Octopuses cooperate with fish to hunt

Octopuses, which are traditionally solitary, have been found by researchers to exhibit complex cooperative hunting behaviors with fish, demonstrating leadership and collective activity.

New research published on September 23 in the journal Nature Ecology & Evolution details how octopuses and many fish species work together to hunt successfully as a group for mollusks and crustaceans, with each species taking on a specialized role to maximize overall success.

Daytime octopus hunts with black striped grouper and yellow mullet. (Photo: Eduardo Sampaio & Simon Gingins)

Eduardo Sampaio and colleagues conducted several diving expeditions in the Red Sea, tracking and observing 13 predatory groups, including a day octopus ( Octopus cyanea ) and several species of fish such as mullet, grouper and grouper . "We were surprised that these predatory groups could be so sophisticated ," Sampaio said.

Diurnal octopuses are common on tropical reefs from Hawaii to East Africa and can grow to nearly a meter long, according to the Monterey Bay Aquarium. They get their name from their diurnal hunting habits , which are unusual since most octopuses hunt at night. When they catch prey like crabs and clams, they kill them with venom secreted from their salivary glands, then break open the shell with their sharp beak. Diurnal octopuses are quick learners. They live only about a year, and they reproduce only once in their lifetime.

By tracking the three-dimensional movements of the hunting group over 120 hours of footage, researchers found that the dynamics within the group were much more complex than previously thought. They had assumed that the octopus led the hunt, but the study revealed that leadership was shared across species, with different animals contributing their own unique skills to the group.

The fish, especially the smelt, are responsible for exploring the environment . Based on their sensory abilities, they decide where the group should go. Meanwhile, the octopus determines whether and when the group should proceed to the next step, using its intelligence and dexterity to benefit from the fish's findings. According to the researchers, this shared decision-making reflects a new understanding of leadership in multispecies groups, where both stimulation and inhibition of movement can shape group behavior.

The team looked at how group composition affected the behavior of each species. For example, some fish species would spend more effort leading the group when working with octopuses. This cooperation also triggered a 'partner control mechanism,' in which the octopuses sometimes punched the fish to put them in position or to show dominance. Despite these fierce moments, the group functioned effectively, increasing the chances of a successful hunt compared to when the octopus or fish hunted alone.

Another important detail about the octopus' brutal punches is that they are one-sided, meaning the fish never tries to push its partner out of the group because the fish needs the octopus to herd its prey out of nooks and crannies.

The newly discovered behavior challenges the traditional view of octopuses as solitary and asocial. The study demonstrates that octopuses can cooperate with other species, showing signs of social competence and cognitive flexibility. Octopuses adjust their actions based on the behavior of their partners, demonstrating unprecedented social intelligence in the species.