Knut and his unnamed brother were born at the Berlin Zoo on 5 December 2006. Their mother Tosca rejected her cubs for unknown reasons, abandoning them on a rock in the polar bear enclosure. Zoo keepers rescued the cubs, but Knut's brother died of an infection four days later. Knut was the first polar bear to have been born and survive in the Berlin Zoo in over thirty years. With an starting weight of 80g (2.8oz), he spent the first 44 days of his life in an incubator. Knut's need for around-the-clock care required that his zoo keeper not only sleep on a mattress next to Knut's sleeping crate at night, but also play with, bathe, and feed the cub daily.
(source: wikipedia)