Fighting panda extinction

What's odd about a panda getting pregnant? Nothing, really. It's apparently not a commonplace thing in captivity, but it's not really strange that a panda female gets impregnated.

The strange part is that the creature warrants a "24-hour birth watch".

SAN DIEGO - A giant panda at the San Diego Zoo is pregnant again and expecting her fourth cub sometime in August.

The zoo said Tuesday that 16-year-old Bai Yun was put on "24-hour birth watch" after officials detected a fetus and fetal heartbeat through ultrasound images July 18. Additional tests confirmed the pregnancy was going normally. [emphasis added]

Then why the need to watch her 24 hours a day?