Cats are the only mammals that cannot taste sweetness.

In 2005, researchers at the Monell Chemical Senses Center in Philadelphia discovered that all cat species, including lions and tigers, share a genetic defect that prevents them from tasting sweets. This is caused by a mutation in the Tas1r2 gene. This gene normally works with the Tas1r3 gene to create a protein receptor that detects sugar on the tongue.Because cats are obligate carnivores, they do not need to identify carbohydrates or sugars for survival. Over millions of years of evolution, the Tas1r2 gene became a pseudogene, meaning it is still present in their DNA but no longer functions. This makes the cat family unique among mammals, as even other carnivores like dogs and bears have retained their sweet receptors.While they cannot taste sugar, cats have evolved other specialized receptors to evaluate their food. Their tongues are highly sensitive to adenosine triphosphate (ATP), which is a molecule that provides energy to all living cells and is abundant in meat. This allows them to gauge the freshness and nutritional value of prey without needing to detect sweetness.Interestingly, some cat owners report that their pets enjoy sweet foods like ice cream or cake. Scientists believe this is not because of the sugar content, but rather because the cats are attracted to the high fat or protein content in those foods. Their lack of sweet receptors also protects them, as high-sugar diets can lead to serious health issues like diabetes in felines.