Tests with cylinders of 4 and 8 mm diameter revealed equivalent results. Nature , — Results and discussion a Vortex-induced vibrations Excluding any artificial flow perturbation by immersed cylinders, only forces induced by the laminar flow on the whisker occur, such as VIV. Every frequency and amplitude values for further processing were obtained by automatic averaging over 20 samples of single values. For each species, vibrissae of different sizes were used, taken from comparable positions on the vibrissal pads row D, columns 1, 2 and 3 in the harbour seal and columns 2, 4 and 6 in the sea lion. Nature , — Although, finally, the SNR values of seal and sea lion whiskers were similar, differences in temporal resolution might occur between species.
While dolphins can cope with such conditions by the use of their active sonar system [ 5 , 6 ], this sensory ability has not been demonstrated in pinnipeds yet [ 7 , 8 ]. Vibrissae with known growth histories were resampled at multiple known intervals to control for unknown growth starting dates. Pinnipeds have particularly large F-SCs that can reach a length of more than 2 cm Marshall, This way, most whiskers in the harbour seal face a flow field right in front of the animal with their narrow side, while in the sea lion, the wide side of the whiskers is directed towards the flow field.
The ring sinus is strongly believed to play a crucial role in the biomechanics of the vibrissa. Behaviour 22 , — Oliver found that a blindfolded grey seal in an artificial pool could navigate through a maze of vertical rods without displacing the rods. Sensory function aside, movements of the vibrissae may also indicate something of the state of mind of the animal,  and the whiskers play a role in social behaviour of rats. Based on single-unit recordings from the infraorbital branch of the trigeminal nerve of harbour seals Phoca vitulina and grey seals Halichoerus grypus , Dykes [ 17 ] suggested that the vibrissal system of these marine mammals should allow the haptic discrimination of for example surface structure as well as macrospatial tactile information derived from the shape and size of an object [ 17 ].
The present results indicate that the effective reduction of dynamic forces acting on the hair shaft leads to substantial noise reduction cf. Generally, vibrissae are considered to mediate a tactile sense, complementary to that of skin. Many pinniped species can be considered as opportunistic feeders, hunting on pelagic fishes as well as on benthic prey, for example flatfish or crustaceans. The modulus of elasticity a measure of how the material itself deforms elastically under stress of a harbour seal vibrissa is similar to other keratinous structures and decreases after immersion in water Marine Center Rostock, unpublished data. Every measurement was repeated at three different flow speeds within the maximum range of the flume from 15 to 55 cm s —1. F-SCs are found at the base of the vibrissae of all mammals and constitute complex and richly innervated sensory organs. Click the View full text link to bypass dynamically loaded article content.