Three monkeys died this week after an incident at the Baton Rouge Zoo in which dogs entered the facility and attacked the primates.
The fatally injured greater spot-nosed guenons were discovered in their exhibit this week, said Sam Winslow, the zoo's assistant director.
"The keepers came in that morning and found the monkeys basically chewed up by some dogs," Winslow said. "They were inside their enclosure still."
Winslow said the guenons, which weighed about 11kgs each, were "pretty aggressive." Officials believe they might have reached out from their cage, prompting the attack.
"So we suspect that the dogs went up to them and the monkeys tried to reach out and grab the dogs, and then got their arms caught by the dogs," he said. A 29-year-old female monkey, a 22-year-old male and 18-year-old male all died of their injuries, the Advocate reported. According to the newspaper, two were dead when they were discovered by the keepers, and one needed to be euthanised.
Officials have reviewed surveillance footage from a nearby concession stand that shows two dogs in the area, according to Winslow.
Winslow said officials have yet to track down the dogs, which appear to be terriers. They did review their perimeter fence in the wake of the attack, to try to figure out how the dogs entered the facility.
"It's hard to blame the dogs for this. It's really the irresponsible pet owners that let their dogs go out at random," Winslow said. "These didn't look like they were starving strays. They were probably someone's house pet. People turn their dogs out at night - they get into trouble, and they cause damage, whether it be with cats, or other dogs, or children, even. So it's really irresponsible pet owners that are to blame for this."
Winslow said officials aren't sure exactly when the attack took place, but the footage captured the dogs in the zoo at around 5am Tuesday (US time).
"All we could find is at one gate, there was a gap that was probably about four to six inches, where two gates come together, and they may have gotten through there," he said. "That's what we supposed anyway, we really can't - don't know for sure. It's a pretty small gap."
The greater spot-nosed guenon is found in Africa, and they are known for their color patterns. The three that were attacked were the only greater spot-nosed guenons housed in the Baton Rouge facility, Winslow said. No other monkeys were injured in the encounter.
"It was surprising for us, because we typically keep all of our smaller animals secured at night, because we have a lot of raccoons and such, that come into our zoo," Winslow said. "So we secure a lot of those animals. So we're surprised at something like that, that an animal that's in an enclosure would be able to be attacked by dogs."
The Advocate notes that this isn't the first fatal dog attack at the Baton Rouge facility. Dogs also killed 17 flamingos in a 2010 incident.