The University of California, Davis, Police Department is investigating the circumstances surrounding the disappearance of a healthy rhesus macaque monkey from the campus's California National Primate Research Center.

The nearly 2-year-old female monkey was reported missing Feb. 13 by two animal handlers who said the animal darted out of its indoor cage during routine cleaning. The tan and gray monkey, which stands about 20 inches high, weighs 4.4 pounds and bears an identifying tattoo. It is valued at approximately $5,000. It was part of the center's disease-free group of animals, and was intended to become part of the breeding colony.

"We are assisting the primate center in expanding the scope of its own investigation," said UC Davis Police Chief Calvin Handy. "We're evaluating all the possibilities."

The primate center houses 4,279 monkeys in a combination of indoor and outdoor facilities. Every year three or four monkeys manage to get out of their outdoor enclosures and are quickly recovered without leaving the premises. Incidents of an indoor animal leaving an enclosure are rare, last occurring some 30 years ago with one animal that was immediately recovered. Security measures were increased at that time.

In this case, the primate center's buildings have been thoroughly searched and food-baited humane traps were set out to lure the animal. Center officials are confident that the animal had not left the grounds on its own, because electronic sensors that monitor movement of any animals over the perimeter fence had not been activated.

To make sure the monkey had not entered the center's sewer system, the piping of that system was explored with fiber-optic cameras.

"Monkeys stay close to their social groups and it is an unusual situation to have an animal unaccounted for," said center director Dallas Hyde. "We have spent days searching and have no evidence that the animal has escaped the premises on its own, or that it is trapped in any part of the facility. Because of that we have asked police to help us investigate the possibility that it was illegally removed from the center."

Located on County Road 98, at the end of Hutchison Drive, the primate facility is one of eight regional primate centers supported by the National Institutes of Health to conduct research in selected areas related to human health. To support its research program, the center maintains a large primate-breeding program.

The center also provides monkeys, mostly rhesus macaques, to research programs at seven UC campuses, as well as other research institutions nationwide. These programs include studies of cancer, asthma, AIDS, osteoporosis, neurodegenerative diseases, and infant development and nutrition.

Anyone with information about the monkey should contact the UC Davis Police Department at (530) 752-1230 or the primate center at (530) 752-0447.