While the giant panda is known for its finicky breeding habits in captivity, its distantly-related cousin, the red panda is known to breed particularly well in zoo.
As such, the Smithsonian National Zoo welcomed four red panda cubs this summer -- bringing the total number of red panda births here to more than 100 cubs since 1962.
But while the zoo is celebrating these bright-eyed and bushy-tailed arrivals, they're also suffering a bit of disappointment.
Staff had suspected the zoo's resident giant panda, Mei Xiang, was pregnant; but the hormonal fluctuations they had been monitoring turned out to be merely signs of a false pregnancy.
Two of the cubs were born at the National Zoo and two more were born at the zoo's sister facility in Virginia. All four cubs are female.
The two pictured above are the offspring of the National Zoo's proud red panda parents, Shama and Tate.
Shama gave birth in her den on June 17. When she didn't respond to the usual calls from zoo keepers, the staff suspected that she had given birth.
A quiet squeal from the den was the first hint of cubs. But it would take another week before the zoo keepers were able to do a "cub check" to confirm.
BIG PIC: Red Panda Cub Born at the National Zoo
Tiny from birth, red pandas generally grow to be seven to 14 pounds. In comparison, giant pandas grow to about 200 pounds.
These cubs will spend the next 90 days in the den and won't leave their mothers for up to year.
Red pandas are considered a vulnerable species by the International Union for Conservation of Nature. There are estimates that the mature wild population is as low as 2,500 individuals.
The red panda's particularly bushy tail helps it stay balanced as it climbs trees.
And, while it's predominantly a reddish-brown color to match its surroundings, it inhabits some of same territories as the giant panda: China, the Himalayas, and Myanmar.
They also have a similar diet -- with a few additions. Red pandas mainly feast on bamboo but also eat berries, blossoms, and bird eggs, according to the National Zoo.
Veterinarians are careful to wear gloves and take necessary precautions when handling the cubs.
Many times staff will wear a second set of gloves that have been rubbed with nesting material and the mother's feces in order to cover their own human scent.
Each of the cubs has gotten a clean bill of health from zoo veterinarians.
Mei Xiang, the zoo's female giant panda had her sixth psuedopregnancy -- a common occurrance for pandas.
Mature pandas ovulate once a year and either conceive or don't, but they still experience the same signs of pregancy: decreased appetite, excessive grooming and spending more time in the den.
Mei Xiang had also been showing signs of hormonal changes in her urine, but veterinarians had been unable to observe a fetus during ultrasound exams.
Now, after several weeks of her hormone levels declining, zoo keepers can officially declare it a psuedopregnancy.
Panda births are rare in captivity. Mei Xiang gave birth to one cub in 2005.
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