Material composition discrimination of cylinders at different aspect angles by an echolocating Dolphin

An echolocating dolphin was trained to discriminate between the material composition of two cylinders oriented at different aspect angles. The two targets for the first task were a hollow aluminum and a hollow stainless steel cylinder of the same dimension. For the second task, the targets were the hollow aluminum cylinder and a cylinder of coral rock aggregates encased in degassed epoxy. The dolphin could discriminate the aluminum and steel cylinders perfectly at aspect angles of 0° and 10° (at 0°, the longitudinal axis of a cylinder was perpendicular to the dolphin). The dolphin had its lowest performance (79% and 81% correct) when the cylinders were at aspect angles of 45° and 90°, respectively. The echoes from the aluminum and steel cylinders were the most similar at 45° and 90° the two angles at which the dolphin’s performance was the lowest. The dolphin performed the second discrimination task between the hollow aluminum and coral rock cylinders almost perfectly, at all aspect angles considered. Dif...