Packs of stray dogs have been marauding at Indiana zoos, massacring eight exotic birds at the Indianapolis Zoo on Sunday and killing eight fallow deer over a period of three days at a private zoo in Parker City.
At least one of the dogs involved in the attacks was wearing a collar, but so far officials have been unable to determine whether the dogs are housepets on a spree or feral animals.
The killing spree at the Indianapolis Zoo left eight Australian birds dead and devastated zoo staff.
Zoo officials said they believe the birds were killed around 6 a.m. on Sunday, and they had to delay opening the zoo for three hours while they double-checked security at the facility.
The dogs attacked the birds in an exhibit beside the elephant and giraffe exhibit. They wiped out the zoo's entire emu population, and also killed two black swans and three magpie geese.
"There's no question that they were on a spree," zoo President Mike Crowther said Sunday. "The animals in that area were definitely devastated. We're obviously saddened by the loss of these birds. There are a number of staff in tears today."
After examining the perimeter fence for any area that the dogs may have exploited to get into the facility, zoo officials said they believe the dogs were able to get in by squeezing under the main gate.
Officials believe the six dogs entered the zoo while chasing at least one raccoon. The bodies of two raccoons, apparently mauled by dogs, were found outside the zoo and another was found inside, officials said.
"It's a shocking way to lose animals," Paul Grayson, zoo vice president, said of the birds' deaths. "It is a rare instance that a dog pack gets into a zoo."
Zoo employees monitoring surveillance cameras saw the attack as it was going on. They called animal control offiicers and Indianapolis police, but by the time they arrived the damage had already been done.
Four of the dogs -- three described as lab/chow mixes and one said to be a terrier mix, were shot and killed by police, another escaped.
A sixth dog, a male pit bull, was captured and taken to a humane shelter, but because of his aggressive nature, the dog that was caught will likely be euthanized later this week, officials said.
Officials said if they can find out who owned the dogs involved in the attacks, they plan to file charges against them.
By Monday, the zoo had placed wooden boards at the bottom of its entrance gates, closing the gaps. Zoo officials said they plan to improve fencing at the entrance and increase the number of security cameras. The zoo already monitors surveillance 24 hours a day in a control center.
A similar tragedy struck ME's Zoo in Parker City, one of the largest private zoos in the country, where officials said stray dogs killed eight fallow deer over three days.
Two deer were killed Saturday and six were killed Monday, and some of the deer were only a few weeks old, zoo development director Bob Taylor said.
Two dogs suspected of killing the animals were found Tuesday and destroyed, Taylor said. One of those two dogs was wearing a collar, but it didn't give investigators information about an owner, he said.
As at the Indianapolis zoo, officials at ME's said they will press charges if they find the owners of the marauding animals.
Information on how the dogs entered the zoo's deer exhibit wasn't available. The zoo on Tuesday assigned more employees than usual to monitor the perimeter fence around the facility's 7,200 square feet, because they didn't know whether any other dogs were on the loose.
ME's Zoo has more than 200 animals. Parker City is about eight miles east of Muncie.
Zoo officials and animal control officers hope these events help them send a message to all pet owners.
"Spaying and neutering is the single most-important step to stop pet overpopulation, which is what leads to this kind of problem," Indianapolis Animal Care and Control community outreach director Media Wilson said.
ABC News affiliate WRTV-TV in Indianapolis contributed to this report.