Eastern American moles use two different mechanisms to locate odours at close- and long-range, reports a study in Nature Communications this week. The findings provide new insight into olfactory processing in mammals that are strongly dependent on their sense of smell.
In many sensory systems, stimuli from more than one point of input (e.g. two eyes), are necessary for the accurate location of the target. However, whilst this is true for many sensory systems, there has been much debate as to whether this theory also holds for the olfactory system. Kenneth Catania tests this theory in blind Eastern American moles by using food to lure the animals and blocking a single nostril input, or crossing the inputs using open plastic tubes. He finds that blocking one nostril causes the animals to veer toward the open nostril, even if this is away from the direction of the food. This behaviour suggests that they are “pulled” toward the open nostril. However, somewhat surprisingly, crossing the nostril inputs repels the voles from the food, although they still locate it eventually.
The authors suggest that the processing of olfactory cues, at least for poorly sighted animals, requires two strategies: one for longer distances and another for close range, where gradient of olfactory cues are relatively steep. They conclude that, similar to hearing and vision, integration of these signals in the brain plays a crucial role in determining the stimulus location.