The parent company of Ringling Bros. and Barnum & Baily Circus has argued that chaining the elephants during transport is necessary and legal.
Steve Payne, a spokesman for Feld Entertainment Inc., said the elephants were restrained "for their own safety" in accordance with federal guidelines. He compared the restraints to a seatbelt and said the box cars are monitored by circus staff.
But the plaintiffs' lead attorney, Katherine Meyer, said some of the elephants are spending more than half their lives in chains.
"It's not fair. It's not humane, what kind of life these animals have to live in order to give a 12-minute performance," Meyer said.
As for the long hours of chaining, Payne said such durations may have occurred in "extreme instances," but he described Wednesday's legal request as an exaggeration.
"The elephants spend the majority of their waking hours socializing, exercising -- untethered," he said.
In requesting the injunction, the animal welfare groups cited statements from elephant experts asserting that prolonged chaining is harmful in ways that violate the Endangered Species Act. They also cited testimony from former circus employees contending that the elephants were tightly chained by one front and one hind leg for long periods in a manner that prevented them from turning in place.
"The public should be outraged at the amount of time these animals are forced to be shackled and confined," said Lisa Weisberg, senior vice president of government affairs for the American Society for the Prevention of Cruelty to Animals.
The ASPCA is a plaintiff in the long-running lawsuit, along with the Animal Welfare Institute, the Fund for Animals and the Animal Protection Institute.
The lawsuit, alleging multiple violations of the Endangered Species Act, was filed in 2000 and has moved slowly as the two sides battle over many issues, including access to circus veterinary documents and in-house videos.
Meyer said the judge handling case is expected to hold a hearing on the injunction request within 20 days. There is still no date set for the start of the actual trial.
Along with the complaints about chaining, the lawsuit alleges that the circus is violating the Endangered Species Act by abusively training and disciplining elephants with sharp implements such as bull hooks.
Ringling has defended the use of bull hooks as long-accepted tools to control elephants humanely. It says elephants are chained in place at night to keep them from foraging their companions' food, and during train rides to prevent sudden weight shifts that might derail the freight car.
Overall, Ringling has 54 elephants -- 14 of them currently on tour and the others at a conservation center in Florida. The animal groups said even elephants at the center are sometimes chained, but for now they are under court orders not to elaborate.
The plaintiffs hope the lawsuit pressures Ringling to stop using elephants in its shows. Meyer said many circus-goers have come to appreciate animal-free circuses.
However, Payne said Ringling's own audience surveys indicate the elephants are a favorite attraction, and the company is committed to keeping them in the cast.
"They've been the symbol of the circus for 138 years," Payne said.
Payne noted that the American Veterinary Medical Association issued new guidelines last month on the treatment and handling of elephants. It endorsed the use of restraints in certain circumstances, for example during medical treatment or when the elephants might get into fights.
But the association stressed that the restraints "should only be used for the shortest time required for such management purposes."