Giant pandas Le Le and Ying Ying rest beside their "birthday cake" made from ice and fruits at Hong Kong Ocean Park.

Hong Kong's pandas Le Le and Ying Ying have been given some privacy away from the prying eyes of tourists this week in a bid to encourage them to mate, their handlers said on Tuesday.

Ocean Park aquarium and animal theme park closed its panda exhibit for three days from Monday after Ying Ying started showing signs that she was ready for love, spokeswoman Una Lau said.

“They live separately but during this mating season we put them together and hopefully they will mate,” she said.

Female pandas are only interested in mating for three days a year, so park managers were quick to react when Ying Ying started displaying tell-tale signs such as increased water play, bleating and restlessness.

Lau said the six-year-old pandas from China's Sichuan province were “very interested” in each other. They became sexually mature only last year.

There are fewer than 1 600 pandas left in the wild, according to WWF conservation group.

Females can only become pregnant during a 12 to 24 hour period once a year, and the males' proportionally short penises mean a high degree of precision is necessary for the sperm to be successfully delivered.

Conservationists have tried a range of methods, from artificial insemination to pornography and viagra, in a bid to encourage breeding among captive pandas.

The Hong Kong park also hosts 34-year-old Jia Jia, the world's second oldest panda in captivity. Its four pandas receive around five million visitors a year, according to Ocean Park. - Sapa-AFP