BUDAPEST, Nov. 13 (Xinhua) -- A golden-bellied mangabey baby, a real rarity in the world of zoos, was born on Oct. 22 in the Budapest Zoo, the zoo's press officer said on Tuesday.

"The golden-bellied mangabeys can be seen nowadays in their inner heated place where, due to the birth of the baby monkey, a temporary cordon has been erected in front of the glass wall," Zoltan Hanga, the spokesman of the zoo explained. "This does not hinder the observation of the animals."

The golden-bellied mangabey (Cercocebus chrysogaster) is a social Old World monkey found in swampy, humid forests south of the Congo River in the Democratic Republic of the Congo.

It was previously considered a subspecies of the agile mangabey. Little is published about the species and its behavior has only been studied in captivity.

Because their habitat is difficult for researchers to find and due to their hidden lifestyle, there is no information on the exact size of the wildlife population of the species.

It can only be assumed that the population is declining. The species has been added to the category: "date deficient" by the International Conservation Union (IUCN).

"Both the keeping and the breeding of golden-bellied mangabeys have a decade-long history in the Budapest Zoo," Hanga added.

"In the world of zoos, golden-bellied mangabeys are a real rarity. Of the thousands of zoological gardens in the world, only 12 zoological gardens have golden-bellied mangabeys, altogether 27 specimens," Hanga said.

The Budapest Zoo and Botanical Garden is the oldest zoo park in Hungary and one of the oldest in the world. It has 1,072 animal species and is located within Varosliget Park, unusually for a zoo, since it is in the center of the city. The zoo opened its doors in August 1866. The park has 1 to 1.1 million visitors every year.