WASHINGTON - The National Zoo is anxiously awaiting the potential arrival of a new panda cub. The tricky part is determining whether or not giant panda Mei Xiang is actually pregnant.
Scientists say they have detected a rise in urinary progesterone, which means either she will give birth or experience the end of a pseudopregnancy in 40 to 50 days.
The giant panda has had five pseudopregnancies since 2007. Mei Xiang birthed her only cub, Tai Shan, in 2005.
Fake pregnancies identically mimic real pregnancies, minus the fetus. Female pandas sleep more than normal, make nests and experience high hormone levels, according to Live Science. Panda fetuses do not develop until the final weeks of gestation, making most of the pregnancy a guessing game.
Track Mei Xiang's progress live on the National Zoo's panda cam.
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