Edinburgh Zoo: Panda mating day arrives EXCITED zoo bosses predict today could be the day for Edinburgh's giant pandas to breed, with Tian Tian's hormone levels peaking within the last 24 hours. The city's most famous couple swapped enclosures again this morning as both showed signs of intensifying breeding behaviour. As temperatures rose yesterday, Tian Tian went into Yang Guang's pool a number of times to cool off, splashing her face and rubbing her scent glands behind her ears. She rolled on the side of the pool as Yang Guang reciprocated the interest by sitting on her bed. He was taken to an area where they could interact through a grate and loudly called out to her in what experts say is "an extremely promising sign." Chemical cues and signals play a major role in breeding as giant pandas are solitary animals and are very much dependent on scent marking as a means of communication between them. Keepers said they hoped Tian Tian would go into season today and the 36-hour conception period would officially begin, allowing them to be re-introduced for the first time since last year's failed attempts. Once the all-important 36-hour window arrives, Tian Tian and Yang Guang will meet several times to have the opportunity to mate. And then, as Tian Tian finally ovulates, artificial insemination will also take place for the first time this year by experts brought over from Berlin. A spokesman said: "We eagerly anticipate the moment her hormones will peak, which should be very soon." Last year's attempts ended in anticlimax as the bears tried but failed to successfully breed during their first year at the zoo. But signs have been positive this year with both showing mating behaviour much earlier than last year. The couple's prolonged courtship has seen Yang Guang perform "pawstands" to prove his virility and mood music piped into their purpose-built £280,000 enclosure. She has previously given birth to twins, but she has not bred with Yang Guang, who has also fathered a cub before. If Tian Tian does fall pregnant, it will be the second half of July or early August before experts at Edinburgh Zoo will be able to tell by using ultrasound scans. The nine-year-old pair arrived from China on a ten-year loan in December 2011. Breeding in captivity has become vital to the giant pandas" survival because of the destruction of bamboo forests in their habitat.