Rats Smell in Stereo.

Upider Bhalla from the National Centre for Biological Sciences in Bangalore, India and colleagues discovered that rat smell in stereo:

Researchers in India have discovered that a single sniff is enough for a rat to locate the source of an enticing aroma.

Their work shows that rats can effectively smell in 'stereo': their two nostrils work independently in much the same way as our ears, with contrasting signals to the brain creating a spatial understanding of sensory information.

http://www.nature.com/news/2006/060130/full/060130-10.html