(AP) -- China's panda population is booming this year thanks to a record number of births in captivity, a rare accomplishment for the endangered species known for being poor breeders.
The most recent addition - the birth of female twins - brought the total number of births this year to 19, surpassing the record of 18 births in 2006, Tang Chunxiang, an expert at the Wolong Panda reserve in Sichuan province, said Tuesday.
Giant panda "Yo Yo" gave birth to healthy twins at the reserve last week.
Tang attributed this year's record number of births to better research on panda nutrition, artificial insemination, genetics and creating a more natural habitat for the pandas to thrive in.
Pandas are threatened by a loss of habitat, poaching and a low reproduction rate. Females in the wild normally have a cub once every two or three years. Fertility rates of captive giant pandas are even lower, experts say. Only about 1,600 pandas live in the wild, mostly in Sichuan in southwest China.
Through artificial insemination, researchers have been able increase the number of pandas in captivity to more than 300 - a number that experts say should remain steady.
"Right now, we're breeding about the same number of pandas each year," said Tang. "We want to steady the numbers to avoid inbreeding since there are so few pandas."
Panda females have only three days a year in which they can conceive - one reason their species is endangered. Some males never succeed at natural breeding, so artificial insemination has become common practice when breeding captive pandas.
Previous efforts to encourage the poor breeders to mate included showing uninitiated males "panda porn," which Chinese scientists have deemed a success and is being used at zoos overseas.
Explore further: China announces first panda from frozen sperm