Three lionesses and a lion in the Baghdad zoo escaped from their enclosures at the weekend and were shot dead by US troops.
The lions, which hadn't been fed for days, clawed their way out of their pen through a crumbling wall and two of them charged at American soldiers, said Sergeant Matthew Oliver of the 3rd Infantry Division.
"We had to take them down," he said.
The zoo was home to seven lions and two tigers, as well as hundreds of other animals, nearly all of which were stolen or let loose by looters in the aftermath of the US invasion of the Iraqi capital.
Only the big cats were left untouched, apparently too fearsome for the robbers.
"The zookeeper came the next day and he was pretty cut up, but I think he understood," said Oliver.
The surviving animals, which went unfed for more than 10 days in the confusion that followed the collapse of Saddam Hussein's rule, now have regular meals thanks to a donation of meat from Kuwait.
Mandor the Siberian tiger, the personal property of Saddam's eldest son Uday, looked plumper and healthier than he did last week, while Sudqa the lioness appeared contented in her cage.
US soldiers and four armoured personnel carriers protect the zoo, and Oliver said zoo staff came daily to feed and care for the remaining animals.
Two brown bears, released from their cages by looters, wandered back to the zoo at the weekend and have been nicknamed Boo Boo and Alfred by the soldiers.
"Boo Boo is half blind and was damn near half dead when she came back," said Oliver, trying to attract the mangy bear's attention by poking a carrot through the bars of her cage.
"Come here, baby, don't you want your ears scratched?"
Oliver said Baghdad residents had also returned two hybrid dogs to the zoo, but otherwise the compound was a sad, desolate place.
The Kuwait government, the Kuwait Zoo and a number of private organisations have offered to provide long-term support for the Baghdad zoo.