BBC News - Q&A: Edinburgh's giant pandas 21 April 2013 Last updated at 11:06 Since they took up residence in December 2011, they have become two of Edinburgh's best-known characters. Yang Guang and Tian Tian, the giant pandas, have attracted visitors from around the world and there's no sign of interest waning. Hundreds of people have been joining panda tours in Edinburgh Zoo each day and much of the excitement, of course, arises from the hope that the giant pandas will breed successfully. Experts at the zoo have now carried out artificial insemination on Tian Tian. Our correspondent Colin Blane has been following the progress of the panda pair since they arrived in Scotland from China. Here's his panda fact-file: Yes, there's a very good chance. They were unsuccessful during last year's brief mating season but Tian Tian has given birth to cubs before and Yang Guang has also fathered cubs. The pandas' keepers will only find out if Tian Tian is pregnant in July when they'll give her an ultra-sound scan. Pandas normally mate in April or May and the female gives birth in August or September. Both Yang Guang and Tian Tian were August cubs. Unusually, though, pandas sometimes have what's called delayed implantation which means the length of time from mating to giving birth can be extended because the female panda's body may respond to adverse conditions. Pandas quite often have twins, although, in the wild, the mother would decide quite early which cub was stronger and the other wouldn't survive. In captivity, every effort is made to rear both cubs. And Tian Tian has had twins in the past. Edinburgh Zoo has a financial arrangement with the Chinese authorities. The zoo will keep Yang Guang and Tian Tian for 10 years at an annual fee of £600,000. As part of the deal, any cubs will remain in Edinburgh for two years before being sent back to China. At that age, cubs would be independent of their mothers in the wild. It's true that the number of giant pandas is very small, perhaps 1,600 in the wild and another 300 in zoos. One important reason for their decline has been destruction of the bamboo forests where they live in south west China. The Chinese recognise that pandas need to be able to move around freely and so are trying to link up existing areas which are presently broken up by roads or railways. It's also true that female pandas will only mate during a 36-hour window each year. In the wild, they might have several partners in that period. In captivity, zoos are using artificial insemination to replicate those breeding opportunities. Some ecologists have argued that pandas are already doomed to extinction because their limited diet makes it impossible for them to adapt. Optimists say they've already survived for eight million years - considerably longer than humans. There was considerable diplomatic effort on the part of the Scottish and UK governments, with the zoo also making its own case. Edinburgh Zoo argued that they had suitable staff and could call on outside experts who would work together on panda breeding and conservation. Since the agreement was reached, staff from Edinburgh have been working closely with Chinese panda specialists. Scottish keepers have been to the panda breeding centre near Chengdu in Sichuan Province and panda conservationists from China have come to Edinburgh. Aside from conservation, the giant pandas represent a potential financial lifeline for Edinburgh Zoo which had been suffering falling visitor numbers before Tian Tian and Yang Guang arrived. In the first year of the Edinburgh pandas, the zoo enjoyed a 50% increase in its visitor numbers, more than enough to cover the cost of payments to China.