For the past two weeks, zookeepers have been peeping into the polar bear “birthing cave” every morning via a surveillance monitor. Yesterday, they got a surprise: next to mother Tonja lay two tiny cubs the size of guinea pigs.
These are the first polar bear cubs to be born at Tierpark Berlin in 22 years. The twins’ parents are six-year-old Tonja and four-year-old Wolodja.
Wolodja and Tonja mated several times between March and June. It is not possible to determine the exact gestation period of a polar bear. The embryo begins to develop from the fertilised egg once the summer is over, following a period of “dormancy”. Like polar bears in their natural habitat, females in zoos withdraw in the autumn to have their babies. The cubs are born when they are only about 30 cm in size and are still deaf and blind.
While visitors can still see daddy Wolodja in the outdoor area, mother Tonja and her cubs are hidden away in the birthing cave.
“The mortality rate for young polar bears is around 50 percent, and it is particularly high in the first ten days,” explains Zoo and Tierpark Director Dr Andreas Knieriem. “What’s more, Tonja lacks experience as this is her first birth. Up to now, all successful breeding attempts at the Tierpark have resulted in the birth of two cubs, but only one of the two has ever survived to maturity. So we really have to cross our fingers over the next two weeks. But even the successful rearing of one cub would be wonderful.” For the Tierpark staff, the birth is extremely exciting despite the critical phase that lies ahead. It shows zoo keepers, vets and curators that both bears are fertile and that Tonja has good maternal instincts and feels comfortable and safe in the birthing cave.
The curator responsible for the bears, Dr Florian Sicks, is particularly thrilled about the surprise: “All the signs we have so far are very promising. Tonja stays close to her babies at all times and keeps them warm against her body. This birth is also important validation of the work of the zoo keepers, as it shows that they have gained the bears’ complete trust.”
Over the coming days, no one will approach the birthing cave. Mother and cubs require total peace and privacy to give them the greatest chance of success. Tonja and the other female polar bear Aika have put on enough fat reserves to live off. The polar bears are not fed during this resting period.
The young family is currently not visible to the public. Much like in the bears’ natural habitat, the mother will not emerge from the birthing cave with her cubs until spring.
Polar bears at Tierpark Berlin
Tonja was born on 14 November 2009 at Moscow Zoo.
Wolodja was born on 27 November 2011 and originates from the other Moscow Zoo breeding group.
Aika was born on 24 November 1980 in Katowice (Poland) and is currently the oldest polar bear in captivity.
Polar bear births at Tierpark Berlin
The first polar bear to be born at Tierpark Berlin arrived on 7 November 1986. The cub was born on the birthday of incumbent Tierpark director Heinrich Dathe and was therefore named Björn-Heinrich. His mother Aika is still living at the Tierpark today and is the oldest female polar bear in the world. Björn-Heinrich died on 30 June 2011 at Palić Zoo, having fathered three offspring.
The last successful polar bear breeding attempt at Tierpark Berlin was when Polly gave birth to Felix on 16 December 1994. Today, Felix lives in Parco Faunistico Zoo Safari Fasano (Italy). He has already fathered four offspring.
To date, a total of seven polar bear cubs have been born at Tierpark Berlin to three different mothers. All but one of the cubs were raised by the mothers, the other was hand-reared.
