A Day Octopus Collaborates with Blue Goatfish
Recent research reveals that octopuses exhibit a level of sophistication previously underestimated. These generally solitary creatures have been found to collaborate with fish to hunt for prey, demonstrating an ability to distinguish between cooperative and non-cooperative members of their hunting groups.
The study focused on “hunting packs” consisting of one octopus and several fish. In this dynamic, fish scout for potential prey and signal the octopus to flush out targets hidden in crevices that are inaccessible to them.
Interestingly, octopuses will dismiss fish that merely linger around the group without actively participating in the hunt. “They exhibit an understanding of the dynamics of their group,” said a researcher from the Max Planck Institute of Animal Behaviour.
The day octopus (Octopus cyanea) is prevalent across the Indo-Pacific region, with habitats extending from the Red Sea to Hawaii. Their hunting strategy involves wrapping around objects like rocks, creating a ‘bag’ with the membrane between their tentacles to capture small animals, a technique known as web-over.
The concept of hunting groups with a day octopus and various fish species was initially reported in the 1990s. It was previously assumed that fish simply followed the octopus to snatch escaping prey.
During an extensive 120-hour observation in the Red Sea, researchers documented 13 distinct group hunts using a double camera setup to analyze the three-dimensional movements of the participants.
“The findings illustrate that the octopus not only follows the fish, but also responds to their movements as signals for potential prey,” the researcher noted.
If a fish darts towards a location quickly, this action communicates a potential discovery to the group. If ignored, the fish will continue to signal the octopus by swimming back and forth.
Octopuses also alter their hunting techniques when accompanied by fish. While hunting alone, they perform quick, successive web-overs, but in the presence of fish, they execute fewer yet longer web-overs which can last over a minute, particularly after catching prey.
Research identified six fish species commonly forming hunting packs. Notably, blue goatfish (Parupeneus cyclostomus) emerged as the most effective collaborators, actively seeking out prey and guiding the octopus, while blacktip groupers (Epinephelus fasciatus) were the least successful in locating targets.
Octopuses seem to acknowledge this difference in effectiveness. They were recorded punching blue goatfish only three times compared to 27 instances with blacktips. “This suggests a recognition of which species are beneficial for collaboration,” the researcher concluded.
Though it remains unclear if octopuses can remember specific fish from previous hunts, their territorial nature suggests that interactions are likely with the same individuals over time.
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