Shin Shin, the female giant panda at Ueno Zoo, is highly unlikely to be pregnant, officials at the Tokyo facility said Tuesday, saying she isn't showing the conditions usually observed before pandas give birth.
Shin Shin has been removed from public viewing since June 4 because zoo workers suspected she might be pregnant. She and male panda Ri Ri, both 7 years old, were confirmed to have mated in March, raising hopes for a cub.
"We can't observe any major changes to her nipples or genitalia. Usually the breasts get firm or the genitalia is enlarged right before the delivery," said Kiyoshi Nagai, the zoo's public relations chief, said at a news conference.
Nagai added that Shin Shin's progestational hormone level was low enough for delivery with 1.0 nanogram per milliliter as of last Thursday.
He said the zoo hasn't completely ruled out the possibility that Shin Shin is pregnant and added that observations will continue for the time being.
False pregnancies are a physiological phenomenon, not a disease, according to the Tokyo Zoological Park Society. Once an egg is released, a panda goes through the same process as in a pregnancy, even it doesn't lead to delivery of a cub.
The pair of giant pandas had a cub last July, the first time in 24 years a cub was born at Ueno Zoo, but the newborn died of pneumonia just six days after birth.
The two animals were loaned by China in 2011. Public viewing began at the zoo that April 1 after their debut was delayed by the Great East Japan Earthquake on March 11.
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