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Underwater 'sniffing' by semi-aquatic mammals


Terrestrial species that forage underwater face challenges because their body parts and senses are adapted for land — for example, it is widely held that mammals cannot use olfaction underwater because it is impossible for them to inspire air (sniff) to convey odorants to the olfactory epithelium1,2,3,4,5. Here I describe a mechanism for underwater sniffing used by the semi-aquatic star-nosed mole (Condylura cristata) and water shrew (Sorex palustris). While underwater, both species exhale air bubbles onto objects or scent trails and then re-inspire the bubbles to carry the smell back through the nose. This newly described behaviour provides a mechanism for mammalian olfaction underwater.

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Figure 1: Star nose of the mole (Condylura cristata) breathing air while underwater.
Figure 2: Underwater olfaction in semi-aquatic moles and shrews.
Figure 3: A diving American water shrew (Sorex palustris).

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Supplementary information

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Video 1

Video 1 shows wide angle, slow motion view of a star-nosed mole sniffing underwater.

Video 2

Video 2 shows star-nosed mole sniffing a piece of wax underwater - note that the bubble contacts the wax.

Video 3

Video 3 shows a star-nosed mole “sniffing” through a metal grid to control for touch with the star.

Video 4

Videos 4 and 5 were captured with a Cannon XL-1 video recorder and show a star-nosed mole during the scent tracking behavior.

Video 5

Videos 4 and 5 were captured with a Cannon XL-1 video recorder and show a star-nosed mole during the scent tracking behavior.

Video 6

Video 6 shows a water shrew sniffing various objects underwater in slow motion.

Video 7

Video 7 shows a water shrew during the scent tracking behavior.

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Catania, K. Underwater 'sniffing' by semi-aquatic mammals. Nature 444, 1024–1025 (2006).

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