos and Aquariums’ lion Species Survival Plan,” said Craig Saffoe, interim curator of the Zoo’s Great Cats Exhibit.