It’s showtime for a zoo ‘show-stopper’

Zhen Zhen, the newest charismatic mega-vertebrate at the San Diego Zoo, was climbing a downed tree branch in her grotto Friday when she went wobbly and plopped to the ground, 3 feet below.

Not to worry giant panda-philes, it’s all part of the maturation process. Plus, if anything had gone seriously amiss, her mother, Bai Yun, was nearby having a bamboo breakfast.

After four months of being visible only on the panda cam on the zoo’s website, Zhen Zhen (pronounced jun-jun) is to go on public display today.

There are many small things not known about pandas, but there is one large thing that is well-documented: Giant pandas are the most popular animals ever displayed in U.S. zoos. To gather a crowd, get one of these animals with the hypnotic black-and-white fur.

Only four U.S. zoos have pandas: San Diego, Memphis, Atlanta and the National Zoo in Washington, D.C. San Diego has the most pandas, with four.

Under a complex loan agreement with the Chinese government, Zhen Zhen, born in August at the zoo, will someday go to live in China. But that day is years away.

On Friday, she climbed, she tumbled, she lay on her back, she pestered her mother, she did all the things that zoo patrons expect.

Kathy Hawk, the zoo’s senior panda keeper, has tended to all the pandas, the adults shipped from China and the four cubs born here. Under the agreement, China retains the rights to any cubs born at the San Diego Zoo, and they must be sent to their ancestral home after three years.

“Zhen Zhen is very reminiscent of Hua Mei,” Hawk said. “She’s definitely a show-stopper.”

To the panda constituency, a comparison to Hua Mei is the gold standard. Born at the zoo in 1999, she was an instant favorite.

Her departure to China in 2004 occasioned much local sorrow. Fans still besiege the zoo for updates. The zoo’s website informs that Hua Mei has given birth to three sets of twins at the Wolong Giant Panda Research Center. A male cub also had been sent to China.

At 17 pounds, Zhen Zhen is heavier than the other three cubs born at the zoo were at her age. For another year, her nourishment will be from nursing off of 220-pound Bai Yun.

At the beginning, Zhen Zhen will be out for viewing only from 9 a.m. to 11 a.m. As the cub gets more comfortable with crowds and picture-taking, the hours might be extended.

Zhen Zhen’s debut has been much anticipated, as comments on the zoo’s panda blog attest. Panda watchers from Southern California, Arkansas, Texas, Michigan, New York, Iowa and San Francisco have checked in.

The pandas are so popular that the zoo was motivated during the October wildfires to put a statement on its website, www.sandiegozoo.org, assuring patrons that the panda exhibit was not in danger. The fires did not come within miles of the zoo, but the panda constituency was clamoring for reassurance.

Although Zhen Zhen is the latest attraction, the other pandas -- the adult male Gao Gao and young female Su Lin -- have their own followings. Veteran panda followers also watch Bai Yun’s mothering skills. Keepers are ready for the questions.

“Bai Yun has being a mother down pat,” Hawk said.

tony.perry@latimes.com