Operant responding in the Bottlenose dolphin (Tursiops truncatus).
An interesting facet of the analysis of behavior is the manner in which specific operants occur and stabilize in different species. This has been demonstrated in a wide variety of animals from fish to man (Cohen, 1969). While the dolphin has been the subject of a number of fairly exotic investigations, more basic behavioral studies have been neglected. The present study sought to determine the ease with which a dolphin could be trained to press an underwater paddle for fish reinforcers delivered automatically, and if this response could be reliably maintained on intermittent schedules of reinforcement. The subject, a female Tursiops truncatus weighing 105 kg, had been in captivity for approximately 1.5 yr and was estimated to be 4 to 5 yr old. Throughout the period of testing the subject was maintained on its normal ration of 6.9 kg of fish per day. Approximately 2.3 kg of Columbia River smelt (Osmerus sp.) was earned during the daily testing, and an additional 2.3 kg of smelt plus 2.3 kg of Spanish Inackerel (Scomberomorus maculatus) was hand fed at the end of the day. The subject was 19 to 20 hr food deprived at the start of each test session. The subject was housed and tested in a 6 by 6 m floating pen enclosure (Steele, 1970), in Kaneohe Bay, Hawaii. A Davis Scientific Instruments Universal Feeder (Model #320) was mounted at one corner of the pen. During test sessions, a response paddle was mounted on one side of the pen 1.95 in from the feeder and subIllerged to a depth of 0.6 m. A push on the response paddle closed a microswitch that activated both the feeder and a reinforcer tone (700 Hz). The tone reiliained on for the 4 sec required for the feeder to deliver one fish. Responses and reinforcements were recorded on a Rustrac Instruments four-track Event Recorder (Model #309) housed in an adjacent instrument/observation van. The dolphin was trained to approach and press the paddle with the tip of its rostrum in a single training session by reinforcing successive approximations of the response. After shaping, the dolphin was exposed to three reinforcement schedules; continuous reinforcement (CRF) where every response was reinforced, a variable-ratio schedule (VR 6) where reinforcement occurred on the average of every sixth response, and a