A new study seems to explain why cats are apparently fussy eaters – they might have taste buds more sensitive to bitter foods, possibly to protect them from consuming potential toxins. The paper is published in PLOS ONE.
When the genome of cats was analysed, it was found that they share pieces of DNA with herbivores: the researchers discovered 12 specific genes coding for bitter taste receptors that allow the latter to determine whether a potential food is beneficial or deleterious.
Bitter tastes are often indicative of harmful toxins found in some plants or unripe fruits. Conversely, sweet tastes generally suggest the presence of sugars that constitute an energy source. Cats, on the other hand, cannot taste sweetness anymore. The shift in animal diets over time is thought to be accompanied with mutations in genes that code for taste. Since cats feed exclusively on meat, they do not need taste buds – the receptors – to detect sweetness, and so they have gradually lost those genes. How to explain that they can taste bitter when they do not eat plants, then? How come they have not lost the bitter taste receptor genes?
To reconcile between the findings and the logic of the evolution of the genes, one of the scientists, Peihua Jiang, a molecular biologist, incorporated the cat taste receptor gene into human cells in laboratory such that the end result was a taste receptor. When testing it with chemicals, Jiang found that it would respond to bitter chemicals from toxic plants as well as to those stimulating human bitter receptors.
Therefore, cats seem to not have lost the ability to detect bitter tastes.
The authors of the new study speculate that the bitter receptors might allow cats to sense toxins (that are often bitter in taste) in the skin or bodies of foods like frogs, toads and other animals that cats often bring to their owners as gifts.
Past research also suggest that cat taste receptors might be particularly sensitive to bitter chemicals. This enhanced sensitivity might account for cats’ reputation of being picky eaters. Another important finding of the researchers of the new study is that other meat-eating animals such as dogs, ferrets, and polar bears also have the genes in question. But, again comes the argument that cats might, perhaps, detect bitterness better as this would explain why dogs can eat anything as opposed to cats in spite of the fact that both have the genes.
So, next time you criticise cats for being picky, remind yourself that, unlike you (and dogs), they might just be better at detecting bitterness.