The Columbus Zoo and Aquarium says four rare Amur tiger cubs have been born at the zoo, the second-such litter in a year. The zoo says the cubs are being cared for by their mother and the family is being monitored by an animal care team using a camera in the tigers' den. The cubs are the second for the mother, 6-year-old Mara, and a 10-year-old male, Foli. Two cubs born in June had to be hand-raised by staff because of concerns about the first-time mother's care and disruptions to the monitoring camera because of a power outage. The Amur tiger, historically known as the Siberian tiger, is the largest of the big cats, with fewer than 500 believed to live in the wild in Russia.