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Testing use of the first multi-partner cognitive enrichment devices by a group of male bottlenose dolphins


Alliance formation plays a crucial part in male dolphins’ lives. These partnerships may last for decades or even for a lifetime; thus, partner choice and the maintenance of these relationships are both considered key components of alliance formation. In our previous investigations, pairs of adult male dolphins showed a high success rate in cooperative manipulation of a cognitive enrichment device. Here, we introduced two novel cognitive enrichment devices to the group of five dolphins, facilitating simultaneous actions for not only pairs, but for three or even four dolphins. The devices were made of PVC tubes, fittings and caps equipped with rope handles, creating a three-way (T-shape) and a four-way (TT-shape) device. The devices were filled with fish and ice and were designed to be opened by simultaneous pull of the handles. Both devices were tested in 12 trials (each lasted for 15 min), separately. Only one of the caps could be opened, the others were affixed with the position of the openable cap counter-balanced over the trials. Although the dolphins received no training regarding the manipulation of the devices, they were successful in cooperatively opening the three-way devices in 10/12 of trials (70% by two and 30% by three dolphins) and the four-way devices also in 10/12 trials (50% by two, 40% by three and 10% by four dolphins). The dolphins interacted with the devices during the entire testing time, and this was mostly spent in cooperative play (77% and 56% of the test duration with the three-way and four-way device, respectively). The majority of the cooperative play was observed between one particular pair of dolphins that was temporarily associated with a third or sometimes even with a fourth dolphin. These findings demonstrate the first successful use of multi-partner cooperative enrichment devices, providing information on the social organization of a male dolphin group.

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We thank the Marine Mammal Department of Ocean Park Hong Kong for their support during our experiment. Special thanks to Dr. Paolo Martelli for his advice and guidance regarding the well-being of the dolphins. Finally, we thank our volunteers, whose help and assistance was invaluable during the execution of the research sessions.


This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. ÁP was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, the ÚNKP-20-5 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation Fund and by the Hungarian Ethology Foundation.

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Correspondence to Eszter Matrai.

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The authors declare that they have no competing interest.

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The project was approved by the Animal Welfare, Ethics and Care Committee of Ocean Park Conservation. Ocean Park gained accreditation from the Association of Zoos and Aquariums (AZA), it is also a member of the World Association of Zoos and Aquariums (WAZA). The animal welfare standards at the Park were also approved by the American Humane Association under its Humane Conservation™.

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Matrai, E., Kwok, S.T., Boos, M. et al. Testing use of the first multi-partner cognitive enrichment devices by a group of male bottlenose dolphins. Anim Cogn 25, 961–973 (2022).

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  • Male alliances
  • Cooperation
  • Cognitive enrichment
  • Cooperative play
  • Indo-Pacific bottlenose dolphin