Pl. VII

Part III · Intelligence in Action · Chapter 7

Social Cognition, Octopolis & Signaling

The octopus's textbook reputation as an antisocial loner has been substantially revised by fieldwork at two remarkable sites in Jervis Bay, New South Wales. Octopolis, discovered in 2009 by diver Matthew Lawrence and philosopher-scientist Peter Godfrey-Smith, formed around a ≈30 cm human-made metal object on an otherwise flat, muddy seabed at ≈15 m; the object seeded a shell midden of discarded scallop (Amusium) valves, and the accumulated shell bed became prime denning substrate for Octopus tetricus (the "gloomy octopus"). Up to 15 animals have been recorded simultaneously. A second, entirely natural site, Octlantis, was documented in 2016–2017 (Scheel et al.) around a few rock outcrops, hosting 10–15 octopuses across ≈23 dens in three clusters over an 18 × 4 m area, with extensive shell middens and no anthropogenic seed object. Crucially, the researchers stress these are aggregations, not "cities" or cooperative constructions: dens arise from individual foraging and maintenance behavior (Scheel et al., Marine and Freshwater Behaviour and Physiology, 2017; Godfrey-Smith & Lawrence, ibid. 2012). The animals cluster because hard substrate for denning is scarce while food is locally abundant—a resource-driven crowding that forces repeated social encounters.

Those encounters are surprisingly structured and communicative. In Scheel, Godfrey-Smith & Lawrence (2016, Current Biology, "Signal Use by Octopuses in Agonistic Interactions"), the team analyzed 186 interactions across ≈7 hours of video. Body coloration functions as an honest agonistic signal: aggressors turn dark (uniformly dark mantle and web), while retreating animals turn pale. The contest logic is strikingly game-theoretic—dark-approaching-dark encounters escalated to grappling, whereas a darkened aggressor facing a paler opponent typically produced retreat by the paler animal, de-escalating the contest before contact. Dominant animals also adopt a conspicuous "stand tall" (or "Nosferatu") display: spreading the arm web, raising the mantle high above the eyes, and darkening—elevating the body silhouette to appear larger, sometimes from a raised position. This is among the clearest evidence that a solitary-lineage invertebrate uses graded visual signals to negotiate dominance rather than simply fighting.

The most attention-grabbing behavior is debris throwing, reported in Godfrey-Smith, Scheel, Chancellor, Linquist & Lawrence (2022, PLOS ONE, "In the line of fire"). Across footage from Octopolis, they scored 102 throws (21 h of 2015 video). The mechanism is distinctive: material (silt, shells, algae) is gathered under the arm web, then the siphon is repositioned under the arms and fired, jetting debris several body-lengths. Seventeen throws struck another octopus. Several lines of evidence hint at targeting rather than mere den-cleaning: throws in social/interactive contexts were more vigorous and biased toward silt (silt hit 42% vs shells 25%); "anomalous" throws launched from an unusual arm position (rather than straight down) hit others 43% vs 13% of the time; high-vigor throws hit 37% vs 8% for low-vigor. Dark-colored (aggressive-state) animals threw with significantly higher vigor (p < 0.0001), tying throwing to the color-signaling system. Females threw far more than males (90 vs 11), and some targets showed anticipatory ducking. The authors remain deliberately cautious about "intent," and a follow-up (Godfrey-Smith et al., 2023, "Octopus toss-up") revisits whether the behavior is truly directed—so intentionality is debated, not settled.

A distinct line of social cognition concerns interspecific cooperative hunting. In the Red Sea and elsewhere, Octopus cyanea (day octopus) hunts alongside reef fish. Sampaio et al. (2021, Ecology) first documented octopuses punching partner fish—a swift arm strike—often to displace competitors or fish that failed to contribute. The landmark follow-up, Sampaio et al. (2024, Nature Ecology & Evolution), used dual-camera 3D field tracking over ≈120 h of footage across 13 hunting groups in Israel, Egypt and Australia. It found genuinely multi-species, functionally differentiated groups: goatfish act as scouts, exploring and setting the group's spatial direction, while the octopus decides if and when the group moves and acts as the principal "influencer," partly by inhibiting others' movement. Leadership is thus distributed and role-specific rather than a simple octopus-on-top hierarchy, with punches serving as partner-control/enforcement to keep exploitative fish (e.g., freeloading species) in line and preserve the octopus's energetic payoff. The work is a rare demonstration of an invertebrate managing a mixed-species social group.

What remains open: whether Octopolis-type sociality is evolutionarily novel behavior or environmentally forced tolerance; whether debris-throwing is intentionally aimed; the fitness consequences (mating, mortality) of aggregation; and how flexible cyanea's partner-control cognition really is.

Striking / counterintuitive:

• A supposedly solitary invertebrate settles disputes with graded color signals: dark = aggressive, pale = submissive, following an almost game-theoretic escalation logic (dark-vs-dark fights; dark-vs-pale ends in retreat).
• Octopuses throw silt and shells using a siphon jet fired from under the arm web, and throws are more vigorous and more likely to hit others in social contexts - one of the only cases of projectile-throwing at conspecifics outside social mammals.
• Females did nearly all the throwing (90 of 101 throws), and dark-bodied (aggressive-state) animals threw hardest (p<0.0001).
• Octopus cyanea punches partner fish to enforce cooperation, and 3D tracking shows leadership is distributed - fish scout and steer while the octopus controls movement timing, not a simple octopus dictatorship.
• Octopolis was seeded by a single human-made metal object; Octlantis proved the phenomenon occurs naturally around rock outcrops too.

Open questions:

• Is debris-throwing genuinely intentional/targeted at specific individuals, or an incidental byproduct of den-cleaning? (Actively debated; Godfrey-Smith et al. 2023 'toss-up' revisits this.)
• Is aggregation an evolved sociality or merely forced tolerance driven by scarce denning substrate plus abundant food?
• What are the fitness consequences (mating success, predation, mortality) of living at high density in Octopolis/Octlantis?
• How cognitively flexible is Octopus cyanea's partner-control - does it represent true social cognition or simpler stimulus-response enforcement?
• Do these social behaviors occur across other octopus species, or are they idiosyncratic to O. tetricus and O. cyanea in specific habitats?

Key researchers/labs: Peter Godfrey-Smith (CUNY / University of Sydney) - philosopher-scientist, co-discoverer of Octopolis, David Scheel (Alaska Pacific University) - lead on signaling and aggregation ecology, Matthew Lawrence - diver, discovered Octopolis in 2009, Stefan Linquist (University of Guelph), Stephanie Chancellor, Eduardo Sampaio (Max Planck Institute of Animal Behavior / University of Konstanz) - octopus-fish collaborative hunting, Simon Gingins, Rui Rosa (University of Lisbon).

Key papers #

• Scheel, D., Godfrey-Smith, P., Lawrence, M. (2016). Signal Use by Octopuses in Agonistic Interactions. Current Biology — First evidence that Octopus tetricus uses dark/pale body color and 'stand tall' posture as graded agonistic signals to settle contests (186 interactions).
• Scheel, D., Chancellor, S., Hing, M., Lawrence, M., Linquist, S., Godfrey-Smith, P. (2017). A second site occupied by Octopus tetricus at high densities, with notes on their ecology and behavior (Octlantis). Marine and Freshwater Behaviour and Physiology — Documented a second, natural high-density aggregation (10-15 octopuses, ≈23 dens), showing Octopolis was not a one-off artifact.
• Godfrey-Smith, P., Scheel, D., Chancellor, S., Linquist, S., Lawrence, M. (2022). In the line of fire: Debris throwing by wild octopuses. PLOS ONE — 102 throws scored; siphon-under-web mechanism; interactive-context throws more vigorous/silt-biased and more likely to hit others, hinting at targeting.
• Sampaio, E., Seco, M.C., Rosa, R., Gingins, S. (2021). Octopuses punch fishes during collaborative interspecific hunting events. Ecology — First documentation of octopuses striking partner fish to control mixed-species hunting groups.
• Sampaio, E., et al. (2024). Multidimensional social influence drives leadership and composition-dependent success in octopus-fish hunting groups. Nature Ecology & Evolution — 3D tracking of 13 groups shows distributed, role-specific leadership: fish scout/steer, octopus decides movement timing and enforces cooperation via punches.
• Scheel, D., Godfrey-Smith, P., Linquist, S., Chancellor, S., Hing, M., Lawrence, M. (2018). Octopus engineering, intentional and inadvertent. Communicative & Integrative Biology — Argues Octopolis/Octlantis shell beds are inadvertent byproducts of individual behavior, not cooperative construction ('not cities').