Mei Xiang at Washington's National Zoo, Jan 201, 2011
Mei Xiang at Washington's National Zoo, Jan 201, 2011

WASHINGTON - The National Zoo's giant panda Mei Xiang is showing signs of being pregnant, the Washington zoo said on Monday, in a good development for the endangered species.

Mei Xiang, a star tourist draw in the U.S. capital, has shown a secondary rise in her urinary progesterone levels starting on July 20, the zoo said in a statement.

The increase "indicates that she will either have a cub or experience the end of a pseudopregnancy within 30 to 50 days," the statement said. Mei Xiang was artificially inseminated on April 26 and 27.

The procedures used frozen sperm from Hui Hui, a panda living in China, and fresh sperm from the National Zoo's Tian Tian, it said.

Veterinarians are monitoring changes in her reproductive tract and evaluating her for signs of a fetus. The only way to determine if a giant panda is pregnant is to detect a fetus using an ultrasound, the statement said.

Mei Xiang is showing behaviors at the David M. Rubenstein Family Giant Panda Habitat in line with a rise in progesterone. She is nest building, spending more time in her den and sleeping more and eating less.

Giant pandas are one of the world's most endangered species. Their natural home is in a few mountain ranges in central China.

There are about 1,600 giant pandas known to be living in the wild and some 300 in captivity, mostly in China.