In daylight, and again at night under a shading canopy, we observed the behavior of bottlenose dolphins (Tursiops truncatus) allowed to swim freely in a pool with three surface divisions, one of which contained either clear mineral oil, dark-tinted mineral oil, or a thin sheen of refined motor oil. Overall, they avoided oil both during the day and at night. The response broke down when we presented them with a thin sheen, especially at night; we suggest that such conditions represent the threshold for their ability to detect oil or their desire to avoid it. Irrespective of light conditions, the dolphins' tactile sense played a more important role than vision in perceiving, and ultimately avoiding, oil. The strength of their basic reaction dampens our fear that they might be unknowingly subjected to prolonged or repeated exposure to oil at sea.
Microbial Destruction Mineral (Oil) Motor Oil
