Feb. 9, 2006 — Rats need only one sniff to take their bearings on a tasty morsel, say researchers who have discovered what may be the olfactory equivalent to stereo hearing in the common rodents.

It turns out that rats use their two nostrils with what appears to be far more efficiency than humans do, and may be a lot like some other scent-oriented animals.

In just 50 milliseconds rats can not only identify an odor, but can tell in which nostril an odor is stronger and then head for it.

"Rats are smart and great at odor-related tasks, so they were a good system to get at the question in detail," said olfactory researcher Upinder Bhalla of the National Center for Biological Sciences in Bangalore, India. Bhalla, Raghav Rajan and J.P Clement published their findings in the Feb. 3 issue of the journal Science.

"I didn't believe that the effect was real at first," said olfactory researcher Leslie Kay of the University of Chicago, commenting on the new work. "They've come closest to showing that it exists."

Building on the work of other researchers who had discovered that rats draw air into the nostrils sideways, Bhalla and his colleagues set up a series of laboratory tests to verify that rats are, indeed, able to use that sidewise air flow to detect the direction of banana oil and other aromas.

The rats were trained to lick right or left water spouts after sniffing the air for a right or left aromatic clue. They were also tested to rule out effects from such other sensory apparatus as whiskers that might detect the direction of the odor-carrying.

What the Indian team discovered is that 90 percent of the neurons in the scent-processing part of rat brains respond differently depending on which nostril detected the scent first. That, plus the fact that it took the rats as little as one sniff and 50 milliseconds to decide on the direction, seems to indicate that rats are using their noses to collect olfactory snapshots of the world around them.

As for other animals, Bhalla told Animal Planet News that the wide spacing of horse and cow nostril suggests they may have the same stereo-smelling capabilities as rats.

"And hippos too," Bhalla said. "I would not be surprised if many other organisms can do this too."

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Primary Classification: Rattus (Rats)
Location: Worldwide
Habitat: Areas populated by humans, as well as forests and deserts.
Diet: Omnivorous
Size: Up to 10 inches in length and 1 lb in weight.
Description: Large, dark eyes; pointy noses; cupped ears; short fine hair on tails; long, slender bodies; back legs longer and stronger than their front legs; clawed feet covered with short, silky fur.
Cool Facts: They have glands on the bottom of their feet, so they leave a wet scent trail wherever they walk. They use their tails for many functions including balance, temperature control and communication.
Conservation Status: Common

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