Prosecutors say a 22-year-old Idaho man killed a patas monkey after the primate bit him as he attempted to steal it from a Boise zoo.
Michael J Watkins faces charges of felony burglary and grand theft for allegedly taking the monkey and beating it so severely that it later died.
"He told police he was going to throw the monkey outside the fence," Ada County Deputy Prosecutor Fafa Alidjani said on Wednesday, adding that the monkey bit Watkins, prompting him to use a tree branch to bash it in the head and neck.
If convicted, Watkins faces up to 10 years in prison for the burglary charge and 14 years in prison for the grand theft charge.
Idaho law allows prosecutors to bring a grand theft charge against someone accused of killing livestock or other animals valued at more than \$150.
Ms Alidjani said Watkins entered the zoo on Saturday morning, manipulated a lock to get into the primate enclosure and removed the patas monkey by wrapping it in his jacket.
District Judge Michael Oths denied a request from Watkins' public defender to reduce bail from \$150,000 to \$10,000.
Prosecutors argued bail should not be reduced because Watkins has a history of arrests from drugs and drunken driving, and probation violations.
Watkins's public defender, Gary Reedy, said his client broke into the zoo after a night of grief-fueled drinking.
Mr Reedy said Watkins' aunt had recently died, and Watkins' grandmother had been diagnosed with cancer only days before. So he went into Boise for a night out with friends and family.
"He was taking it very hard," Mr Reedy said. "He became intoxicated."
Watkins' father, Jerry Watkins, has defended his son to the Idaho Statesman, saying he is "not a malicious monkey murderer".
He said it was a drunken prank, that his son was trying to get a picture with the animals.