By BARBARA RODRIGUEZ, Associated Press

DES MOINES, Iowa (AP) — Pamela and Tom Sellner describe the small zoo they opened in northeastern Iowa nearly 15 years ago as a labor of love that evolved from their respect for animals.

Among the more than 150 creatures at their 6-acre Cricket Hollow Zoo in Manchester are several that one might not expect to find in a Midwestern farming community, including tigers, lions and lemurs.

But the California-based Animal Legal Defense Fund and several Iowa residents are suing the couple, saying their so-called roadside zoo has been mistreating animals for years. The trial, which began Monday in a Cedar Rapids federal court, could provide the first definitive court ruling on how these zoos must care for animals considered endangered.

"It would mean that the roadside zoo owners are on notice," the ALDF's senior attorney, Jessica Blome, told The Associated Press by phone Wednesday. She went on to say, "If they don't treat (endangered) animals well, if they don't make sure they have proper veterinary care, if they don't make sure that the natural environment is as closely proximate as possible, then the animals have to be taken away and they don't deserve to have them."

Closing arguments are expected Friday. Neither the Sellners nor their attorney, Larry Thorson, responded to phone messages seeking comment.

In court filings and a posting on the zoo's website, the Sellners denied the lawsuit's allegations, saying they love animals and have been unfairly maligned.

"We have personally received hate mail, death threats," Pamela Sellner wrote on the website.

There have been other lawsuits over the treatment of animals by roadside zoos in the U.S., which are estimated to number in the hundreds. They are licensed through the U.S. Department of Agriculture, but animal rights groups say the federal oversight system for these zoos needs an overhaul.

The Iowa lawsuit specifically challenges how the Sellners' zoo cares for its animals protected under the Endangered Species Act — four tigers, three lemurs and three wolves. A similar case in North Carolina is pending, but animal advocates expect the Iowa case to be resolved first, with the judge expected to rule in about a month.

According to the lawsuit, some of the individuals who are suing the Sellners began visiting their zoo in 2012 and were dismayed by the animals' living conditions. They said that during multiple visits, they saw the animals being kept in cramped and feces-filled cages. Some animals had no access to water, and the water that was available was visibly dirty. Other animals, including lemurs, were kept in isolation despite their needs as social creatures. In one instance, an emaciated female lion with flies crawling on her started throwing up, the lawsuit contends.

In its court filings, the ALDF says five tigers have died at the zoo since 2013. None of the animals' bodies were lab-tested and their deaths were attributed to various ailments or old age. The group also says five lemurs died at the zoo from 2006 through 2011.

There have been multiple violations against the zoo over the years, though the Sellners say in legal filings they have been resolved. Earlier this year, the USDA temporarily suspended the facility's license.

Tanya Espinosa, a spokeswoman for the agency's Animal and Plant Health Inspection Service division, said the USDA has an open investigation into the zoo over its compliance of the Animal Welfare Act, but she would not comment on the details. There are several possible outcomes from the investigation, including the zoo's license being revoked.

The lawsuit asks that the endangered animals be removed from the property and sent to facilities that could better care for them. Blome said the ALDF has filed a separate lawsuit against the USDA over its renewal of the zoo's exhibitor license despite evidence of its repeated and ongoing violations of the Animal Welfare Act. That case is pending.

Espinosa said the USDA doesn't comment on pending litigation.

Debbie Leahy, manager of captive wildlife protection at the Humane Society of the United States, said people should stop visiting roadside zoos.

"Don't believe the manufactured fairytales about how an animal's being rescued or they're breeding endangered species," she said. "They have to be more discerning about the places they visit that keep captive wildlife."