Volunteers at the National Zoo are preparing to begin a 24-hour pregnancy watch to see if the female giant panda gives birth to a cub this weekend.
Beginning at 4 p.m. Friday, about 40 volunteers will rotate shifts, logging Mei Xiang's behavior. The zoo says they have already observed her spending more time shredding bamboo in her den to make a nest.
Zoo scientists have determined Mei Xiang's hormone levels are nearing baseline, which indicates the end of either a real or pseudo pregnancy. She was artificially inseminated in January.
Pandas' hormone levels and behavior can indicate they are pregnant when they're not.
Mei Xiang gave birth to her only cub, Tai Shan, in 2005. He was sent to a breeding program in China earlier this year.
On the Internet: