The muzzles of weasels are pointed, providing ample space for the complex turbinal bones inside the nasal cavity and suggesting that weasels have an excellent sense of smell. Weasels use smell more than vision when hunting, although less than hearing (Gillingham 1986), and they mark their home ranges with complex, informative scent signals (Chapter 8). Herman (1973) tested three least weasels in a Y-maze, 30 times each, to see whether they could distinguish which arm of the maze had previously been travelled by a rodent, and found (to no one's surprise) that they could. Herman made sure that the weasels were responding to scent by running tests both in daylight and in the dark and by offering sound cues at the ends of both arms of the Y-maze but scent in only one. The time each weasel spent in the maze varied from around 140 to 180 seconds at first, whether they got a reward or not. When a correct choice was reinforced by gaining access to the rodent, they learned after about 15 trials to follow the scent trail more quickly to the right door, and after 60 trials their running time was down to less than 30 seconds.

The difference between the results reported by Gillingham and Herman are not necessarily as contradictory as they appear. It may be simply that all the experimental animals could perceive both sounds and smells but reacted to whichever was the most informative in the circumstances.

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