Bubbles, now 27, was not provided for in Michael's will and the sanctuary bosses raise the annual 13,000-pound bill to care for him, reported Daily Mirror.
As Michael's loyal sidekick, he was once the most pampered and powerful primate in pop.
He travelled first class around the globe without a hint of hassle and even joined Michael on his 1987 Bad tour of Japan.
When he wasn't mimicking the King of Pop's trademark Moonwalk, he enjoyed a glitzy existence, going to star-studded premieres, gigs and album signings.
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A spokesman said that Michael's sister La Toya had paid a visit there, as part of a documentary she was filming with Animal Planet, about two years ago but that was the only visit they have had from a member of the Jackson family.
Michael originally rescued two-year-old Bubbles from a Texas medical lab and had him raised by an animal trainer before officially adopting him in 1983.
But, after the birth of Michael's son Prince Michael Jr, Bubbles was deemed too dangerous to be around children and was sent off to live with Hollywood animal trainer Bob Dunn.
Workers at the sanctuary said that Bubbles is well-cared for and happily passes his days eating sweet potatoes, watching TV and listening to music.