An octopus will team up with schools of fish to hunt their shared favourite foods

Embargoed until: Publicly released: 2024-09-24 01:00

International

Eduardo Sampaio and Simon Gingins

While octopuses usually keep to themselves, some will recruit groups of fish to hunt with, according to international researchers who say these cross-species hunting groups have a complicated relationship. The team tracked some of these hunting groups while scuba diving in the Red Sea to try and figure out how they worked - whether octopuses were the leader or if it was more complicated than that. The researchers say after looking at 120 hours of data, it appears leadership of the hunting groups is shared depending on the task, for example, goatfish will decide where a hunting pack moves, while the octopus will then decide whether and when a move is made. These hunting packs are kept well in line, the researchers say, with octopuses seen punching fish in their gang to demote them to the outside of the pack in a move they think helps keep the group under control.

Media release

From: Springer Nature

Ecology: Shared leadership in octopus-fish hunting groups *IMAGES & VIDEO*

Some octopus and fish species appear to share leadership when hunting prey together, according to a Nature Ecology & Evolution paper. The findings broaden our understanding of the sophisticated cross-species social life of octopuses and fish.

Octopuses, which are often considered to be solitary animals, have been observed to hunt in groups with different species of fish — including several species of goatfish and groupers — for shared prey such as molluscs and crustaceans. Previous observations of these groups suggested that the octopus lead the hunt while the fish usually follow. More complex group interactions between octopuses and fish have been suggested, but these are challenging to document.

Eduardo Sampaio and colleagues tracked octopus–fish hunting packs during scuba diving expeditions in the Red Sea. They observed hunting groups consisting of one day octopus and different species of fish, including gold-saddle goatfish and blacktip groupers, totalling 13 groups. After collecting and analysing data from 120 hours of underwater dives, the authors report that leadership is shared among groups for different types of decisions. For example, goatfish specialized in environmental exploration — deciding where the hunting pack moves — while the octopus decided whether and when the move would be made. This joint effort leads to higher hunting success compared to the octopus or fish acting alone, depending on group composition. Sampaio and colleagues also observed aggressive control mechanisms amongst groups members, including fish displacing others by darting towards them and octopuses displacing fish to outer areas of the group by punching them.

The authors note that whilst other types of mixed-species hunting pack are known — such as badger–coyote, mixed birds, and moray eel–grouper groups — they appear to be less behaviourally flexible in using social information to change strategy compared to octopus–fish hunting groups.

Multimedia

An octopus cyanea performing a web-over

An octopus cyanea hunting with a blacktip grouper and a gold-saddle goatfish

An octopus cyanea hunting with a blue goatfish, while a blacktip grouper waits

Examples of octopuses punching fish, thus displacing them

Shared leadership in octopus-fish hunting groups

Typical movement dynamics and web-over temporal characteristics

Typical movement during multispecific group hunting

Journal/
conference: Nature Ecology & Evolution

Research:Paper

Organisation/s: Universidade de Lisboa, Portugal

Funder: We thank the fieldwork assistants, discussions with colleagues in the Department of Collective Behaviour, and all staff of the Inter-University Institute for Marine Sciences (Israel), Open Ocean Sciences Centre (Egypt) and Lizard Island Research Station (Australia) for invaluable assistance during fieldwork seasons. E.S. acknowledges funding from Fundação para a Ciência e Tecnologia (FCT) with a PhD grant (SFRH/ BD/131771/2017) and the MARE strategic project (UID/MAR/04292/2019). Fieldwork was also funded by National Geographic Society (EC-427R-18), PADI Foundation, Malacological Society of London and Animal Behavior Society. V.H.S. acknowledges support from the CRG-CASCB joint grant, funded by the EAS Department, MPI-AB and CASCB at the University of Konstanz. A.S. acknowledges the International Master of Science in Marine Biological Resources (IMBRSea, Ghent University). M.N. acknowledges support from the Hungarian Academy of Sciences, grant 95152 (to the MTA-ELTE ‘Lendület’ Collective Behaviour Research Group), and the National Research Development and Innovation Office under grant no. K128780. A.S.-P. acknowledges support from the Gips-Schüle Stiftung. I.D.C. acknowledges support from the Office of Naval Research (grant number N00014-64019-1-2556), the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement (number 860949), and the Deutsche Forschungsgemeinschaft Gottfried Wilhelm Leibniz Prize 2022 584/22 (I.D.C.) All authors acknowledge support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy-EXC 2117–422037984 (to I.D.C.) and the Max Planck Society.

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