Smithsonian.com

Pregnancy watch begins today. Is Mei Xiang, the Zoo's female panda pregnant? Photograph by Mehgan Murphy

Springtime and our thoughts turn to progesterone. As every panda watcher knows, this is the time of year when we all wait with bated breath to see if the Zoo’s female giant panda is pregnant. And the only way to know for certain that she is, would be the birth of panda cub 40 to 50 days from now.

Today, the Zoo announced that researchers detected “a secondary rise in urinary progestagen levels” in Mei Xiang and what that means is, well maybe she’s preggers. The problem is that giant pandas have a high chance of pseudopregancies.

“The hormonal dynamics of pregnant and pseudopregnant pandas are extremely similar,” said reproductive biologist Janine Brown in a statement. “So we remain hopeful, but cautious.”

The 11-year-old Mei Xiang went into heat in early January and spent some time with her 12-year-old mate Tian Tian, but researchers decided to artificially inseminate the female panda as an extra precaution. The Zoo is checking Mei Xiang’s hormone levels weekly and conducting other tests.

This is the eighth year that the Zoo has tried to breed the pandas. Its single success in 2005 resulted in the much heralded birth of Tai Shan, who was returned to China earlier this year. Both Mei Xiang and Tian Tian are on loan from the Chinese government through the end of 2010.