Caitlin Burrell, research scientist at the Smithsonian Conservation Biology Institute, returned from China last night April 20, with frozen giant panda semen that had been stored at the Bifengxia Giant Panda Base's cryopreservation bank. The sperm may be used for an artificial insemination on the Zoo's female giant panda Mei Xiang (may-SHONG) when she goes into estrus this spring. This is the first time frozen semen has been transported from China to the National Zoo for breeding.
The semen sample was collected from Hui Hui (h-WEI h-WEI). A cub sired by Hui Hui would be more genetically valuable than a cub sired by the National Zoo's male Tian Tian (t-YEN t-YEN). Hui Hui lives at the China Research and Conservation Center for the Giant Panda in Wolong, Sichuan Province. He is 9 years old and has not yet sired any cubs.
The frozen semen was flown from Chengdu and kept frozen at minus 196 degrees Celsius in liquid nitrogen for the more than 7,000-mile journey. After landing at Dulles International Airport, the semen was taken to the SCBI's cryopreservation bank at the National Zoo. The Zoo documented the trip on its @SmithsonianZoo Instagram account using #InstaScience and #PandaStory.
“This is the first time we have imported semen from China for panda breeding,” said Dennis Kelly, director of the Smithsonian's National Zoo. “I want to thank everyone involved, including the U.S. Fish and Wildlife Service, China's State Forestry Administration, and our own team of panda scientists, who made this transport possible.”
The National Zoo received the semen as the result of a breeding recommendation. Each year SCBI scientist Jon Ballou calculates the best genetic matches for all of the eligible breeding pandas around the world. He originally developed the mathematical formula used to make the recommendations in the 1990s for golden lion tamarins. It is now used to make breeding recommendations for all species managed by Species Survival Plans in human care. Scientists are working to preserve 90 percent of the genetic diversity of the giant pandas living in human care for the next 200 years. There are currently 392 giant pandas living in human care; scientists hope to grow the population to 500 bears.
The Zoo's panda team expects that Mei Xiang will go into estrus for 24 to 72 hours this spring. Research shows that females usually go into estrus 45 to 50 days after they have weaned and separated from their cubs. The panda team slowly simulated that natural process for Mei Xiang and 20-month-old juvenile Bao Bao. They have been living separately since March 1.
Mei Xiang and Tian Tian have produced two surviving cubs while living at the National Zoo. Tai Shan, their first cub, was born July 9, 2005. He now lives in China. Bao Bao, their second cub, was born Aug. 23, 2013. She will leave the Zoo and travel to China when she turns 4 years old.
China's State Forestry Administration released new giant panda census data in February; an estimated 1,864 giant pandas are now living in the wild. That is an increase of 16.8 percent since the last census, which found 1,600 pandas in the wild.