Yang Guang (Sunshine) has been doing handstands against trees, walls and rocks, and scent-marking as high up as possible – known as displays of virility.
Experts at Edinburgh Zoo are hoping Yang Guang and female Tian Tian (Sweetie) could be ready to mate within a month.
At the zoo yesterday, Yang Guang could be seen looking through a closed gate linking his enclosure with Tian Tian's.
He was also reclining on his rock, eating bamboo, increasing his daily intake from 80lb per day to 110lb. This will go up to 220lb as breeding gets closer.
His goal is to drive his weight up, as in the wild he would need enough energy to travel to female territories and compete against other males.
Tian Tian has started calling out to him, which is common during the breeding season.
Picture: Getty Images