The theft of a young Callimico goeldii from Cherry Brook Zoo in Saint John isn't just a case of monkey business, say staff.

April, a small marmoset from South America, was stolen from the zoo on Tuesday night after someone appears to have used a hacksaw and kicked a heavy, padlocked door open, said Lynda Collrin, a spokeswoman for Cherry Brook Zoo.

The tiny black monkey is less than a year old and was part of an international breeding program, Collrin said, adding the zoo won't press charges if the animal is returned.

"We will not give a name, just please, please bring this animal back," Collrin said.

The animal is about 30 centimetres talls and weighs less than half a kilogram, Collrin said. It requires special feed and should be with its parents and its siblings, she said.

"It can carry disease … It has upper and lower canine teeth. It can inflict damage and it's terrorized right now," she said.

It would not make a good house pet, she added.