Toronto Zoo's giant panda not pregnant after failed breeding attempt

Er Shun rolls in a nest of hay at the Toronto Zoo. (Toronto Zoo / You Tube)

TORONTO -- The Toronto Zoo says one of its star giant pandas isn't pregnant after a breeding attempt wasn't successful.

Er Shun, one of two pandas on loan to Canada from China, was artificially inseminated in April and the zoo says the attempt led to "early signs" of a possible giant panda cub.

But a battery of exams including urinary hormone tests, ultrasounds and even behavioural observations show Er Shun didn't produce a cub.

The zoo says there isn't a pregnancy test for the fuzzy and endangered animals but that its research will be shared internationally to help breeding efforts.

Pandas only have one chance per year when they can breed -- a window lasting one to three days -- and the zoo says they're now keeping an eye on Er Shun to see when her next cycle begins.

The zoo has said the male panda, Da Mao, is too young for breeding, so sperm was flown in from China for the failed procedure.

The pandas will be at the Toronto Zoo until 2018, when they'll move to the Calgary Zoo for another five years.