Portland, Ore. -- The Oregon Zoo is mourning the loss of one of its tigers today.
15-year-old female Amur tiger named Nicole died Monday after what animal care staff believes was a seizure.
Oregon Zoo officials conducted a necropsy and found hemorrhaging and other irregularities but the cause of death is still unknown.
An Amur tiger's life expectancy is 16 years for males and just over 14 years for females.
Nicole was born on Halloween and moved to the Oregon Zoo nearly 14 years ago.
(Photo courtesy of: http://www.oregonzoo.org )