Giant Panda Estrus FAQs
Breeding season for giant pandas is usually in the spring from March to May. Although the breeding season lasts for several months, a female giant panda is only capable of conceiving a cub for 24 to 72 hours once a year. In the wild, male giant pandas may breed with multiple females throughout the breeding season.
When the breeding season is approaching, giant pandas are generally more restless than at other times of the year. They can frequently be seen patrolling their territories, investigating scent markings left by other pandas, leaving scent marks, climbing trees, playing in water and making bleating and chirping vocalizations.
Males will mark their territories doing a behavior called “urine hopping” (which looks like they are hopping on one foot as they urinate). They will also attempt to make their urine marks as high as possible on trees and other structures. When they do this they look like they are doing a handstand. They will bleat to females to show their interest.
Female pandas will bleat to the males and eventually make a “chirping” vocalization to show interest. If a female encounters a male, she will raise her tail and walk backwards toward him to indicate she is receptive to breeding.
Tian Tian usually becomes very playful and restless during breeding season. He spends much of his time scent-marking, playing in water, patrolling his yard and vocalizing to Mei Xiang.
Mei Xiang’s behavior can sometimes be more subtle than Tian Tian’s before breeding season. She will spend more time scent-marking and investigating Tian Tian’s scent marks. She also paces and spends time in the pools and water features in her enclosures. Generally, she does not spend very much time interacting with Tian Tian unless she is in estrus (the very short window when she is able to conceive a cub). Her vocalizations towards him become more friendly when she nears estrus.
Female pandas will make a “chirping” vocalization to attract any nearby males and indicate she is ready to breed. If she encounters a male, she will raise her tail and walk backwards toward him to indicate she is receptive to breeding. She will do this towards Tian Tian at the window between the yards.
Yes, she has in the past, but she was nursing a cub each time. Giant panda breeding season is typically from March to May.
Mei Xiang is near the end of her reproductive life cycle, but there are pandas who have had cubs when they were older than she is now.
Behavioral cues are one way we determine when breeding season has arrived. Since the window when Mei Xiang is able to conceive a cub is very short (24 to 72 hours), our endocrinologists at the Smithsonian Conservation Biology Institute monitor the levels of estrogen and progesterone in her urine. When they see her levels of estrogen rise, that means Mei Xiang is in estrus. After her estrogen levels have peaked, that indicates that she is ovulating. Our reproductive physiologists also monitor physical changes that indicate Mei Xiang is getting ready to breed.
We regularly collect urine samples. The samples are sent to the Smithsonian Conservation Biology Institute for analysis weekly, but increase in frequency of analysis as Mei Xiang gets closer to estrus. When she enters peak estrus, our team stays overnight so we can collect all of her urine so we can predict her ovulation.
We collect it with a syringe from the floor of Mei Xiang’s enclosure. She tends to urinate in the same spots each day.
Why do you not give Mei Xiang and Tian Tian the opportunity to spend time together as soon as Tian Tian begins showing interest in Mei Xiang?
Giant pandas are solitary and adults do not spend much time interacting outside of the breeding season. If we were to allow Mei Xiang and Tian Tian to spend time together before Mei Xiang were ready to breed, they would likely be aggressive toward each other. In the wild, a female would avoid males until she is ready to breed.
Mei Xiang is capable of conceiving a cub once she has ovulated (after her estrogen levels have risen, peaked and have started falling). When they are back to normal levels, or what our scientists call “baseline levels”, her estrus and breeding season is finished. Our scientists usually start to see her estrogen levels rise for several days before they peak. After they peak, her hormone levels usually return to normal within 72 hours.
If Mei Xiang shows interest in breeding with Tian Tian we will give them the opportunity to spend time together and attempt to breed naturally. Our panda team, which includes Smithsonian Conservation Biology Institute scientists, Zoo veterinarians and keepers, will perform one or more artificial inseminations in addition to natural breeding.
Female giant pandas experience the same behavioral changes and hormonal changes if they are pregnant or pseudopregnant (not pregnant). Even if Mei Xiang is not pregnant, she will still build a nest, spend time body-licking, cradle objects and sleep often. Her levels of progesterone will rise and fall just as they would during a real pregnancy. The only way to definitively determine if a female is pregnant is to detect a developing fetus on an ultrasound.
A pseudopregnancy mimics a real pregnancy, but instead of giving birth at the end of it, a giant panda returns to normal behaviorally and hormonally.
They have been given the opportunity to breed naturally nearly every breeding season, but our panda team has never observed successful breeding from them.
We separate Mei Xiang and Tian Tian immediately after breeding attempts to prevent any aggression. Males often get aggressive towards females once their hormones start to decrease.
We don’t know definitively when Mei Xiang will be past breeding age. Based on the data from scientists in China and other zoos with pandas, females can breed until their early twenties.
Mei Xiang is no longer ovulating, but she and Tian Tian are still vocalizing to each other and spending time at the mesh howdy windows. Is that normal?
Yes, that’s normal. Sometimes it can take a few days for Mei Xiang’s hormones to return to baseline, and during those few days she may occasionally choose to interact with Tian Tian through the howdy windows. By that time, Tian Tian has usually lost interest in her and his vocalizations are not friendly. He is able to sense that she is no longer in estrus.
Panda gestation length ranges from 90 to 180 days, with an average pregnancy lasting 135 days. This wide variation in gestation occurs because the fertilized egg usually floats freely in the mother's uterus before it implants and begins developing. Once the embryo is attached to the uterine wall, its development continues until a panda is born; newborn pandas are blind, very small and without almost any fur. A newborn panda is about 3 to 5 ounces. In American black bears, the actual period of time the embryo is developing after implantation is about eight weeks. Pandas' actual development time is probably similar. Much of a panda's physical development occurs after birth.