Polar Bear Living at Zoo Inside Mall is in 'Mental Decline,' Activist Groups Claim

"[Pizza's] case is most pressing, [but] that's not to say he's doing the worst. There are hundreds of animals at that aquarium," a representative said.

A destitute polar bear, who lives in what is dubbed "The World's Saddest Zoo," may have finally reached its breaking point.

Read: Animals Are Living in 'Horrifying' Conditions at China Zoo, Activists Say

New footage released by animal rights activist group Humane Society International shows Pizza, a polar bear living in a shopping mall in China, in "mental decline," they claim.

In the video, Pizza can be seen pacing his cage back and forth, shaking his head and gnawing on the cage, as shoppers snap pictures and taunt him through the glass.

In a statement, the organization's veterinary advisor Professor Alastair Macmillan explained the behavior is "induced by frustration and poor welfare.

"This is the animal's attempts to cope with stressful, aversive situations, such as barren enclosures, boredom and constant disturbance by visitors," he continued.

The polar bear, which is one of the over 500 animals living at the Grandview Mall Aquarium in Guangzhou, China, made headlines after several animal rights groups argued the conditions in which it is kept are inhumane.

"[Pizza's] case is most pressing, because of the way he acts in the video," Raul Arce-Contreras of the Humane Society told InsideEdition.com. "Our scientific advisors have said he's not doing good, in terms of mental health, because there's no enrichment in that cage. It's some glass, and ice. It's a small box he's stuffed in.

"That's not to say he's doing the worst," he continued. "There are hundreds of animals at that aquarium."

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As activist groups put pressure on the aquarium to hand Pizza over to a more suitable facility, the Yorkshire Wildlife Park in England has offered to give the bear a home.

The Chinese aquarium rejected its offer.

In a statement to The New York Times earlier this week, the aquarium said: "Pizza is very healthy."

Animal rights group are continuing their efforts to publically pressure Chinese officials to shut down the zoo.

Watch: World's Saddest Bear Is Rescued After Living on Nothing But Beer, Bread and Selfies