Police are investigating the brazen theft of a beloved squirrel monkey named Banana Sam from the San Francisco Zoo.

The 17-year-old primate was stolen late yesterday, San Francisco police Sergeant Michael Andraychak said. The zoo is offering a 1,000 US dollar reward for Banana Sam's sage return.

"It was apparent someone broke into the zoo and deliberately took the animal, we believe somebody has him," Sgt Andraychak said.

Zoo officials discovered Banana Sam missing when they arrived at work. The monkey is about a foot tall and weighs approximately 2lb.

The zoo said the thieves cut a back perimeter gate and made it to the top of a roof that houses five other primate exhibits. The vandals cut two holes into the mesh of the squirrel monkey exhibit and snatched Banana Sam.

The zoo, which keeps about 20 squirrel monkeys, said it is concerned on many fronts.

First, Banana Sam requires a special diet to survive and is older. Also, while squirrel monkeys are not large animals, they have sharp teeth and will bite if provoked.