Bottlenose Dolphins, Tursiops truncatus, Can Detect Oil
Two trained bottlenose dolphins, Tursiops truncatus, were tested for their ability to detect visually 12 different oils and 22 oil mixtures confined at the surface in small cylinders. Detection thresholds were established in tests using progressively lighter substances. The animals detected 6-mm slicks of crude, residual, and refined motor oils, and diesel slicks thicker than 17 mm. They could not detect 6-mm thicknesses of leaded gasoline or transparent mineral oil. One dolphin's ability to detect oil improved with experience. While blindfolded, one dolphin could detect 12-mm-thick samples of two crude oils, Bunker C and mineral oil, but only when the latter two were churned and contained air bubbles. We conclude that dolphins detect the thicker concentrations of oil that occur near the source of an oceanic spill, but not lightly colored or refined products that tend to disperse into thin films.