Lion believed to be oldest in U.S. euthanized

PHILADELPHIA -- An African lion believed to be the oldest held in an American zoo has been euthanized.The Philadelphia Zoo says its 25-year-old big cat named Zenda recently experienced a severe decline in mobility and behavior. She was euthanized Thursday.Zoo officials say Zenda was a popular and much-loved animal. In announcing her death Friday, the zoo noted that lions in zoos typically live about 17 years.Zenda was born at the Johannesburg Zoo in South Africa in 1991. She arrived in Philadelp