On its farewell tour, "The Greatest Show on Earth" is still causing a stir.

As Ringling Bros. and Barnum & Bailey circus began its nine-day stop at the Barclays Center in Brooklyn last week, animal rights activists began their own sustained protest outside.

Called the Animal’s Battalion, the grassroots group has demonstrated at nearly every performance the circus has put on at the Barclays Center since the space opened in 2013.

It is again mustering forces to protest the circus’ final 15 performances at the Brooklyn arena, which end on Friday.

Last month, the 146-year-old circus said it would fold up its tent forever, citing low attendance, high operating costs and the impact from pulling the elephant act from the show last year. After a multi-state tour, it will hold its final performance on May 21, at the Nassau Veterans Memorial Coliseum in Uniondale, N.Y.

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Despite Ringling's stated intention to close, the animal activists have not gone away.

For the Brooklyn shows, protesters include PETA, Compassionate Works International and Long Island Orchestrating for Nature (LION). Those members will join The Animal’s Battalion and its founder, Roberto Bonelli.

“Ringing is coming to an end, but our work is not because animal abuse continues,” Bonelli told Metro. “There are other circuses,” he said, citing Cinco Hermanos Vazquez and UniversSoul Circus, which still use animals in their shows.

The fanfare Ringling Bros.’ last days has stirred is also a good opportunity to educate the public, Bonelli said.

P.T. Barnum introduced animal acts to the circus

It dates back to 1871, but the circus really expanded under showman P.T. Barnum, who established the use of exotic animals in his act at the original Madison Square Garden, and acquired the African elephant, “Jumbo,” in 1882. He continued to highlight animals as spectacle, and once paraded exotic creatures, including 21 elephants and 17 camels, across the newly built Brooklyn Bridge — to demonstrate its soundness — in 1884.

The current version of Ringling Bros. and Barnum & Bailey formed in 1919. That was when the Wisconsin-based Ringling Brothers’ World's Greatest Show merged with Barnum & Bailey’s Greatest Show on Earth, 28 years after Barnum’s death.

While Ringling Bros. retired elephants from the stage last year (they went to the circus’ own Center for Elephant Conservation in Florida), it still uses lions and tigers. Bonelli said those animals have no business being in a circus, and should either be released to their natural environment or kept in sanctuaries.

Despite the objections of animal advocates, the circus has its legions of fans, and P.T. Barnum remains a symbol of a bold American entrepreneur.

Dick Zigun counts himself an admirer, and considers himself something of a Barnum “scholar.”

Zigun, who founded the Coney Island Mermaid Parade and the Coney Island Circus Sideshow, said Barnum “literally invented popular culture in a growing New York City.” Zigun, who hails from Barnum's hometown of Bridgeport, Connecticut, added, “the whole style of advertisement and promotion began with Barnum’s genius.”

Zigun said he will mourn the loss of Ringling, and said that the decision to retire the elephants was a sign that Feld Entertainment, which acquired the circus in 1967, was ready to evolve.

But as long as a circus uses animals in their performances, it will always be a symbol of the past, Bonellii said.

“A lion should not be going to Brooklyn, or stuck in a cage going to Newark [another planned stop] in 30 degrees,” Bonelli said. “Ethics is not difficult. It’s common sense. Nobody will tell you it’s a good idea to take them from Africa in tiny crates to perform tricks.”

As for the fate of the circus' remaining tigers, camels, goats and horses, Ringling Bros. told Metro in a statement that "the company is diligently working to find homes for all the animals that are on the circus. Our commitment to their care and well-being continues beyond the last performance."