Genetic testing has shown a baby polar bear at Tierpark Berlin zoo is the product of breeding between siblings.

A clerical error meant a female polar bear, Tonja, born in Moscow Zoo, was listed as the daughter of the wrong parents, a spokeswoman for Tierpark Berlin told CNN on Wednesday.

Tonja was assigned documents intended for a different female polar bear born at Moscow Zoo two days later, but in fact she had been the offspring of the very same parents as Wolodja, a man polar bear with whom she later mated in Berlin. The group produced infant Hertha, who was born in December 2018.

Suspicions were raised when files were found in Moscow Zoo that listed a different birth date for Tonja, and genetic testing has since affirmed she and Wolodja are siblings.

“That was a big shock for us,” the spokeswoman said, adding that Moscow Zoo was very transparent and informed its counterparts in Berlin if the files were found.

“There was one unfortunate mistake,” she explained.

The bears are a part of the European Endangered Species Programmes (EEP) breeding program for polar bears, which works to maintain the genetic diversity of polar bears in captivity.

Inbreeding reduces genetic diversity, that is”a crucial factor in the long-term survival of species,” in accordance with the European Association of Zoos and Aquaria (EAZA).

“This serious error is a really regrettable setback for the responsible work of the European Conservation Breeding Programme,” Berlin Zoo’s manager, Andreas Knieriem, said in a statement.

“It must now be a matter of understanding from such mistakes and putting our work in all areas even more on a scientific foundation.”

This kind of mix-up isn’t very likely to happen again, as it is unlikely there’ll be two breeding pairs in precisely the same zoo, the spokeswoman said. Additionally, every creature born in Berlin Zoo is given a microchip containing identifying information, including who its parents are.

In the light of the discovery, neither Tonja nor Hertha will have any offspring to the foreseeable future because their family lineage is much better represented in the captive polar bear population than previously believed, ” the spokeswoman said.

But, there is a possibility that both bears will probably be bred in the future, she added.

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“Our mission is to keep the genetic diversity as large as possible,” said the spokeswoman.

Hertha is a”joyful and healthy keep” that will stay at the zoo along with her mum, she included. Wolodja has moved into a different zoo in the Netherlands.

Tonja also had a baby called Fritz at November 2016, but he died of liver inflammation in March 2017. Fritz was also fathered by Wolodja, but experts have said it’s very unlikely that inbreeding was accountable for his departure, ” the spokeswoman said.

UK campaign organization Bear Conservation estimates that there are more than 300 polar bears in captivity around the globe.