Watch: Twin giant pandas born in China

Twin giant pandas were born in southwest China on Saturday. Arriving 10 minutes apart, the twins weighed less than 3 ounces each -- small enough for a doctor to wrap his fingers around the future giants.

Their mother, Haizi, gave birth at the China Conservation and Research Center for the Giant Panda at the Wolong Nature Reserve, a 494,000-acre complex in the Sichuan Province. This is the first pair of twin giant pandas born this year.

Staffers at the center said the first cub was a 2.79 ounce female. They do not yet know the sex of the second cub, as Haizi continued to protect it in a tight embrace.

The twins join the estimated 1,900 pandas remaining in the world. Giant pandas are born with white coats, developing their trademark black patches later in life.

According to the Associated Press, giant pandas are only fertile two to three days a year, making it difficult for the endangered species to reproduce. Haizi became pregnant in March.

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    Danielle Elliot is a freelance science editor and reporter for CBS News. She holds an M.A. in science and health journalism from Columbia University and a B.A. in broadcast journalism from the University of Maryland. Follow her on Twitter - @daniellelliot.