Workers at the Detroit Zoo say they're in shock after the death of Anana, a female polar bear killed by a male during an attempt to breed on Monday. The zoo says Anana, a 20-year-old bear who came to the zoo last year, lived with 16-year-old male Nuka for several months last year without incident and they were reintroduced last week, Fox 6 reports. "This was completely unexpected and the Detroit Zoo staff is devastated by the loss of Anana in this sudden and tragic event," Scott Carter, the zoo's chief life sciences officer, said in a statement. Nuka has been at the zoo since 2011 and "has lived with, and bred with, several other female bears without showing harmful behavior," the zoo said.
"I wish we understood what happened yesterday with the polar bears," Carter tells WDIV. “We don’t understand exactly what happened that caused the conflict that resulted in her death. We are trying to learn as much as we can." He says Nuka, who fathered twin cubs with the zoo's other female, had lived with Anana problem-free until Monday. "When bears and other large carnivores breed, it is sometimes described in nature as an aggressive encounter," he says. "It usually involves physical control of the female by the male, which usually includes him holding her by the back of her neck." The zoo says it hasn't dealt with one animal killing another since a 1988 incident that also involved polar bears. (Read more polar bear stories.)