Polar bear cubs at Germany's Nuremberg Zoo may be left to die if their mothers reject them, a top zoo official says.
Two female polar bears - Vera and Vilma - gave birth a few weeks ago.
The zoo wants to avoid any repetition of "Knut mania", a popular craze triggered by a hand-reared bear cub at Berlin Zoo last year.
The zoo's deputy head, Helmut Maegdefrau, said instead of helping the cubs, his team would let nature take its course.
They are not disturbing them - and do not know yet how many cubs there are.
The polar bear cub Knut was rejected by its mother last year, but Berlin Zoo decided to hand-rear it - a move which proved enormously popular.
But Mr Maegdefrau, quoted by the German news website Focus, said "we should have faith in nature and accept that sometimes with new mothers things just don't work out".
The zookeepers are keeping their distance from the mothers and their cubs, secluded in a cave.
"If you don't let the mothers practise, they will never learn how to bring up their cubs," Mr Maegdefrau said.
"If we were to go in, we would disturb them and make it more likely that something goes wrong."
Berlin Zoo said it disagreed with Nuremberg's decision.
Since they started hand-rearing Knut, he has become a celebrity - both in Germany and worldwide.