Despite "natural sparks" flying between them, Edinburgh Zoo's pair of pandas have failed to mate within their optimum window of opportunity - dashing hopes of the patter of tiny panda feet.
Yang Guang (Sunshine) and Tian Tian (Sweetie) met five times on Tuesday and "several times" on Wednesday but have failed to do the deed, the zoo has said.
There could be one last chance on Thursday for the pair - but only if the hormones of the female, Tian Tian, continue to show "receptive" signs to mating.
Keepers opened a "love tunnel" between the bears' separate enclosures on Tuesday after tests showed Tian Tian had ovulated.
At first there were positive, amorous signs , with the giant pandas enjoying their series of encounters.
"Each time the pair met we saw a huge amount of eagerness and attraction between Tian Tian and Yang Guang," said Iain Valentine, the zoo 's director of research and conservation.
"There was lots of vocalisation and encouragement from our female and physical contact between the two. He mounted her several times, however full mating did not occur."
Mr Valentine said the attempted coupling had been "immeasurable" for the bears because they were both sexually inexperienced.
"Both were keen to mate but their inexperience showed. Baby cubs would have been a bonus this year but we have to appreciate that the pandas have only just arrived and have had limited time to settle," he said.
"Overall, we remain very pleased with the outcome of the last few weeks and it has been a fantastic trial run here at Edinburgh Zoo.
"As animal conservationists and scientists, we have learnt a huge amount in such a short time about this captivating species and we look forward to the next 10 years."
The panda pair was flown into Scotland from Ya'an reserve in Chengdu, China, on December 4 last year. They went on show to visitors for the first time on December 16.