Officials at Lansing's Potter Park Zoo are investigating the death of a four-year-old bongo antelope.
Zoo director Gerald Brady says the bongo, named Bea, was found lying down and unresponsive in her stall on Tuesday morning.
He says the cause of death won't be determined until various tissue, blood, and urinalysis tests are reviewed.
A Potter Park veterinarian said Bea had seemed healthy, but she added that wild animals have survival mechanisms that often mask signs of disease.
Bea had been scheduled to be artificially inseminated on Tuesday.
Bongos are large, horned chestnut-red antelopes. They're elusive creatures that normally live on the edges of rain forests in central Africa.