Detection of water surface waves by nile crocodiles (Crocodylus niloticus)

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The 23 species of crocodiles belong to the largest living reptiles. Depending on their age, crocodiles prey on insects fallen into the water and on frogs, fish and terrestrial vertebrates. The skin of all crocodiles contains Dome Pressure Receptors (DRPs). These receptors respond to direct touch and to subsurface and surface water motions. Although studies have shown that crocodiles use their DRPs to sense water surface waves, quantitative experiments that have investigated the full behavioral capability of this sensory system are missing. In the applied research project we want to determine the behavioral thresholds of crocodiles to sinusoidal water surface waves. In addition we want to study to which precision crocodiles can discriminate water surface waves that differ in frequency, frequency content and in frequency or amplitude modulation. In further experiments we will investigate whether crocodiles can recognize a surface wave signal in the presence of a second surface wave train generated at a different location. Finally we want to find out whether and for how long crocodiles can remember a learned discrimination task.