Bob Givens, one of the key members of the animation team that created Bugs Bunny, has died in California aged 99.

Givens died of respiratory failure at a hospital in Burbank on December 14. His daughter Mariana Givens confirmed his death on Facebook.

Givens was one of the last surviving animators from the industry's early years. His career spanned more than 60 years and included work illustrating characters such as Tom and Jerry, Daffy Duck, Alvin and the Chipmunks and Popeye.

But Givens was best known for his work on the cartoon rabbit whose image and signature line "What's up, Doc?" became recognised around the world.

Givens was a rising animator in the 1930s when he played a role in re-imaging Bugs Bunny.

The rabbit with an attitude had evolved through a few animated shorts, but was seen as "too cute" until Givens gave it a makeover, according to the book Hollywood Cartoons: American Animation in Its Golden Age.

He gave the character an oval head and introduced elements such as cheek ruffs and less prominent teeth, the book's author, Michael Barrier, wrote.

Bugs Bunny debuted in A Wild Hare in 1940, an animated short film that included a redesigned Elmer Fudd, the rabbit's co-star and witless nemesis, prepared by Givens.

Givens' first big break was on the animation team for Snow White and the Seven Dwarfs at the Walt Disney Studios. He also worked for Warner Brothers and Hanna- Barbera. He served in the US military in World War II.