In the wild, giant panda mating occurs just as nature specials would have you believe. There’s intense competition for each female, and the dominant male will mate with her several times to ensure success. And that strategy works: Wild female pandas generally give birth every two years. But that low birth rate means that captive breeding programs are essential to sustaining the endangered species. And in captivity, mating and successful pregnancies are tricky affairs—which is why it’s always a big deal when a cub is born, and devastating when one dies, as the 6-day-old cub at the National Zoo did last week.