The National Zoo in Washington announced Monday it had received a $4.5 million donation from a rich US benefactor which will fund a five-year study into preservation of the giant panda. The money from David Rubenstein, co-founder of the Carlyle Group, a global investment house, will fund conservation and reproduction programs in China, scholarships and training, and refurbishment of panda enclosures in Washington. \"We are honored to be part of a cherished program that brings joy to millions of people and draws together two great nations working to preserve these magnificent and gentle giant pandas,\" said Rubenstein. The Smithsonian has a partnership with the China Wildlife Conservation Association. The Washington zoo, run by the Smithsonian Institution, is home to two giant pandas, Tian Tian, a male, and Mei Xiang, a female, who had a cub -- Tai Shan -- in 2005 through artificial insemination. The National Zoo is to receive frozen semen from San Diego\'s now deceased panda, Shi Shi, later this year, to be used if its own pandas do not again mate successfully. Giant pandas kept in captivity are known for their low sex drive, further exacerbating an already threatened species. There are only an estimated 1,600 pandas in their natural habitat, mostly in China, and around 300 more in captivity, according to the World Wildlife Fund. Rubenstein, has been a member of the Smithsonian board since 2009. \"His generosity will enable us and our Chinese partners to continue our conservation work to give this critically endangered species the chance to survive in its native habitat,\" the zoo said in a statement.