Why does one cat go crazy for chicken, while another craves beef? Or why does your cat only lick the gravy off of one wet food but gobble down another? As it turns out, your cat’s nose often knows. The smell of cat food may not whet your appetite, but aroma is nearly everything for your feline when it’s deciding when and what to eat, according to recent research.

Last year, a group of Hungarian scientists conducted a study on how cats decide which food to consume when given a choice of cat foods. The results, which were published in the Journal of Animal Physiology and Animal Nutrition, found that if cats determine the scent of one food is more attractive than another, they will eat that food without even tasting the food with a less attractive odor. Cats resort to sense of taste only if none of the meals they are offered has an agreeable smell.

But what could be going on in your cat’s mind when it puts food to the nose test? Here are some likely explanations for the method behind the sniffing madness.

The Importance of Proteins and Fats
When your cat sniffs its food, odors linked to proteins and fats often come up winners, and for good reason. Proteins and fats are the single most important ingredients in a feline diet. That’s because in the wild, cats are carnivores. They live on diets composed almost entirely of meat, with only a small amount of vegetables and essentially no grains. House kitties, however, can benefit from certain high quality grains, which serve as energy-producing carbohydrates. These may include corn meal, rice flour, grain sorghum and wheat. The smell of these ingredients, however, will not entice your cat in the same way that meaty odors can.

Only the Right Protein Will Do
“Cats are much more finicky than dogs,” says Dr. Joseph Wakshlag, DMV, assistant professor of clinical nutrition at the Cornell University College of Veterinary Medicine. “They like the high protein, higher fat foods, but their diet is also very driven by the need for certain amino acids.” Amino acids are present in animal-based protein sources, so your feline may be sniffing out these subtle protein components too. According to the American Society for the Prevention of Cruelty to Animals, for both dogs and cats, there are 10 amino acids that are considered essential in the diet — histidine, isoleucine, arginine, methionine, phenylalanine, threonine, tryptophan, valine, and lysine. Cats also need taurine, another substance essential for felines, but one which canines can produce on their own, Dr. Wakshlag says. That is one important reason why dog food is not a nutritionally sufficient diet for cats.

Part Quirkiness, Part Science
The peculiar taste preferences of cats are familiar to many a pet owner. “Certainly you’ve heard the stories of the finicky cat who will only eat tuna,” says Nancy Peterson, a registered veterinary technician and issues specialist at the Humane Society of the United States. Many a household with more than one cat will have different items on the dinner menu each night – one cat may be partial to dry, fish-flavored food, while another may only eat moist chicken. Like people, cats develop preferences to different flavors, but in their case, they are driven by their discriminating sense of smell.

Cats have taste buds, but only 473, far fewer than the 9,000 taste buds on the human tongue, according to Cats International, a non-profit educational organization. Cats can taste salty, sour and bitter, but new research indicates that they don’t have a sweet tooth. Researchers at the Monell Chemical Senses Center in Philadelphia published a study in 2005 in the journal PLoS Genetics arguing that cats have a genetic mutation that has made their taste buds out of order for detecting sugar. The study helped scientists understand that a cat’s indifference to sugar supports their dependence on an all-meat diet, unlike humans and other animals that have more cravings for fruits and starches.

Introducing New Flavors and Foods
There are many good reasons to introduce a variety of flavors and textures into your cat’s diet, experts say. Cats can easily develop strong preferences for one type of food and decline all others, which can be a problem. Canned tuna, for example, lacks some of the vital amino acids that cats need. While still kittens, Dr. Wakshlag advises pet owners to introduce not only a variety of flavors but, more importantly, textures. “The idea is to change it around so a cat doesn’t develop any specific preference,” he says.

As cats age, they become more prone to diseases, such as kidney disease or tooth decay. A cat that has only eaten dry food all its life may be averse to switching to a moist food. Dry foods contain only 6 to 10 percent moisture, compared with 75 percent of some canned foods, according to Cornell University’s College of Veterinary Medicine. Many cats tend to avoid the water bowl and a wet food is one way of ensuring they get their daily dosage. “Look at what a mouse is and it’s more close to canned food than dry,” Dr. Wakshlag says, who owns two cats, ages 11 and 13.

To help an older cat transition, Peterson advises adding more moist food or food of a different flavor to your cat’s preferred diet a little at a time. “By the fourth of fifth day,” she says, “hopefully your cat has switched to this new food.” In essence, you will have retrained your cat’s nose to accept the different aroma mix.