The romance of Valentine's Day may have worked some magic on Edinburgh Zoo's giant pandas.

Experts have revealed the duo could be ready to mate within the next month.

Sweetie and Sunshine – the western names given to the female Tian Tian and male Yang Guang – have started to show changes in behaviour, indicating their readiness to mate soon.

Zoo experts said Yang Guang has recently began doing handstands against trees, walls and rocks, scent-marking as high up as possible – known as a display of virility in the wild.

Meanwhile Tian Tian has started calling out to the male, which is common during breeding season.

Experts are able to predict when both giant pandas are ready to breed by behavioural observation and hormone testing, but to date no hormonal changes have been seen in either panda.

Edinburgh Zoo – where the pandas have lived since their arrival from China in December 2011 – has employed measures to synchronise their breeding cycles.

Iain Valentine, director of giant pandas and strategic innovations for the Royal Zoological Society of Scotland, said the breeding season would probably start in March, but he added: "In reality we could be as little as four weeks away, although equally the big day could still be as far off as eight weeks.

"This year we will combine both natural and assisted reproduction methods."