A Grevy’s zebra grazes at the National Zoo in Washington on Nov. 18, 2013. (Jacquelyn Martin/AP)

The director of the National Zoo said Tuesday that the recent deaths of three animals and a Grévy’s zebra’s attack on a keeper indicate that the zoo’s resources and staff are stretched too thin.

The comments by Dennis Kelly came as the zoo concludes reviews of two internal reports into several serious incidents at its Cheetah Conservation Station within the last year.

One of the worst mistakes was the death of a female red river hog that died of septicemia in the zoo hospital Dec. 17 after she had lost a quarter of her weight in eight weeks, apparently because of improper nutrition.

When the hog, named Holly, was taken to the hospital, she bore cuts and scabs of unknown origin. She weighed 110 pounds when she arrived last year and 79 pounds when she died.

“We lost her,” said zoo spokeswoman Pamela Baker-Masson. “We shouldn’t have.”

Kelly said the lapses are largely the result of stretched resources. “I can’t spread this staff any more thin than it is now,” he said.

The second animal death was that of a pregnant kudu, a type of antelope. It apparently became spooked by something, ran into a paddock wall and broke its neck. The animal arrived at the zoo May 10 and was found dead June 16.

Neither death was announced at the time because the animals were not yet on public display, the zoo said.

The details of those deaths are in a report on conditions at the cheetah station, an exhibit near the Connecticut Avenue entrances to the facility that has cheetahs and other animals. Parts of the report were summarized by a Smithsonian official who spoke on the condition of anonymity because the report was still being reviewed.

The report was sparked by complaints in June from a volunteer who brought a series of concerns to Kelly and the head of animal care, Don Moore, who set up a committee to conduct the probe.

“That process was a good one, and [it] resulted in some things that are making us better,” Kelly said Tuesday.

“We are spread too thin, is the conclusion that I’ve come to,” he said. “Not just that area. It’s really the whole zoo — I dare say the whole Smithsonian . . . as a result of the almost three years now of budget uncertainty and budget cuts.”

“My staff is as good as anybody in the zoological community,” Kelly said. “We’re well-trained. People know what they’re doing. They’re dedicated. For the collection that we have, we’re spreading ourselves too thin at the moment.”

The report, which was completed Sept. 3, also details last spring’s escape of a female non-flying vulture named Natalie, who apparently was able to use a wind gust to soar out of her enclosure.

A “code green” alert for an escaped animal was issued, and the vulture was caught moments later in an adjacent parking lot. The zoo said it now keeps the bird’s flight feathers better clipped.

In a later incident, a red panda escaped from in June by using overhanging tree branches and got some distance away before it was captured.

The report also discloses the case of two Abyssinian ground hornbills who were kept in an inadequately sized indoor holding area for eight months. The zoo said that situation has been rectified.

The third animal death was that of a Dama gazelle, which perished after it apparently ran into the wall of an enclosure after being startled by the zebra attack in an adjoining compound, the zoo has said.

On Nov. 18, Wayne Millner, a veteran zookeeper, was attacked by the Grévy’s zebra after entering the animal’s compound. Zebras are dangerous and can weigh up to 900 pounds.

Millner, who was bitten and kicked, was hospitalized with severe injuries, the zoo has said. He has returned home but not to work.

It was not clear how the zebra came to be in the compound with Millner, but a zoo safety report on that incident is due this week.

The reports contrast with the hoopla and money the zoo has spent on its higher-profile exhibits, such as those containing its wildly popular giant pandas and Asian elephants.

On Dec. 1, the zoo hosted an elaborate ceremony, featuring a video greeting from first lady Michelle Obama, to announce the name of its female giant panda cub, Bao Bao.

The pandas reside in the David M. Rubenstein Family Giant Panda Habitat, named for the local philanthropist who donated $4.5 million to the giant panda research and reproduction program.

And the zoo recently spent $56 million to create its new state-of-the-art Elephant Trails complex, which can accommodate up to 10 Asian elephants and their young.

“We’re not staffing pandas or elephants any more or less with the international standard,” Kelly said.

“I can understand why somebody might think we’re lavishing more money or attention” on such exhibits, he said.

“But that money is private. The actual zookeeping aspect of it is at the proportions that are safe and normal for our profession.”