Behavioural use of seismic cues by the sandswimming lizard Scincus scincus

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Abstract
The sandfish lizard, Scincus scincus (Linnaeus) inhabits the deserts of Africa and the Middle East and spends most of its time buried in the sand. Laboratory experiments have determined that Scincus can respond and orient to insects on the sand surface by detecting vibrations produced by movements of the insects. When buried, Scincus can detect and respond to crickets and mealworms moving over the surface at distances up to about 15 cm. These responses are guided by vibratory cues, not olfactory cues, as the lizards respond much less frequently to dead insects placed on the surface at equal distances. The lizard obtain directional information from the vibrations, and can localize the insects, orient toward them, and emerge from the sand to capture them. Scincus buried in the sand also respond differently to crickets and mealworms; the faster moving crickets elicit appropriately quicker emergences. Tests with artificial signals have demonstrated that the lizard respond differently to different temporal pattern of seismic signals; fast strike rates, perhaps analogous to fast footstep rates of insect prey, elicit faster emergences. Different velocities of the seismic source also elicit different responses; faster moving sources produce quicker emergences. The lizards therefore are responsive to different aspects of seismic signals that carry certain types of information; in this case, Scincus can distinguish between different types of prey (slow and fast-moving) and respond appropriately. When walking on the surface of the sand, Scincus often displays a peculiar behaviour of plunging its head into the sand. Experiments determined that this behaviour aids lizards in detecting vibrations produced by insects moving through the sand, and presumably facilitates transmission of sandborne vibrations to the inner ear.