Ri Ri & Shin Shin were take off display during the first week of February 2016 at Tokyo’s Ueno Zoo.
Ri Ri was increasingly interested in Shin Shin, after hormonal analysis indicated Shin Shin was approaching the peak of her heat.
The 10-year-old pandas were given a choice to use two rooms to mate.
Specialists at the zoo said the changes they had observed in the behavior of both of pandas raised hopes they would conceive.
They said Ri Ri showed strong sexual interest in Shin Shin, evinced by his active movements, his bleating at Shin Shin, and by scent-marking. Shin Shin also responded to Ri Ri’s bleats and dipped parts of her body into water.
But despite the signs of estrus, the two did not frequently exchange bleats or chirping sounds and did not copulate. The zoo concluded that Shin Shin’s signs of estrus were not as strong as those observed during the peak, and thus she was not ready to mate.
The zoo officials said they would be watching the pandas for further signs of an estrus cycle based on results from behavioral and psychological analysis, but were not considering artificial insemination in further attempts.
In 2012, Shin Shin, who was brought from China five years ago, gave birth to a cub that died from pneumonia about a week later. She also had a phantom pregnancy the following year. The pandas have not bred since.