Story highlights Giant panda twins born Monday evening

Last panda twins born in U.S. were in 1987, zoo says

Twins would go on public display in late fall

Fewer than 2,000 giant pandas thought to survive on planet

America has its first panda twins in 26 years.

The tiny pair were born to mother Lun Lun, a 15-year-old giant panda, at Zoo Atlanta on Monday, the first arriving at 6:21 p.m. and the second at 6:23 p.m. The zoo did not immediately know the gender of the cubs.

The twins are the first for Lun Lun, who has two other offspring at Zoo Atlanta, and are the product of artificial insemination. Their father is 15-year-old Yang Yang, also a resident at Zoo Atlanta.

"We're thrilled to welcome Lun Lun's and Yang Yang's twins. This is a success we share with all of our fellow zoological organizations working to understand and protect this iconic species, and we share our joy with our local community and with our colleagues in China," Raymond B. King, president and CEO of Zoo Atlanta, said in a statement.

The pink-colored twins -- black patches of hair will begin to appear in a week or two -- were separated shortly after birth, with one staying with Lun Lun and the other being cared for in the zoo's nursery.

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"Twins are an entirely new scenario for Lun Lun, Zoo Atlanta and our animal care teams, who will no doubt be extremely busy over the next few months," King said.

The zoo said twins typically weigh less than single-born panda cubs with a high risk of mortality. A single panda cub typically weighs just 3 to 5 ounces at birth, according to the Smithsonian National Zoological Park.

Twins are not unusual for pandas, Zoo Atlanta said in a statement, but in the wild the mother will usually only care for one of them. That is why they were separated, but the zoo said they may rotate them in Lun Lun's care over the next few months.

The public can expect to see the panda twins in the late fall, the zoo said. Their father and two brothers, Xi Lan, 4, and Po, 2, will remain on display.

Fewer than 2,000 giant pandas remain on the planet, according to the Smithsonian. Of these, 300 are in zoos and breeding centers, mostly in China, and about 1,600 remain in the wild in mountain forests of central China.