Panda cub

SAN DIEGO --For weeks, San Diego Zoo staffers knew that Bai Yun, a 20-year-old female panda, might be pregnant. But given that she had had an unsuccessful pregnancy in 2011 -- and because only one other known panda has ever given birth at such an age -- they kept their enthusiasm in check.

But last Friday, based on several factors, including indications from a pair of high-tech tools used to monitor Bai Yun, they issued a birth watch, and today, Bai Yun delivered. No one knows yet the sex of the newborn cub, nor will they for weeks. But who cares? It's a newborn panda.

This is a picture of a previous panda cub at the zoo.