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It is well documented that shark squalene—oil from their livers—is an ingredient in some cosmetics, such as lipstick and mascara. Now, new research shows that shark squalene is in pet food, too. DNA analysis reveals that at least some of it is coming from endangered species.

Shark biologist Diego Cardeñosa, a doctoral student at Stony Brook University in New York, analyzed 87 pet foods from 12 different brands, including canned wet food, dry food, and treats, as well as 24 cosmetics from 15 different brands. He purchased the products online and in supermarkets. Using a technique called DNA barcoding, which uses small fragments of DNA to identify species, he found evidence of several endangered shark species in the food including scalloped hammerheads and shortfin makos.

“I’m quite disgusted to think of the hammerhead—an amazing animal—in canned cat food,” says Susana Caballero, a biologist at the Universidad de los Andes in Colombia, who was not involved in the study. “It’s an insult to that species.”

In heavily processed products it can be difficult to find enough quality genetic material to reliably identify a species. However, Cardeñosa’s work used a novel method that allowed him to use even heavily degraded DNA not possible with older techniques. This advance is what makes the project so exciting, Caballero says.

In total, Cardeñosa found at least two shark species in pet food, including mostly the shortfin mako, which was recently listed as endangered on the International Union for Conservation of Nature’s Red List.

“It was quite shocking, to be honest, to see so many pet food products with mako in them,” he says.

In beauty products, Cardeñosa found genetic material from blacktip sharks, blue sharks, and scalloped hammerheads, a critically endangered species.

Cardeñosa and other biologists do not think sharks are being killed specifically for pet food, which is why he is reluctant to mention which brands he tested. Instead, he says manufacturers are likely using meat or other parts that would otherwise go to waste.

John Hyde, a fisheries geneticist from the National Oceanic and Atmospheric Administration who was not involved in the study, says this approach maximizes the use of the harvested animals and reduces waste. The question, Hyde says, is: “should the feed manufacturers be lauded for full utilization of fishery products, or vilified for supporting exploitation of species that may or may not need extra protection?”

Fishing for many shark species is legal in the United States and elsewhere. Some species, however, are protected either by national laws, such as the US Endangered Species Act (ESA), or international regulations, such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Some sharks, such as shortfin mako, are protected by one (CITES) but not by the other (ESA). Legality often depends on where or how a shark was caught. This makes it difficult to say whether a shark’s presence in pet food is illegal.

Cardeñosa’s stance is that even if there is nothing illegal happening, “it’s a matter of letting consumers have the choice.” Inadequate labeling makes it impossible for a consumer to know if the food or cosmetics they are buying contain shark products, he says.

Beauty products, for instance, only list squalene in the ingredients, but squalene can also be derived from plants. The pet foods had generic terms, such as white fish or ocean fish, that don’t refer to a specific species.

Hyde says that while numerous studies have demonstrated the extent of seafood fraud in food meant for people, there have been far fewer studies examining other markets. “All of this makes us more aware of what we are eating,” he says.

Hyde hopes that work like Cardeñosa’s will help improve traceability and accountability of fishery products. “Ideally, we could track these products to specific fisheries where we could know whether the species was being managed and harvested in a sustainable fashion.”

“Better labeling and more transparency is the key here,” says Cardeñosa.