The vibrissal system of pinnipeds such as harbor seals (
) or California sea lions (
) serves not only for the detection and identification of objects by direct touch, but also detect and analyze water movements (hydrodynamic stimuli). These two species represent two different types of vibrissae, one with an undulated outline (harbor seal) and one with a smooth outline (sea lion). In our recent set of studies, we analyzed the hydrodynamic stimuli generated by stationary fish and by escaping fish, and tested the ability of pinnipeds to analyze artificial hydrodynamic stimuli that share certain features with natural hydrodynamic stimuli. Biomechanical studies of isolated vibrissae in a flow tank show different signal-to noise ratios for the two species that are consistent with their different performance in behavioral experiments, and can be explained by fluid-structure interactions.