Ink-redible Octopuses: Scientists discover new octopus hunting behaviours

In commemoration of World Octopus Day (8 October), our Kaia Initiative member Norman has written about octopus hunting behaviours!

When was the last time you saw an octopus, if ever? Perhaps it was from Finding Nemo, or perhaps an aquarium, or maybe even on a dinner plate. While not commonly seen, I’m sure that many of us have at least heard of this strange-looking creature with 8 tentacles. What many of us may not know is that octopuses are considered some of the most remarkable creatures on the planet, having three hearts and nine brains. Alongside squid and cuttlefish, they fall under the family of cephalopods, characterised by bilateral body symmetry, a prominent head, and a set of arms or tentacles. Their exceptional intelligence rivals that of other famously smart animals like crows and apes, allowing them to complete puzzles, untie knots, and be expert escape artists from aquariums.

These incredible creatures have always been known to be smart, but not so much social. Scientists have generally considered them to be solitary, as they go through life without much octopus interaction except brief mating encounters. However, new research has proven otherwise, highlighting the inter-species relationships that the octopus enjoys.

For decades, octopuses have been seen hunting alongside other fish, but scientists have assumed that these fish were simply leeching off the predatory success of the octopuses, stealing whatever food they could get from them. Yet, a study published on 23rd September 2024 reveals that the truth is far more complex than we believed.

With over 120 hours spent diving and recording video on a camera rig in the Red Sea, Eduardo Sampaio and his colleagues captured 13 separate instances of mixed-species hunting. As the lead study author and an animal behaviourist at the Max Planck Institute, Eduardo and other researchers found the way octopuses and fish hunt together in groups to be surprisingly sophisticated. The fish and octopuses have been found hunting in packs wherein members of different species contributed unique skills to the hunting party. Sometimes the octopuses take charge, and sometimes they follow cues from the fish instead. For instance, the fish, such as the goatfish (Mullidae), performs the search, leading the group to areas of interest, but the big blue octopus (Octopus cyanea) determines when the hunt is on. In some cases, the fish even initiate bouts of hunting, recruiting octopuses from their dens. This relationship is mutually beneficial, as researchers have determined that they have indeed been able to catch more crustaceans, fish and molluscs as a result.

The researchers write, "The [octopuses'] exhibited a range of partner-dependent behavioural flexibility, especially concerning the use of social information when deciding to switch foraging strategies and whom and when to punch, indicates that day octopuses have hallmarks of (heterospecific) social competence and cognition."

The researchers have also captured an amusing phenomenon that we are all too familiar with: the octopuses have “punched” some of the fish with their tentacles, appearing to be disciplining or punishing them. The blacktip groupers are common targets, and it appears to be with good reason as they tend not to contribute much to the hunting pack and instead just loiter opportunistically nearby to feed off the work of the rest of the pack. Yet, they are not always a mere annoyance. These blacktip groupers have been noted to be akin to anchors, holding the group in one place and sending signals that a zone might be worth a closer look. Being ambush predators, their patience in waiting for prey to emerge offers valuable information to the whole group.

"These results broaden our understanding of leadership and sociality, emphasizing the complexity and adaptability of social interactions in nature," Sampaio concludes. Such fascinating discoveries continue to remind us just how much there is left for us to learn about the vast world we live in.

-Norman, 16

References:

1. https://www.nature.com/articles/s41559-024-02525-2

2. https://ocean.si.edu/ocean-life/invertebrates/why-octopus-brain-so-extraordinary

3. https://www.newscientist.com/article/mg24432610-400-octopuses-were-thought-to-be-solitary-until-a-social-species-turned-up/

4. https://www.popsci.com/science/octopus-and-fish-hunt-together/

5. https://www.sciencealert.com/octopuses-team-up-with-fish-to-hunt-and-will-punch-them-if-they-act-up