Bye,bye, dear Knut!
Knut was born in Berlin Zoo in December 2006. Rejected by his mother, he was put in an incubator and brought up by humans.
His abandonment, cute looks and close relationship with the charismatic zookeeper Thomas Doerflein, turned him into a huge star. He became an environmental symbol, acting as a mascot for the German government's campaign against climate change and being superimposed into a photograph with Leonardo DiCaprio for Vanity Fair's Green Issue in May 2007.
But news of his premature death at the weekend has spurred on those who question both the way Knut was treated and the very fact polar bears are in zoos at all.
While polar bears can live to 30 years old, Knut was only four years and three months when he died. The cause of death has yet to be ascertained but already there have been accusations from animal rights groups.
Knut's life:
2006: Born at Berlin zoo to 20-year-old mother Tosca
Rejected by mother and hand-reared by keeper Thomas Doerflein
March 2007: Debate about whether Knut should have been killed intensifies public affection
2008: Doerflein dies of heart attack, aged 44
2011: Knut dies
Knut generated huge interest around the world
The death of Knut, the world's most famous polar bear, has reopened the debate on the ethical minefield of man's relationship with wild animals. So should polar bears be kept in zoos? asks Tom de Castella.
Some have suggested Knut had behavioural problems
