Activists are calling for restrictions on who can own exotic animals in the US amid claims that species such as tigers are being mistreated.

More than 5,000 tigers are kept as pets in the US, while only 3,200 remain in the wild globally.

Americans can get permission to keep tigers relatively easily by giving a name, address and a $40 fee.

This allows owners to legally keep a big cat in most US states.

But for many tiger owners the animals soon become too difficult to handle and many animals fall victim to abuse.

Some are bred for profit and starved while kept in cages that are too small.

This happened to Keisha and Zeus, two tigers who were being held at JNK's Call of the Wild Sanctuary in New York.

After years of complaints about the conditions, the US Department of Agriculture shut the zoo down.

Keisha and Zeus were lucky - they were transferred to Big Cat Rescue in Florida.

Zeus now has around 2,000 square feet to roam in. He's fed properly and kept close to Keisha.

Breeding brings cute and profitable tiger cubs. At Dade City Wild Things petting zoo you can pay $200 to swim with a cub.

Ten people a day means a pretty decent sum but the US Department of Agriculture has filed a complaint against the zoo - aimed at this very attraction - accusing it of mishandling the animals.

Head trainer Randy Stearns denies he is exploiting the tigers, saying: "We're spending six or seven days a week caring for them - 24 hours a day.

"We don't call that exploiting - but we do spend a lot of time defending ourselves from attacks.

"It costs money with lawyers and stuff to defend ourselves that could go to caring for these animals."

An animal owner in Ohio released his collection of over 50 exotic animals, including lions and tigers, before killing himself in 2011.

Chaos ensued and the police had to shoot and kill most of the big cats, prompting state legislation that put strict regulations on owners and banned future ownership of exotic animals.

Calls are growing for this to become federal law.

Activists such as Susan Bass from Big Cat Rescue say that needs to happen soon.

"How is this not already illegal? How can this be happening in a country like America?" she said.

"(It's the) same with circuses. Over 40 countries have banned wild cats and animals in circuses, (but) not in the United States.

"We are so far behind in animal welfare and frankly it's embarrassing."