Edinburgh Zoo giant panda artificially inseminated
Edinburgh Zoo bosses have embarked on a fresh attempt to see if the UK's only female giant panda can produce a cub.
Tian Tian was artificially inseminated on Sunday evening after tests showed she had reached her short breeding window.
Experts carried out the procedure after the zoo's male panda Yang Guang was unreceptive to natural mating.
Semen from Yang Guang was used in the procedure, which was carried out by zoo vets and colleagues from China and Germany.
Keepers have inseminated Tian Tian on three previous occasions but she has failed to produce a panda cub since arriving in the UK at the end of 2011.
Writing on Monday on the website of the Royal Zoological Society of Scotland (RZSS), which runs Edinburgh Zoo, director of giant pandas Iain Valentine said: "Yesterday afternoon, Tian Tian's behaviour and the scientific results from the University of Edinburgh's hormone testing of her urine showed she'd reached her short breeding window, after what had been a very slow climb to peak accelerated with some speed.
"Although this is all completely normal female panda behaviour, this year Tian Tian surprised us in a few ways, coming into season much later than she ever has before since her arrival in Scotland (last year she reached her breeding window on March 26, then in previous years her dates fell within April) and ovulating on day 10 instead of her usual day 13."
He said a plan of action was put in place but "unfortunately Yang Guang wasn't receptive to natural mating this year", despite Tian Tian's behaviour suggesting she wanted to be mated.
"In the early evening, we then prepared to give nature a helping hand by performing an artificial insemination procedure," Mr Valentine said.
"With our Chinese colleagues from the China Conservation and Research Centre for the Giant Panda (CCRCGP), Tian Tian was implanted with semen from our male Yang Guang by experts from the Leibniz Institute for Zoo and Wildlife Research (IZW), a complex procedure which was undertaken with great skill."
Zoo chiefs said it will be some time before they know if Tian Tian has conceived and gone on to become pregnant.
The giant panda enclosure is currently closed to visitors and will remain so until Thursday.
"We continue to believe that it's important biologically for Tian Tian, a female in her prime, to breed and reproduce and add to a vital ex-situ population outside of China," Mr Valentine added.
"If we can successfully assist Tian Tian to carry to full term, we have no doubt that she'll be an excellent mother and both our male and female's genetics will be preserved in future giant panda generations."
Tian Tian (Sweetie) and Yang Guang (Sunshine) are the only giant pandas living in the UK.
The black and white bears arrived on loan from China in December 2011 and are due remain at Edinburgh Zoo for a decade.
There were hopes that a panda cub would be born last year after Tian Tian was inseminated. But the zoo said in August that they believed Tian Tian had ''resorbed her pregnancy in late term'', as is common among giant pandas.
Panda reproduction is a notoriously tricky process, with females only ovulating once a year.