Cooperation or dolphin ‘tug-of-war’? Comment on Kuczaj et al.and Eskelinen et al
Stephanie L. King, Simon J. Allen, Richard C. Connor & Kelly Jaakkola
Two recent papers by Kuczaj et al. (2015) and Eskelinen et al. (2016) claim to have demonstrated that (i) bottlenose dolphins (Tursiops truncatus) cooperated to solve a novel task and, (ii) vocal signals were important for coordinating these cooperative efforts. Although it is likely that bottlenose dolphins may share communicative signals in order to achieve a common goal, we suggest that this has not been demonstrated in the aforementioned studies. Here, we discuss the two main problems that preclude any definitive conclusions being drawn on cooperative task success and vocal communication from these studies. The first lies in the experimental design. The ‘cooperative task’, involving an apparatus that requires two dolphins to pull in opposite directions in order to achieve a food reward, is not conducive to cooperation, but could instead reflect a competitive ‘tug-of-war’. It is therefore of questionable use in distinguishing competitive from cooperative interactions. Second, the suggestion that the occurrence of burst-pulsed signals in this task was indicative of cooperation is disputable, as (i) this study could not determine which dolphins were actually producing the signals, and (ii) this sound-type is more commonly associated with aggressive signalling in dolphins. We commend the authors for investigating this exciting and topical area in animal communication and cognition, but the question of whether dolphins cooperate and communicate to solve a cooperative task remains as yet unanswered.