It's very hard to raise a baby polar bear

BERLIN (Reuters) - Berlin Zoo rallied to the defense of Knut, a three-month-old polar bear cub, Tuesday, rejecting demands that the animal be allowed to die after being abandoned by its mother.

The fate of "cuddly Knut" has gripped the German capital since his birth in December. Rejected by his mother Tosca, the cub was adopted by a zookeeper who moved into the animal's enclosure to care for him round the clock.

Some animal rights campaigners think this will humanize the bear too much and want the zoo to stop saving young animals.

"Hand-rearing a polar bear is not appropriate and is a serious violation of animal rights," Bild newspaper quoted animal rights campaigner Frank Albrecht as saying.

In fact, the cub should have been killed," he added.

Berlin Zoo said the animal would not be put down or left to fend for itself: "That's complete nonsense," a spokesman said.

Knut has become an unofficial Berlin city mascot and has even had his picture taken by photographer Annie Leibovitz as part of a new climate change campaign.

Knut's mother Tosca -- formerly a performing animal in an East German zoo -- rejected Knut and his twin brother shortly after their birth. The twin died but Knut was "adopted" by zookeeper Thomas Doerflein.

The polar bear is bottle-fed, washed and cuddled by his adoptive father, who moved in to the zoo to sleep in a bed by the bears crate. Newspapers report that Doerflein also plays him Elvis songs on the guitar and gave him Christmas presents.