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EDINBURGH (Reuters) - A polar bear cub has been born in Britain for the first time in 25 years, the Royal Zoological Society of Scotland said on Wednesday.

Mother polar bear Victoria is believed to have given birth at the Highland Wildlife Park in northeastern Scotland after staff heard high pitched cries in late December.

“We first heard promising noises in the week before Christmas and these have now continued into the new year,” said Una Richardson, the park’s head keeper.

“Because we don’t have sight inside her cubbing box we can’t be sure if Victoria has had more than one cub but we can confirm the birth,” she added.

Polar bears are known for their need for privacy and new- borns are extremely delicate, so the maternity den is closed to visitors at the zoo. The survival of the cub or cubs will not be fully confirmed until March, when bears emerge after winter.

The polar bear breeding season began in March last year, during which time Victoria mated with Arktos, one of the park’s two males.

“While we are absolutely thrilled, we are not celebrating prematurely as polar bear cubs have a high mortality rate in the first weeks of life due to their undeveloped immune system and the mother’s exaggerated need for privacy, with any disturbance risking the cub being killed or abandoned,” Richardson said.

Polar bears are born about 30 cm long and weigh roughly the same as a guinea pig. They emerge blind and do not open their eyes until they are about a month old, depending entirely on their mother’s milk.