Seven-year-old Norman Bates, the son of Hitchcock and Morticia, “was renowned throughout the center for his feistiness and intelligence.” (Courtesy of Duke Lemur Center)

Four beloved lemurs, all endangered, have died at the Duke Lemur Center since Tuesday in the care of “two of the world’s foremost lemur veterinarians,” the university announced.

The deaths, which occurred suddenly in emergency care, have been blamed on “a mysterious affliction” that officials are desperately struggling to unravel, the center said in a news release.

All four of the dead animals — two males and two females ranging in age from 7 to 28 years — belonged to a species of lemur called aye-ayes, which are the world’s largest nocturnal primates, according to the Duke Lemur Center.

Greg Dye, the center’s operations director, called the deaths “devastating.”

“The people here live and breathe lemurs,” he said. “Their passion is just boundless. This has been a tragic day for us.”

Lemurs are the most endangered group of mammals on the planet. The Duke center, in North Carolina, has the largest collection of lemurs outside of Madagascar, the island nation off the southeast coast of Africa from which the endangered primates originate.

There are fewer than 50 aye-ayes in captivity in the entire world, Dye said, calling the loss of four animals a “big blow” to the lemur center’s conservation and breeding programs.

“We had 13, and now we have nine,” Andrea Katz, the lemur center’s animal curator, said in a statement. “This is the most significant loss we’ve ever had and is a terrible blow to our breeding program. This is a significant percentage of the aye-ayes in the U.S. at this time.”

According to the Duke Lemur Center, aye-ayes are considered unique among 100 or so species of lemurs.

“They are cat-sized, gray-black creatures with enormous floppy ears, large round eyes and bushy black tails,” the Duke news release explains. “They are active at night, hunting insects in tree trunks using teeth like a beaver and an extraordinarily thin and flexible middle finger that extracts their prey. They are also believed to be the most intelligent members of the lemur family, which are distant primate cousins to humans.”

Dye said no other animals had been affected by the unknown illness, but the center’s staff is rushing to determine the cause of the deaths while closely monitoring the other 250 lemurs at the center “for signs of distress.”

“We’ve looked at ambient air and animals’ diets and water supply and any enrichment that was used in the animals’ rooms,” he said, noting that investigators will examine the animals’ food and toys, as well. “We’re going to start putting together a puzzle and try and pinpoint what happened here.”

In the meantime, Dye said, investigators will have to wait to solve the puzzle entirely. Investigators have numerous tests in progress, he said, but most results won’t be ready for another two weeks. The earliest results are expected to arrive in the next five days, he said.

Dye said the stricken animals deteriorated quickly after a technician noticed the aye-ayes behaving lethargically around 3 p.m. Tuesday.

Minutes later, the animals were transported to the center’s emergency room. One of the animals died within 20 minutes of arriving at the emergency facility.

That night, three more aye-ayes deteriorated and died in the same fashion.

Only an hour before the first animal became sick, the news release notes, video cameras captured the lemurs behaving normally.

Duke veterinarian Bobby Schopler said the quick nature of the deaths made it unlikely that the animals succumbed to an infectious agent.

“There is probably a single cause,” Schopler said.

Aye-ayes were thought to be extinct but were rediscovered in 1961, according to the World Wildlife Fund.

The species has faced multiple threats, including an old superstition among Madagascar’s Malagasy people, who believe aye-ayes should be killed on sight.

“The aye-aye remains an endangered species not only because its habitat is being destroyed, but also due to native superstition,” the WWF notes. “Ancient Malagasy legend said that the Aye-aye was a symbol of death, with some believing its mere appearance predicts the death of a villager.”

“The dozens of diverse lemur species on Madagascar are a motley crew,” the American Museum of Natural History notes. “Still, none look and act quite like the aye-aye. In fact, this lemur is considered one of the world’s strangest animals altogether.”

According to the museum’s chief conservation scientist, Eleanor J. Sterling, a leading aye-aye expert: “The aye-aye is a unique animal. It’s the only member of its family, which means it has no very close relatives. It’s a primate — but an unusual one. It is the exception to just about every rule about what makes an animal a member of the order of primates. In the course of my studies, I kept reading and hearing, ‘All primates do this or that … except the aye-aye.’

“People say that the aye-aye is made up of the spare parts of other animals: It has huge ears like a bat; a big, long foxlike tail; and continually growing teeth like rodents, something you never see in the primate world. And it has claws. One of the things that distinguishes primates from other animals is that they have nails, not claws, but the aye-aye has claws.”

The World Wildlife Fund has observed that aye-ayes bear a resemblance to a certain character from the Harry Potter series: “If you compare a picture of an Aye Aye with that of house elf Dobby, you could be forgiven for thinking they were born of the same mother.”

Researchers at Duke have embraced the singular species, noting that “the aye-aye is so emblematic to the Duke Lemur Center that it is featured in the center’s logo.”

The university’s news release notes that the lemur center “pioneered the breeding of aye-ayes in captivity, and many animals born in Durham are now housed around the country in zoos and conservation centers. Three of the four that died were born at Duke.”

Said Katz, the center’s animal curator: “What happened here is important for all of the aye-aye breeding colonies in the world. I hope we can learn something that will prevent this from ever happening again.”

Lemur Center Director Anne Yoder said the “tragedy” left the staff “devastated.”

“This kind of loss is one of the awful consequences of this great responsibility we carry,” she said.

This post has been updated.

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