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2006-02-08 / Columnists

Pets, Pets, Pets...

by Joanne Anderson

Don’t waste your hard earned cash on a box of Valentine treats for your cat. Fluffy won’t appreciate the loving gesture. Cats have a genetic mutation which leaves them without a "sweet tooth". Felines, tame and wild, may be the rare mammals that have no sweet taste buds. Owners have long wondered why their cats, unlike dogs, were disinterested in desserts. Now they have an explanation.

By examining the DNA of 6 pet cats, a tiger, and a cheetah, a joint American/ British study published last summer found that a non-functioning gene (pseudogene) is the reason cats do not crave sugars. Scientists from the Monell Chemical Senses Center in Philadelphia and the Waltham Center for Pet Nutrition in Britain discovered that two different proteins must hook together to make each sweet receptor on a cat’s tongue.

However, cats do not produce one of these proteins because one of the genes is not working. Therefore, they do not form a normal sweet receptor. The result: cats will ignore anything that tastes or smells of sugar. When cats turn their noses up at sugary offerings, they aren’t being finicky. They just can’t sense sweetness.

The experiment was set up "wine tasting" style to isolate the feline preference. At Monell, cats had a choice of plain water or water spiked with sugar at varying concentrations. Given these choices, the cats never showed a preference or avoidance for the Kat KoolAid. The researchers concluded that the cats were either indifferent or unable to detect the added sugar.

Joseph Brand of Monell noted that feline species have no way to recognize carbohydrates, and survive on a diet of meat and fat. Several evolutionary questions arise: when and why did cats lose their ability to detect sweets, and which came firstthe carnivorous diet or lack of a sweet receptor? It’s unclear yet whether cats’ absence of a "sweet tooth" led them to pursue an all meat diet, or the contrary, as more scientists suspect, that cats were already carnivores, rendering sweet detection a useless skill. Follow up studies are underway, using the DNA of civets, mongoose and hyena, which also evolved from a common feline ancestor, to attempt to pinpoint when the sweet deletion occurred.

Some folks claim their cat shares their ice cream or melon. Despite this, the researchers say that these pets also lack the sweet receptor. In fact, 2 cats from their DNA analysis sample were chosen because they loved marshmallows. They had the pseudogene too. Brand says that, anatomically, flavor is more complex than taste, and that these atypical cats are not attracted to sugar, but to another attribute such as a smell, the salts, or amino acids present in that particular food. Cupid’s confections to your pets. Chocolates can be dangerous to dogs and cats. The theobromine and caffeine in chocolate are toxic to both. Dogs are more likely to be poisoned because they are attracted to sweets, and as a species, are unusually sensitive to theobromine. Just to be safe, keep all candy beyond the reach of your kitties too, since curiosity is the notorious cat killer. Show your 4-legged Valentines how much you adore them by spending more quality time together instead.

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