An endangered primate at the Sacramento Zoo died unexpectedly last month.
Jimmy, a 13-year-old golden-bellied mangabey, collapsed Dec. 29; veterinarians were unable to revive him, zoo officials said Thursday.
Little is known about mangabeys, but they are thought to live in a small area in the Democratic Republic of Congo.
The primates are considered endangered because of poaching and habitat loss.
There are 19 golden-bellied mangabeys in North American zoos.