BEIJING, May 5 (Xinhua) -- The flood of holidaymakers in Beijing has forced one of the world's most endangered mammals to work overtime during the week-long "golden holiday".

Giant pandas at the Beijing Zoo can have some peace and quiet only after 6:30 p.m., 30 minutes later than usual as an average 100,000 people are pouring in daily, said Wang Baoqiang, vice general manager of the zoo.

All animals and employees have to work overtime as the zoo has extended its opening hours during the first week of May.

"There's been a surge of tourists starting from last Monday, particularly people from outside Beijing," said Wang. "But it's crucial to keep the animals healthy and make sure their biological clock is not disturbed."

More than 200 zoo workers are on duty each day to take care of the animals and people. "This is four times as many as on normal weekdays because we need to make sure the visiting crowds are safe,too," said Wang.

Nearly all Beijing tourist destinations have placed extra security staff for safety considerations.

At the "Happy Valley", a Disneyland-style entertainment center in eastern Beijing, young security guards have learned to conjure up ducks out of balloons to amuse the long queues of children waiting impatiently for their turns on the roller coaster.

The center receives a record 30,000 people daily, which means people have to wait two to three hours for the most popular games.

Sightseeing in Beijing is anything but comfortable these days with the jostling crowds and sizzling temperature that has topped 30 degrees Celsius, the highest in the past 40 years.

The Summer Palace, a former imperial garden and Beijing's largest park, received 280,000 visitors in the four days between May 1 and 4.

The Forbidden City received a record 114,800 people on May 2 but the number nearly halved on Friday to 63,600.

Meanwhile, an average 73,000 people are touring the Badaling Section of the Great Wall daily.

The Quanjude Group, a centennial chains restaurant known for Beijing roast ducks and a main stop-off for first-time visitors to Beijing, sold nearly 20,000 ducks in the first three days of the golden week.

More than 60,000 diners ate at its restaurants between May 1 and 3, spending 12 million yuan (1.5 million U.S. dollars), company sources told Xinhua.