page_title: Animal navigation
section_title: Olfaction
hierarchical_section_title: Animal navigation / Mechanisms / Olfaction
caption_attribution_description: Salmon leaping at the Falls of Shin, Scotland
context_page_description: Animal navigation is the ability of many animals to find their way accurately without maps or instruments. Birds such as the Arctic tern, insects such as the monarch butterfly and fish such as the salmon regularly migrate thousands of miles to and from their breeding grounds, and many other species navigate effectively over shorter distances.
  Dead reckoning, navigating from a known position using only information about one's own speed and direction, was suggested by Charles Darwin in 1873 as a possible mechanism. In the 20th century, Karl von Frisch showed that honey bees can navigate by the sun, by the polarization pattern of the blue sky, and by the earth's magnetic field; of these, they rely on the sun when possible. William Tinsley Keeton showed that homing pigeons could similarly make use of a range of navigational cues, including the sun, earth's magnetic field, olfaction and vision. Ronald Lockley demonstrated that a small seabird, the Manx shearwater, could orient itself and fly home at full speed, when released far from home, provided either the sun or the stars were visible.
context_section_description: Olfactory navigation has been suggested as a possible mechanism in pigeons. Papi's 'mosaic' model argues that pigeons build and remember a mental map of the odours in their area, recognizing where they are by the local odour. Wallraff's 'gradient' model argues that there is a steady, large-scale gradient of odour which remains stable for long periods. If there were two or more such gradients in different directions, pigeons could locate themselves in two dimensions by the intensities of the odours. However it is not clear that such stable gradients exist. Papi did find evidence that anosmic pigeons (unable to detect odours) were much less able to orient and navigate than normal pigeons, so olfaction does seem to be important in pigeon navigation. However, it is not clear how olfactory cues are used.
  Olfactory cues may be important in salmon, which are known to return to the exact river where they hatched. Lockley reports experimental evidence that fish such as minnows can accurately tell the difference between the waters of different rivers. Salmon may use their magnetic sense to navigate to within reach of their river, and then use olfaction to identify the river at close range.
caption: Returning salmon may use olfaction to identify the river in which they developed.
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