The Columbus Zoo and Aquarium in Ohio says it has euthanized a 29-year-old male polar bear after veterinarians determined he had liver cancer with limited treatment options.
The bear euthanized Wednesday, Nanuq fathered five surviving offspring in a species with a low reproductive rate.
Three are cubs born to the zoo's two female polar bears last November. Nanuq also fathered Nora, who moved from Columbus to the Oregon Zoo, and Luna, who remains at the Buffalo Zoo.
Officials say Nanuq was rescued as an orphaned cub in Alaska in 1988 and lived at the Henry Vilas Zoo in Wisconsin. He was moved to Buffalo in 2009 and to Columbus in 2012.
The zoo says Nanuq surpassed the median life expectancy for such a bear by eight years.