Zoo Director Steve McCusker says blood tests revealed 59-year-old Boo suffered from lymphoma. For the last month she had been listless, wouldn't eat and lacked mobility. She was put down Sunday.
Boo had performed in circus acts and then was privately owned in East Texas before moving to the zoo about three years ago.
The life expectancy for female Asian elephants in captivity is about 47 years.
Lucky, the zoo's other elephant, is in her 50s.
McCusker says Boo weighed about four tons, was happy to follow instruction and known for her easy-going nature.
He says it's not clear Monday whether the zoo will replace Boo or pursue other options.
Take ABC13 with you!
Download our free apps for iPhone, iPad, Android and Blackberry devices