Star-nosed Mole (Condylura cristata) “sniffing” underwater
The kind of thing to drive any formerly self-respecting paleontologist nuts: underwater olfaction in mammals. Smell is an important sense for mammals, no surprise to anyone who has stepped into a Sephora outlet recently. Though we are generally far more conscious of sight and sound, we’re still led around by the nose far more than we would guess…especially when it comes to eating and mating.
And other mammals, especially those who have stuck to more respectable mammalian lifestyles (i.e. grubbing around for worms and bugs at night), put humans to shame in the olfaction department. Still, the announcement that some specialized “insectivorans” (or soricomorphs if you’re T.C. like that) are able to smell underwater came as a surprise – to me at least.
As seen in the photo above, this amazing feat is accomplished by expiring a small bubble of air then re-inspiring it. This allows these air-breathing mammals to safely search for odors underwater as they search for prey. Notably, many other aquatic mammals rely exclusively on other senses especially hearing and touch; whales have apparently little or no sense of smell judging from their brains.
A detailed analysis of the tactile and olfactory abilities of the American Water Shrew (Sorex palustris) in PNAS, expands upon the initial report of underwater smelling by shrews and moles. Like the previous Nature paper there are awesome photos and slow-mo videos documenting this amazing behavior, highly recommended.
The elaborate experiments by Catania and co. showed that S. palustris uses a combination of tactile (via whiskers) and olfactory clues to evaluate potential prey items. One video shows a shrew puzzled by an artificial cricket which apparently “feels” right but “smells” wrong. They also used experiments to rule out echolocation or electroreception – strategies employed by other mammals that forage underwater.
As for the paleontological lament: it took a serendipitous flash of insight plus the availability of high speed cameras and infrared lighting to bring this interesting behavior to light. One has to wonder how many strange behaviors among fossil taxa, peculiar and mundane, have yet to and may never be guessed at.
Interestingly, aquatic olfaction has been suggested in plesiosaurs based upon skeletal evidence, but I suspect we’ll be waiting awhile for the slow-mo vid.