Tokyo's Ueno Zoo said Tuesday that two giant pandas have mated, sparking hopes for a cub.
Zoo staff saw the female Shin Shin and male Ri Ri, both 7 years old, mate Monday evening and again Tuesday morning.
The mating period is expected to continue for a few days more, and the zoo will put them together again in the same enclosure.
The two pandas have been removed from public view since last Thursday because Shin Shin appeared ready for mating. The mating season for giant pandas occurs just once a year, during which time females are able to conceive during a very short window of time.
"The chances of pregnancy will grow the more they mate, so we will continue to watch their behavior," said Kazuomi Nishikiori, head of the zoo's educational activities. A cub was born to the pair last July, the first one at the zoo in 24 years, but it died of pneumonia six days later.