The Guggenheim Museum has pulled several controversial works from an upcoming survey of Chinese contemporary art, following protests and alleged threats stemming from the pieces' treatment of animals.

On Monday evening, the museum released a statement explaining its decision to remove three pieces from a highly-anticipated exhibition, Art and China After 1989: Theater of the World, "out of concern for the safety of its staff, visitors and participating artists."

Among the three excluded works was a video showing pairs of pit bulls running at each other on a treadmill called "Dogs That Cannot Touch Each Other," and "A Case Study of Transference," depicting tattooed pigs having sex. The museum also pulled the exhibition's signature piece, "Theater of the World," which would've featured live reptiles and insects fighting for survival in a heated enclosure.

"Although these works have been exhibited in museums in Asia, Europe, and the United States, the Guggenheim regrets that explicit and repeated threats of violence have made our decision necessary," the museum's statement continued.

A preview of the exhibition first sparked the ire of animal rights advocates earlier this month, prompting over half a million people to sign an online petition demanding the museum pull the pieces, along with forceful condemnations from PETA, the ASPCA and celebrities such as Ricky Gervais.

In a letter sent Monday to the museum's director, PETA encouraged the Guggenheim to adopt guidelines mandating that no artwork cause physical or psychological pain to any animals. "People who find entertainment in watching animals try to fight each other are sick individuals whose twisted whims the Guggenheim should refuse to cater to," PETA President Ingrid Newkirk wrote.

The ASPCA also released a statement on Monday, saying that while they "fully support artistic expression," the organization "strongly opposes any use of animals in art or entertainment if it results in pain or distress to the animals, which is clearly the case in this video [above]. Such treadmills are typical of brutal dog fighting training regimens, and the mere positioning of animals to face each other and encourage aggression often meets the definition of illegal dog fighting in most states."

The Guggenheim appeared to be holding firm until Monday night, with one spokesperson previously declaring "it was not a question that it would stay in the exhibition." That statement acknowledged the upsetting nature of the artwork, and urged the angered parties to consider "what they may be saying about the social conditions of globalization and the complex nature of the world we share."

Ultimately, the Guggenheim cited "threats of violence" as their reason for reversing course, though a representative for the museum did not respond to requests to elaborate on the source of those threats. In their statement on Monday, the museum noted that "we are dismayed that we must withhold works of art. Freedom of expression has always been and will remain a paramount value of the Guggenheim."

Reached for comment about the news, Gervais told Gothamist, "I appreciated the wave of concern that caused such a prestigious and respected establishment to accept that animal welfare comes before entertainment."