Britain's only giant pandas failed to mate during their 36-hour window of opportunity, the Edinburgh Zoo said Thursday.
It was "close, but no cigar", the zoo said, after Yang Guang (Sunshine) mounted female panda Tian Tian (Sweetie) several times, without full mating taking place.
The pandas are spending 10 years on loan in the Scottish capital following years of diplomatic negotiations with China that culminated in them arriving in December.
But female pandas ovulate only once a year, with a 36-hour window to fall pregnant and although "the furry pair have hit it off," the clock has run out for the pair this time, the zoo said.
"Results in late last night saw a drop in Tian Tian's hormones and then limited breeding behaviour was seen in both pandas this morning," an Edinburgh Zoo spokesman said.
"As a result, Tian Tian and Yang Guang were not put in together today. Edinburgh Zoo can announce that the panda breeding season for 2012 has now come to an end and both pandas are back on display."
Natural breeding is a notoriously rare occurrence in the endangered species.
Iain Valentine, the zoo's director of research and conservation, said it had been a "fantastic trial run" and there had been a "huge amount of eagerness and attraction" between the pair.
"There was lots of vocalisation and encouragement from our female and physical contact between the two," Valentine said. "He mounted her several times. However full mating did not occur.
"Although both have bred before and have borne cubs with other pandas, they are both still relatively inexperienced," he added.
"We are hugely encouraged by how much the natural sparks flew between the two animals, as, like humans, not all male and female pandas are attracted to each other. 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."