(Adds details about decision)

By Colleen Jenkins

March 5 (Reuters) - Ringling Bros. and Barnum & Bailey Circus will eliminate its elephant acts - long an integral part of the spectacle billed as "The Greatest Show on Earth" - by 2018 amid criticism by animal welfare activists, the circus' parent company said on Thursday.

Feld Entertainment said the 13 Asian elephants used in its traveling shows will live at the company's 200-acre (81- hectare) Center for Elephant Conservation in central Florida after they are retired over the next three years.

The animals represent a key symbol of the circus and have been part of its shows for more than a century. The company said the move was in response to changes in consumer preferences and the legislative landscape, and would allow it to focus on its conservation efforts for the endangered species.

"This decision was not easy, but it is in the best interest of our company, our elephants and our customers," Kenneth Feld, chairman and CEO of Feld Entertainment, said in a statement.

The circus has been targeted by animal welfare groups who accused it of mistreating the elephants. Activists often appear outside show venues, handing out fliers protesting the use of elephants and showing pictures of animals they say are abused.

After Feld Entertainment fired back with a lawsuit claiming malicious prosecution, more than a dozen animal welfare groups agreed in 2012 and 2014 to pay settlements totaling about $25 million to end 14 years of litigation.

Ingrid Newkirk, president of People for the Ethical Treatment of Animals (PETA), a longtime critic of Ringling Bros' treatment of elephants, said on Thursday the circus should not wait to phase out elephants from its performances.

"If the decision is serious, then the circus needs to do it NOW," Newkirk said in a statement.

Feld Entertainment, based in Ellenton, Florida, has 41 Asian elephants in its herd, the largest in North America, said company spokesman Stephen Payne. He said relocating the show elephants to the center will take time due to construction and staffing considerations.

The company has decided to spend resources on its elephant breeding program rather than continue to fight laws put in place by some of the cities it tours in that restrict how the circus handles the animals, Payne said.

"We're not in the business of fighting city hall," he said.

The company said it will still showcase tigers, lions, horses, dogs and camels in its acts. (Additional reporting by Barbara Goldberg; Editing by Frank McGurty and Bill Trott)