NEW YORK: While mammals are known to be not able to use their sense of smell when in water, a U.S. scientist has identified at least two tiny semi-aquatic mammals, which can hunt under water using air bubbles generated from their own breath to smell.
Kenneth Catania, a biologist at the department of biological sciences at Vanderbilt University, Nashville, Tennessee in the U.S., says the star-nosed mole and the water shrew are able to smell food under water.
Writing in the Nature, he says this has come as a total surprise because the common wisdom is that mammals cannot smell underwater as it is not possible to breath in air, which carries smell to the olfactory epithelium, situated in the nasal cavity which identifies odor.
Catania began studying the possibility of mammals sniffing under water when he noticed the star-nosed mole he was observing blew a lot of bubbles while swimming. He and his team set up baits of earthworm or fish scent, covering it with a steel mesh, which prevented any of the star-nosed moles in the experiment sniffing the trail with any other contact, but only through the air bubbles that pass through. The rate and amount of air exhaled and inhaled were also measured. The team tested five moles, which followed the trail to reach a reward with 85 per cent accuracy, compared to 50 per cent accuracy when the size of the mesh was reduced to prevent air bubbles going through.
The team carried out similar experiments using water shrews, which also showed the same results.
Catania says star-nosed moles and water shrews seem to have adapted their olfactory system for use underwater. He said the volumes of air expired and re-inspired, the airflow rate, the frequency were all remarkably similar to sniffing in air.
Catania says it needs to be investigated whether other semi-aquatic mammals are capable of smelling under water and whether this capability is for only smaller mammals.
