ZOO keepers have started monitoring giant pandas Tian Tian and Yang Guang as mating seasons gets underway.
Edinburgh Zoo hopes the pair will produce a cub this year as they start to show signs they are ready to breed.
There was disappointment last year when they did not mate, and although Tian Tian was artificially inseminated, she lost her foetus at late term.
Panda reproduction is a notoriously complex process, with females only ovulating once a year.
Iain Valentine from the Royal Zoological Society of Scotland (RZSS), which runs Edinburgh Zoo, said: “Tian Tian and Yang Guang are both in great health and condition and things are progressing nicely.
“The giant pandas are clearly showing an increased interest in one another, both pandas are fairly regularly scent marking now and we’ve also seen food intake increase in both pandas as they seek to drive their body weight up - all fantastic instinctive pre-breeding behaviours.
“Similar to last year, alongside our own experts, RZSS is working together with a number of global colleagues on the complex science that goes on behind the scenes. Natural mating will be attempted, likely followed by artificial insemination as recommended by our Chinese colleagues.”
Experts have begun the daily monitoring of Tian Tian’s hormones which will signal when she is ready to breed. She will then have a period of just two to three days to get pregnant.
Mr Valentine said: “As of Christmas 2013, we again began to collect urine samples from Tian Tian. These are being picked up and analysed so that we can monitor two key hormones for breeding purposes - progesterone and oestrogen.
“We’re currently just waiting for the all-important crossover of hormones in Tian Tian and then when this happens it means breeding is roughly seven to 14 days away. This week we moved to analysing Tian Tian’s urine samples each day, so it’s a case of watch and wait.”
The panda gestation period is typically five months and one or two cubs will be born.