Mei Xiang, the female at the US National Zoo on loan from China, is not pregnant after all despite efforts to breed another giant panda cub.
She had been artificially inseminated in early April but zoo scientists said they have not seen a fœtus during ultrasound exams as a hormone associated with pregnancy began to decline in recent days.
Mei experienced hormonal changes and behaviors like those of a true pregnancy, as she has done three times previously.
In 2005, she gave birth to one cub, Tai Shan (left).
The black-and-white giant panda is one of the world's best-known endangered species and breeding is difficult.
Giant pandas typically ovulate once a year and the zoo said it would consider next year whether to try again.
As part of the original ten year deal to bring Mei Xiang and male panda Tian Tian to the United States, any offspring were to be returned to China after the cub's second birthday.
However, in April Beijing agreed to allow the cub to stay for another two years.
