May 01, 2020

Some domestic cats are known to eat wildlife in addition to the food they are given by their owners. So researchers in the U.S. and U.K. set out to determine just how much wildlife cats eat—by measuring carbon and nitrogen isotopes in cat hair—but instead found themselves stymied by an unexpectedly high variability in cat food ingredients.

The researchers collected carbon and nitrogen isotopes from things a cat might eat, including cat food, to compare against isotopes in cat hair. According to the study abstract, “Variation in C and N isotope values for cat food was very high, even within the same brand/flavor, suggesting that pet food manufacturers use a wide range of ingredients, and that these may change over time.”

The only clear relationship was that the least-expensive cat foods had higher carbon values, indicating a strong presence of corn products in inexpensive cat food. In addition, cat foods from the United Kingdom had lower carbon values, suggesting less input from corn products.

The paper, “High variability within pet foods prevents the identification of native species in pet cats’ diets using isotopic evaluation,” was published online Jan. 22 in the journal PeerJ. The authors are from North Carolina State University, the North Carolina Museum of Natural Sciences, the University of Exeter, and New York State Museum.