Chengdu , China ( CNN ) -- The researcher dressed in blue plastic smock , slippers and gloves is having a tough time getting his work done . Every time Zhang Zhen sets up his camera on a tripod in an effort to document the behavior of one of the panda cubs scattered on a grassy hillside , one particularly frisky baby panda comes wobbling towards him , interrupting his shoot . `` Mumu ! '' he yells in frustration , as the four-month old cub rears up on her hind legs , lunging towards him . He picks Mumu up and deposits her at the opposite end of the enclosure . `` I 'm not sure why she 's been all over me like this . I think she 's excited today , '' Zhang says . Mumu is the oldest of fourteen baby pandas that were born last summer here at the Research Base of Giant Panda Breeding in Chengdu , China . China 's panda experts have improved the science of breeding and raising members of this endangered species in captivity . The proof of their success is in the baby panda enclosure , where visitors can watch as the newest generation of pandas takes turns napping , playing and exploring their outdoor habitat . The fuzzy young cubs are still shaky on their feet , and often trip and roll down the enclosure 's slight incline . While two cubs wrestle , another tries to climb a tree and then tumbles onto its back , slowly performing a backwards somersault , much to the amusement of onlookers . Giant panda Tian Tian likely miscarried . `` There are new breakthroughs , so that 's why the panda population has continued to increase , '' said Deng Tao , the chief zoo keeper at the Chengdu base . When Deng first began working at the base 12 years ago , he said there were only 20 pandas here . Today , the center is responsible for more than 100 animals . Deng recently returned from the Atlanta Zoo , where he spent months assisting with the birth and care of twin cubs who were born there last July . `` Now we have new technologies that can very accurately identify when a panda is ovulating and do artificial insemination during a precise point in the [ reproductive ] cycle , '' Deng explained . On its website , the Atlanta Zoo credited Deng and his colleagues in Chengdu with developing a technique using incubators and taking turns rotating twin cubs with the mother to better ensure the newborns ' chance of survival . `` Before when a panda had twins , the mother panda could only take care of one cub so we have resolved the issue of having twin pandas and helping them to integrate , '' Deng said . The next big challenge facing China 's panda keepers involves reintroducing captive animals back to the wild . `` We have made a training base to return pandas to the wild , '' Deng explained . `` Once they are mature and able to forage for food and hide from danger , then we will release some pandas . '' National Zoo 's panda cub is healthy , officials say . Wildlife conservation groups say China 's effort to save the giant panda from extinction is a rare success story . According to the World Wildlife Fund , as of 1988 there were only around 1,000 pandas left living in the wild . In 2004 , that number was estimated to have grown to 1,600 wild pandas . More recent panda census statistics are not yet available . `` The government put the resources [ into conservation ] . They 've actually set up some mountains just as a habitat for the panda , '' said May Mei , the chief representative in China for the conservation group WildAid . China has lavished resources on the conservation of the giant panda- rather than on some other indigenous endangered species- in large part because the animal is such an important national symbol . `` They are a treasure for people in China , '' Mei said . The breeding center in Chengdu is also something of a panda theme park . Excerpts from the animated DreamWorks film `` Kung Fu Panda '' play on a giant screen at the entrance to the facility , which receives more than a million visitors a year . Inside , tourists travel in panda mobiles , decorated with the cartoon movie 's main character , Po the Panda . In addition to stuffed animal pandas , souvenir shops offer a variety of hats , ear muffs , and even fuzzy nunchucks decorated with the panda 's distinctive black-and-white panda patterns . Visitors walk along paths , gazing and taking photos of pandas in large outdoor pens . The animals seem to completely ignore humans . In one pen , a 25-year-old male named Shi-shi lies on his back , gorging himself on bamboo which he holds in his front paw with the help of what trainers call the panda 's `` pseudo-thumb . '' Other adults seem to spend much of their time fast asleep in their enclosures . But the big lumbering animals clearly have charisma . `` They 're cute man ! '' says Chris Delbene , a 21-year-old university student from Orego who is studying Chinese in Beijing . `` They live a great lifestyle , play all day , eat , sleep . '' What 's cuter than one baby panda ? Panda twins ! CNN 's Steven Jiang contributed to this report .
China 's panda experts improved breeding pandas in captivity . 12 years ago , Chengdu zoo keeper had only 20 pandas , now center has more than 100 animals . Challenge is reintroducing captive pandas back into the wild .