It has certainly been an exciting and busy time at Edinburgh Zoo! On 9 April, results from hormone tests of our nine-year-old female panda Tian Tian indicated that she was 11 to 14 days away from coming into season, which only lasts for 24-36 hours once per year.
At first, behavioural signs and further testing made us hopeful that Tian Tian's hormones would peak last Tuesday, 16 April, and the breeding window would begin, but she kept us all on tenterhooks. Each day would begin early with an enclosure swap, where we would put Tian Tian into male Yang Guang's enclosure and vice versa, in order for them to scent mark and smell the other's scents. Tian Tian's behaviour continued to be closely monitored by a team of panda experts including RZSS veterinarian scientists, her keepers and Professor Wang from the China Conservation and Research Centre (CCRCGP). We would also attempt to introduce Yang Guang to her by leading him through a tunnel to her indoor enclosure where they would interact through a grated door. As pandas are naturally solitary animals in the wild, if she was ready to mate her actions would be inviting and she would make chirruping sounds to attract him, if she wasn't ready she would bark at him - her way of telling him to leave her alone.
By lunchtime on Saturday 20 April we suspected she had ovulated (and the 36 hour window had begun) and urine testing confirmed her hormones had started to drop off. While Tian Tian's behaviour continued to become more inviting, it was still apparent that she wouldn't be responsive to Yang Guang and so we decided to not attempt natural mating but skip straight to artificial insemination.
Artificial insemination was always planned for our pandas, even if natural mating occurred, because it best mimics the multiple mating strategy of pandas in the wild. Like IVF, artificial insemination is essentially an opportunity for science to give Mother Nature a helping hand.
Usually a female panda will mate with several males during her breeding window and so by adopting both natural mating and artificial insemination we give her the best chance of falling pregnant. This is also the recommended method used by Chinese panda experts and is important in terms of conservation as the longer a panda goes without falling pregnant the harder it becomes for them to fall pregnant in the future.
The procedure was scheduled for midnight Saturday and took place in the pandas' respective indoor enclosures. Both pandas were sedated as a fresh semen sample needed to be obtained from Yang Guang. At the helm was a team of brilliant, world leading experts in the field of artificial insemination and reproduction management in animals: Professor Dr Thomas Hildebrandt, Dr Frank Goritz and Dr Joseph Saragusty all from the Leibniz Institute for Zoo and Wildlife Research (IZW) in Berlin. They were joined by the RZSS's own top, wild animal veterinarian scientists Simon Girling and Romain Pizzi (who recently performed the world's first bear brain surgery in Asia).
A combination of fresh and thawed frozen semen was used. As there was not enough frozen semen belonging to Yang Guang, semen was augmented with a sample from Bao Bao, another panda. Bao Bao died at Berlin Zoo last year but was previously the last panda on British soil at London Zoo. The use of multiple samples also mirrors the panda's natural mating strategy to maximise the chance of successful breeding.
The procedures were completed by 2am, with Yang Guang up and moving within thirty minutes and back to normal within two hours; Tian Tian took slightly longer. Both are doing very well Yang Guang is back to doing his favourite things: eating and relaxing and Tian Tian ventured outside this morning.
Now it's just a matter of waiting. We won't be able to confirm if Tian Tian is pregnant until late July or early August, with the cub (or cubs!) then due as soon as late August or early September. Pandas practice delayed implantation, where the egg won't implant into the uterus for some time after conception and it's also common for pandas to have pseudo pregnancies, which is why pregnancy can't be confirmed until an ultrasound is performed.