SAN DIEGO -- It's springtime, and for San Diego Zoo panda resident Bai Yun, that means going through her annual mating ritual -- artificial insemination.

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The zoo announced Wednesday that its Giant Panda Conservation Team completed two procedures this week to artificially inseminate Bai Yun with semen from Shi Shi, her perpetually uninterested male counterpart.

Panda experts decided this was the best week because of her estrus level, said Barbara Durrant, a reproductive physiologist who performed the procedure.

"Combining her behavioral changes with Shi Shi's lack of interest in natural mating led us to conduct the operation at an optimal time with the help of our veterinarians, anesthesiologist and keepers," Durant said.

It will be months before keepers know if the panda is pregnant.

In 1999, Bai Yun gave birth to Hua Mei, the product of artificial insemination.

Last year's artificial insemination attempt was unsuccessful. This marks the fifth time Bai Yun has been inseminated since she and Shi Shi arrived in 1996 on an 11-year loan from China.

Because of Shi Shi's advanced age, keepers used frozen semen previously collected from him for the first time this year.

Bai Yun and Shi Shi will be off exhibit until further notice. Hua Mei can be seen in an alternative exhibit next to the regular giant panda enclosure, from 9:30 a.m. to 3:30 p.m.