Zookeepers at the National Zoo examine a newborn panda while its mother, Mei Xiang, was out of her den on Sept. 5. (Smithsonian’s National Zoo)

Local philanthropist David M. Rubenstein is donating another $4.5 million to the National Zoo’s giant panda research and conservation program, the zoo announced Thursday.

The Washington zoo, where twin panda cubs were born last month, said the money will fund, through 2020, research into panda reproduction, training programs, upgrades to the giant panda habitat and care for the pandas living there.

The zoo is home to an adult female giant panda, Mei Xiang, and adult male, Tian Tian, a female 2-year-old, Bao Bao, and an unnamed 4-week-old male cub, born Aug. 22. A second male born the same day died Aug. 26.

Rubenstein, a founder of the Carlyle Group, a Washington-based global private-equity firm, has now donated $9 million to the giant panda program since 2011, the zoo said in a statement.

He announced an initial $4.5 million panda donation in December 2011.

Rubenstein has been a member of the Smithsonian’s Board of Regents since 2009.

“The National Zoo’s panda program has been a remarkable success — two healthy pandas in just two years — and I am pleased to support it for another five years,” Rubenstein said, according to the zoo.

Dennis Kelly, the zoo’s director, said in the statement that Rubenstein’s generosity “allows us to focus on one critically endangered species, but in doing so, we leverage all we learn to better manage other species in human care and in the wild.”

Giant pandas are native to China, and the Chinese own and lease all giant pandas held at U.S. zoos.

The zoo is nearing the end of a five-year agreement whereby it pays China $500,000 a year to lease its pandas, and requires all cubs born at the zoo to go to China when they turn 4.

Officials are negotiating a new lease. The current agreement expires Dec. 6.