Responses to familiar and unfamiliar objects by belugas (Delphinapterus leucas), bottlenose dolphins (Tursiops truncatus), and Pacific white-sided dolphins (Lagenorhynchus obliquidens).

Previous research with bottlenose dolphins (Tursiops truncatus) demonstrated their ability to discriminate between familiar and unfamiliar stimuli. Dolphins gazed longer at unfamiliar stimuli. The current study attempted to extend this original research by examining the responses of three species of cetaceans to objects that differed in familiarity. Eleven belugas from two facilities, five bottlenose dolphins and five Pacific white-sided dolphins housed at one facility were presented different objects in a free-swim scenario. The results indicated that the animals gazed the longest at unfamiliar objects, but these gaze durations did not significantly differ from gaze durations when viewing familiar objects. Rather, the animals gazed longer at unfamiliar objects when compared to the apparatus alone. Species differences emerged with longer gaze durations exhibited by belugas and bottlenose dolphins and significantly shorter gaze durations for Pacific white-sided dolphins. It is likely that the animals categorized objects into familiar and unfamiliar categories, but the free-swim paradigm in naturalistic social groupings did not elicit clear responses. Rather this procedure emphasized the importance of attention and individual preferences when investigating familiar and unfamiliar objects, which has implications for cognitive research and enrichment use.