Lifestyle Pets Polar Bear Killed During Mating Attempt at Detroit Zoo: 'This Was Completely Unexpected' The 20-year-old female bear was killed by a 16-year-old male bear while he was attempting to breed with her By Georgia Slater Georgia Slater Twitter Georgia Slater is a writer/reporter on the Parents team at PEOPLE. People Editorial Guidelines Published on February 9, 2021 01:38 PM Share Tweet Pin Email Photo: Detroit zoo/ facebook The Detroit Zoo is mourning the death of one of its female polar bears, who died this week during a mating attempt with another bear. On Monday, the Michigan zoo announced that Anana, a 20-year-old female bear, died when 16-year-old male Nuka was "attempting to breed her," according to a press release. Anana came to the Detroit Zoo in January 2020 and was first introduced to Nuka at the end of March. The two bears lived together without incident in 2020, Scott Carter, the Detroit Zoological Society's chief life sciences officer, said in the release. Detroit Zoo Welcomes Polar Bear Cubs for the First Time in Almost 20 Years "This was completely unexpected and the Detroit Zoo staff is devastated by the loss of Anana in this sudden and tragic event," Carter said. As part of the Association of Zoos & Aquariums (AZA) Polar Bear Species Survival Plan, Nuka and Anana were re-introduced last week after being apart for several months. Never miss a story — sign up for PEOPLE's free weekly newsletter to get the biggest news of the week delivered to your inbox every Friday. According to the release, the plan is a "cooperative population management and conservation program that helps ensure the sustainability of healthy captive animal populations." Zoo Miami's Toshi, North America's Oldest Eastern Black Rhino, Euthanized at Age 44 The program is critical to sustaining the endangered polar bear species and recently led to the birth of twin cubs at the Detroit Zoo last November. There are around 55 polar bears in 25 AZA-accredited zoos and aquariums, the release stated. The Detroit Zoo also houses an adult polar bear named Suka, who lives in a private maternity den with one of her cubs. The last time the Detroit Zoo experienced the killing of one animal by another was in 1988. The incident also involved polar bears.