It’s said there are cat people, and there are dog people. Personally, I like both, but if I had to state a preference, I’d probably give the edge to cats.
It’s not very often I have an excuse to write about them in this column, but this week I do, because by some coincidence, two science items related to cat senses came to my attention within a few days of each other.
Anyone who has a cat has tales of the peculiar things it likes to eat. My childhood cat, Tiger, liked raw eggs, bits of cheese (nothing too peculiar there)—and chocolate chips.
According to a new study by geneticists, though, it wasn’t because he had a sweet tooth: it turns out cats don’t have such a thing (unlike dogs, who most definitely do).
In mammals, both sugars and artificial sweeteners are detected by special taste bud receptors that are coded for by two genes. A study published in the inaugural issue of the Public Library of Science’s journal Genetics by researchers from the U.S. and Britain says that in both domestic and big cats, one of these genes isn’t functional. That means the sweet receptor can’t be formed, and that means nothing tastes sweet to cats. Other than this one “blind spot,” cats have a normal sense of taste, the researchers say.
So why did Tiger like chocolate chips? Probably because of the high fat content.
Cats, unlike dogs, are strict carnivores: in the wild, they eat other animals, and that’s all they eat. A taste for sweetness is therefore of no advantage to them, whereas for animals that also eat plants, a taste for sweetness helps draw them to fruits and vegetables that are ripe and non-poisonous (poisonous substances usually taste bitter). Scientists aren’t sure which came first, though: did cats’ ancestors lack a taste for sweetness, and that led to them becoming more and more carnivorous, or did they lose their taste for sweetness because they were carnivorous and had no use for it?
“This research provides a molecular explanation for the common observation that the cat lives in a different sensory world than the cat owner,” the researchers state in their summary of the paper’s findings.
Another cat behavior that leads to the same observation is the feline reaction to catnip.
To a human, catnip smells like nothing special. For some cats, though, smelling catnip leads to sniffing, licking and chewing, followed by head-shaking, body- and head-rubbing, and then repeated head-over-heels rolling. It’s downright embarrassing to watch, especially since cats generally have such a self-contained, dignified mien.
David Barry (not to be confused with humorist Dave Barry), in the “What’s That Stuff?” column in the August 1 issue of Chemical and Engineering News, explains that the active ingredient in catnip is a compound called nepetalactone. There are other related compounds that produce the same classic catnip behaviors.
Scientists don’t have a firm grasp on exactly why catnip produces the response it does in cats. About all they’re willing to say is that cats seem to have receptors for these compounds primarily in their olfactory system, although there may also be some in their mouth…which is pretty obvious to anyone who has seen a cat react to catnip.
Interestingly, all cats are indifferent to catnip until they are about three months old. Even after that, as many as half of all cats remain indifferent. Sensitivity to catnip is inherited. A kitten who has just one catnip-sensitive parent has a 50 percent chance of inheriting the sensitivity, while a kitten with two catnip-sensitive parents has a 75 percent chance. No link has been found between catnip sensitivity and the cat’s sex, color or breed.
Catnip is a relative of basil, oregano and spearmint, all of which produce flavorful and aromatic essential oils. The leaves, stems and seedpods are covered with microscopic bulbs that store the oil until they reach maturity and burst—or until something brushes up against them, like a cat.
Humans have been known to use the plant: before Asian teas made it to Europe, a tea made of catnip leaves was popular: it’s supposed to be calming, like chamomile tea, and in folk medicine, the plant is believed to have a variety of medicinal properties. That’s what led to it being brought from Europe to North America. It’s now widespread across Canada and the U.S.; in Canada, it’s cultivated primarily in Alberta and British Columbia.
That being the case, it’s just as well it doesn’t affect humans the same way it affects cats.
B.C., after all, has enough of a reputation for growing, um, “plant-based pharmaceuticals” as it is.