Omaha zoo euthanizes white rhino that arrived in 1999

The Omaha zoo has euthanized one of its white rhinos

OMAHA, Neb. -- The Omaha zoo has euthanized one of its white rhinos.

Officials at Henry Doorly Zoo and Aquarium said Tuesday that the 21-year-old rhino, Marina, was euthanized Monday after surgeons discovered an inoperable colonic obstruction. She was being treated for symptoms similar to colic when staffers noticed that she appeared lethargic.

The 4,000-pound (1,814.4-kilogram) beast arrived at the zoo in 1999. Her death leaves the zoo with another female and a male.

White rhinos are listed as near threatened by the International Union for Conservation of Nature's Red List. In the wild, most white rhinos live in South Africa.