Everything had been going so well, staff at the Jerusalem Biblical Zoo claim. Hana, a rare Sumatran tiger, had given birth to three cubs on Nov. 17, and though one hadn't made it long past the birth, the other two seemed to be thriving and bonding with their mother, the Times of Israel reports.

That's why zookeepers were horrified to find the 5-week-old cubs were missing on Friday; they determined that Hana had killed and eaten them. "We discovered they had been killed when we went to weigh them," Nili Avni-Magen, the zoo's chief vet, tells AFP.

Although the Times notes that both wild tigers and those in captivity will eat their young if they're stressed, hungry, or looking to mate, the tragedy was unexpected.

"This was a complete surprise," Avni-Magen tells Haaretz. "We truly thought we were beyond this and that she was on the right path." And a tragedy it is, since there are believed to be fewer than 400 of the critically endangered tigers left in the wild in Sumatra, the World Wildlife Fund notes.

Various conservation programs have enjoyed success at upping the tigers' population: Around 261 of these tigers now exist in zoos thanks to captive-breeding programs, up from 180 in 2008, AFP reports; 32 were born just this year in captivity.

The Jerusalem Biblical Zoo, which showcases animals featured in the Hebrew Bible, has an especially impressive mating record in terms of endangered species, per AFP. Although Avni-Magen says the news "is disappointing and very, very sad," the zoo "will learn the lessons. It could be that this is connected to the behavior of the male." (Read how a med student saved this tiger cub's life.)

This article originally appeared on Newser: Rare Tiger Devours Own Cubs at Zoo

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