One-third of the National Zoo’s flamingo flock was slaughtered by a native red fox that managed to get into the birds’ enclosure through a small hole in the fence.

The carnage was discovered by the zoo’s bird curator at about 6:30 on Monday morning. While conducting her morning rounds, the curator spotted the fox slipping out of the flamingo habitat and running into the woods. Upon entering the habitat, the curator saw the more than two dozen dead American flamingos, along with three injured flamingos, and one dead northern pintail duck.

The remaining flamingos and ducks were moved indoors.

“Something like this has just — it’s never occurred before,” says Brandie Smith, director of the Smithsonian’s National Zoo.

It’s not surprising a fox would be found roaming the zoo grounds — 163 wooded acres nestled within Rock Creek Park. But the animal habitats are well fenced and frequently inspected, Smith says.

“We do know that the zoo is a hospitable place for all wildlife and we spend a lot of time ensuring that our collection is safe from any local predators,” Smith says.

Zoo officials are still investigating the incident, but believe the fox was able to make a “softball-sized” hole in the heavy-duty metal mesh that surrounds the enclosure. Exhibits are inspected multiple times a day, Smith says. The last time the flamingo habitat had been inspected was at 2:30 p.m. on Sunday, and there was no hole or any other area of concern.

In addition to the metal mesh, which is used by many accredited zoos, Smith says, the flamingo enclosure also has fencing underground, to prevent predators from digging their way in.

The zoo is now fortifying the flamingo habitat, as well as other bird enclosures, to prevent future fox incursions.

“Now that we have one predator that has learned how to get through, we are double-meshing all of our enclosures, and we are also adding additional hot wire to serve as a deterrent,” says Smith.

The flamingo habitat — and entire bird house at the zoo — has been closed to the public since Jan. 2017, undergoing a major renovation. It’s slated to reopen later this year. The flamingos inhabit a 9,750-sq. ft. outdoor area complete with a heated pool and barn.

Smith says there is still no decision on whether more flamingos will be added to the flock. The Smithsonian, she says, works with a zoos across the country on species survival program, aimed at maximizing genetic diversity in flamingo populations, and will make decisions about the flock sized based on recommendations from that program.

There are six different species of flamingos in the world. American flamingos, also known as Caribbean flamingos, can be found throughout the Caribbean Islands and on the coast of South America, and are thought to have historically lived as far north as Florida. With an estimated population of 260,000 to 330,000 birds, the American flamingo is not considered endangered, though its habitat in coastal wetlands and marshes is at risk.