Ying Ying and Le Le, both 14 years old, had attempted to mate since 2010 but never managed to successfully do so, according to a press release from Ocean Park.
Yet in late March, Ying Ying, the female, began to show signs that her hormonal levels were changing and Le Le, the male, left scent-markings around his habitat while searching for Ying Ying's scent. The zoo noted this is common behavior during breeding season, which occurs between March and May.
On Monday at 9 a.m. local time, the two pandas successfully mated, the zoo said.
The park had been closed since January due to the coronavirus spread, which has infected more than 1.3 million people globally.
"The successful natural mating process today is extremely exciting for all of us, as the chance of pregnancy via natural mating is higher than by artificial insemination,” Michael Boos, executive director in zoological operations and Conservation at Ocean Park, said in a statement.
It is still too early to tell whether Ying Ying is pregnant. The gestation period for giant pandas ranges between 72 and 324 days. The earliest a pregnancy can be detected is 14 to 17 days before birth.
"We hope to bear wonderful pregnancy news to Hong Kongers this year and make further contributions to the conservation of this vulnerable species," Boos said.