Mating season only occurs once a year, between February 15th and march 30th, period during which the female panda is fertile for 48h.
During the heat of the female our panda couple meets, living the remaining time in a solitary way, as in their natural milieu.
If pandas do not mate naturally, an artificial insemination could be made. This one being part of a research program for the conservation because the species is threatened within nature.
If the fertilization succeeds, the embryonic diapause starts. But what is the diapause ?
Diapause is an almost systematic phenomenon in all ursids. The oocyte is not nested and therefore there is no hormonal impregnation. Embryonic development is then stopped.
The end of the diapause happens by behavioral changes (exhaustion and lose of appetite) and hormonal changes (hormonal increase observable by daily samples of urine and weekly analysis) that show the beginning of the gestation or pseudo-gestation.
During the period of gestation or pseudo-gestation, of a duration of 3 to 6 weeks, the signs are similar. At this stage, it is impossible to know whether the female is pregnant or not.
To have a confirmation of the gestation, the only way is to check visually with an echography the presence of an embryo. This one is only detectable 3 weeks before birth. Sometimes, the baby is so small that it is only perceptible at the extreme end of the gestation.
24h to 48h before birth, the level of progesterone of the female panda drops down. It decreases slower if the female doesn't give birth. It was therefore in period of pseudo-gestation.
If it is really in gestation, therefore, 24h after hormonal fall, a 150g baby is born. A litter can also be composed of 2 to 3 babies!
The female panda and its baby are then sheltered within an inside box. The visitors will be able to see them about 3 months after birth.