While the Penguins beat the Flyers, 4-2, animal rights activists insist the penguins lost. (Charles LeClaire/USA Today Sports)

The animal rights group PETA has informed the Pittsburgh Penguins that they’re skating on thin ice after the NHL toted out actual penguins to appear at a game Saturday. The penguins, which came from the Pittsburgh Zoo and PPG Aquarium, didn’t exactly look pleased to be there, especially after a pyrotechnic display exploded unexpectedly behind them, giving them a clear scare that sent them scrambling for cover.

While the Internet complained about the display first, PETA also chimed in, sending a formal letter to the NHL franchise criticizing the decision to tote out the live animals at the special “Stadium Series” game at Heinz Field.

“It’s inherently stressful for wild animals — who naturally shun contact with humans and are extremely sensitive to environmental changes — to be hauled around, used as props, and exposed to noisy crowds, with or without explosives going off,” the letter, reprinted in full by the Pittsburgh Post-Gazette, states. “Hockey fans come to see talented athletes compete, not shy animals terrorized.”

The Penguins, meanwhile, have not commented on the issue, as the Post-Gazette points out that it wasn’t the team but the NHL that organized Saturday’s display.

The zoo, for its part, has denied that the scene Saturday was at all harmful to the animals, including the pyrotechnic display.

“The loud pop from the pyro technical display temporarily startled the penguins and their first reaction, similar to a human’s when startled, they flapped their wings,” the zoo said in a statement to the Post-Gazette. “It was less than 10 seconds and the penguins were back to normal and exploring and playing on the ice.”

“In addition,” the statement continues, “it was a great enrichment opportunity for our penguins to be introduced to new sounds, sights and smells.”

The idea of animal welfare concerning zoos and other attractions has made headlines recently, as the Ringling Bros. and Barnum & Bailey Circus announced in January it would be folding its operation in May after deciding to end its controversial elephant act.

The act had been the subject of animal rights activists’ protests for years. Not only did PETA rejoice about the end of the elephant act, but so did the Humane Society of the United States, which said, “It’s just not acceptable any longer to cart wild animals from city to city and have them perform silly yet coercive stunts.”

SeaWorld also recently decided to end its killer whale theatrics, which couldn’t recover after the 2013 animal rights documentary “Blackfish” created a PR nightmare for the brand by raising the curtain on the shortened life expectancy of the whales in captivity.

SeaWorld denied the allegations made in the film, calling it “emotionally manipulative,” but the film struck a chord with critics and vacationers alike.

“It’s hard to imagine anyone coming out of this movie and not swearing off the next vacation trip to Orlando, San Antonio or San Diego,” Washington Post movie critic Michael O’Sullivan wrote after the film’s release.

In Thursday’s letter to the Penguins, PETA brought up the changing tide of opinion when it comes to animal rights and asked, “Will you please let us know that you won’t use live animals for promotions in the future?”

The NHL has yet to respond.