BERLIN (AFP) – An animal rights group has called for Knut the polar bear, who shot to global stardom as a cub in 2007, to be castrated to avoid incest with his cousin.

The three-year-old darling of Berlin Zoo was given a female companion, Giovanna, last year but the German chapter of People for the Ethical Treatment of Animals (PETA) warned against their mating.

The group's zoo expert, Frank Albrecht, noted that Knut and Giovanna, known as Gianna for short, had the same grandfather.

Any offspring would threaten the genetic diversity of the polar bear population in Germany and risk exposing the bear couple to a condition known as "incest depression", he said.