With computer animation putting trained chimps out of business, concern is growing about what to do with California’s large population of “retired” animal stars.

But for Ollie and Buddy, it is already too late.

The chimp brothers have been shot dead after going berserk and severely injuring two visitors to their animal sanctuary — an old folk’s home for non-human actors.

Ollie and Buddy, both 11 years old, were born and raised in captivity at Bob Dunn’s Animal Services, one of Hollywood’s most famous suppliers of animals and trainers for films, photo-shoots and advertisements.

Although chimps do not usually get movie credits, it is thought that the brothers have made countless Tinseltown appearances. At Dunn’s, their colleagues included Bubbles, the chimp once owned by Michael Jackson.

Yet, like so many star-struck chimps, they found themselves washed up and out of work at the Animal Haven Ranch outside Los Angeles.

Somehow, they escaped from their cages and attacked a visiting couple, James and La Donna Davis.

Mr Davis, 62, is now unconscious in hospital having lost fingers from both hands, an eye, part of his nose, cheek, lips and buttocks, as well as suffering a mangled foot and genitals.

The couple had been visiting their former pet chimp, Moe, for his 39th birthday.

California’s Fish and Game Department is investigating the incident and has put the ranch’s licence renewal on hold.

Like some actors, chimps are useful to directors in their early lives, but become a liability when they get older. Yet chimps can live until they are in their fifties, creating the problem of where to keep them.

“By around 7 or 8, they start changing,” Steve Earl Martin, an animal trainer and owner of Steve Martin’s Working Wildlife, told the Los Angeles Times. “That’s just the way they are. It’s part of their mindsets.”

Chimps have long been the most popular animals in Hollywood because of their ability to look like human beings and smile or perform tricks. Lately, however, chimp trainers have found it harder to get work, as Hollywood studios use computer animation instead of live animals.

In Eddie Murphy’s remake of Dr Dolittle, for example, the chimps were virtual. “With computers and animatronics and such, there’s not as much demand for chimps and live animals any more,” Mr Martin said.

Endla Burrows, director of Jim Henson’s Creature Shop in Los Angeles, says that film-makers prefer to use computer animation because it costs thousands of dollars per minute to shoot a movie, and chimps often fail to perform on cue every time.

Animal rights activists have long campaigned against using chimps for entertainment.

Sarah Baeckler, a primatologist working for the Chimpanzee Collaboratory, says that she saw baby chimps being kicked in the face, punched in the head and struck with broom handles while being trained to perform for shows.

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