WASHINGTON -- A 40-year-old Asian elephant that was the subject of criticism from an animal rights group was euthanized Wednesday morning at the National Zoo.

Zoo officials said Toni had a long history of arthritis resulting from a leg injury she received before joining the National Zoo in 1989. Officials said the elephant's condition worsened last summer and, based on her recent rapid decline in her condition and quality of life, the decision was made to euthanize her.

An animal rights group demanded last week that Toni be moved to an animal sanctuary, claiming that the National Zoo was mistreating her. Members of the group "Friends of Toni" said the elephant was being crippled in captivity.

Zoo officials said Toni responded well to medical treatment for her arthritis last fall, but she continued to lose weight and muscle mass.

A pathology report may not be completed for several months, according to the zoo.

There is also a 60-year-old elephant living in the elephant house. Ambika the elephant has suffered no ill effects from the rubberized floor in the elephant yard. The asian elephant is a dwindling creature. It could become extinct in our lifetime if it is not saved.

The zoo defends the practice of putting these animals in exhibits to stimulate public interest in their survival. It plans to artificially inseminate another elephant, Shanthi, this spring to add a second baby to the herd.

Officials from the National Zoo admit the elephant house needs improvement. The zoo will unveil a blueprint for a new facility in two to three weeks that will make use of its 3,000 acres in Front Royal as a place for the elephants to roam.