A chemical commonly used in plastic manufacturing may be quietly reshaping predator–prey relationships in the ocean. A new study published in the Journal of Experimental Marine Biology and Ecology has found that oleamide — a lubricant added to plastics such as polyethylene and polypropylene — can alter how the common South Florida octopus (Octopus vulgaris) interacts with its crustacean prey.

Oleamide is widely used to reduce friction during plastic production. However, as plastic products degrade in marine environments, the compound can leach into surrounding waters. This poses a potential threat to marine species, many of which naturally produce biological forms of oleamide as chemical signals.

In marine ecosystems, chemical communication plays a crucial role. Many species rely on chemical cues to detect food, avoid predators, and coordinate reproduction. The biological form of oleamide functions as a pheromone in some crustaceans, including hermit crabs, and is structurally similar to oleic acid, a compound known to influence reproductive processes in certain marine invertebrates. The presence of industrial oleamide in ocean waters could therefore disrupt these finely tuned signaling systems.

To investigate these effects, researchers conducted controlled laboratory experiments examining interactions between octopuses and four prey types: hermit crabs, free-living crabs, snails, and clams. In aquarium settings, octopuses were observed during 90-minute recording sessions, with their proximity to prey monitored every 30 seconds. Feeding behavior was also tracked over 24-hour periods. Altogether, more than 30,000 predator–prey interactions were recorded.

Before oleamide was introduced into the aquariums, the octopuses displayed a clear preference for crustaceans, particularly hermit crabs and free-living crabs. After exposure to the chemical, however, that preference shifted dramatically. Hermit crabs, once a favored prey, became almost as unpopular as snails, which had previously been among the least selected options.

At the same time, overall interaction rates increased. Octopuses made more approaches and grasping attempts toward prey following oleamide exposure. Yet despite this rise in contact, total prey consumption did not increase. Instead, many interactions were categorized as non-consumptive — instances where the predator grasped prey but did not eat it.

The behavior of prey species also changed significantly. Crustaceans exposed to oleamide reduced their predator-avoidance responses, even as octopuses became more exploratory and increased physical contact. Under normal circumstances, increased predator activity would be expected to trigger heightened defensive behaviors. In the presence of oleamide, however, this adaptive response appeared to weaken.

Researchers suggest that crustaceans may misinterpret industrial oleamide as a natural chemical cue associated with foraging or other benign activities. If so, the compound could encourage prey species to remain active and exploratory rather than retreating from potential danger. Alternatively, oleamide may interfere directly with their ability to detect or process chemical signals related to predation risk.

The fact that octopuses did not increase overall consumption despite more frequent interactions points to another possible effect. Oleamide may disrupt the chemical cues octopuses use to efficiently identify and capture prey, potentially affecting their hunting precision or motor responses. The rise in non-consumptive encounters could reflect confusion or repeated attempts to assess prey in an altered sensory environment.

Notably, some behavioral changes occurred immediately after oleamide was added and persisted for more than 72 hours. This suggests that even short-term exposure to plastic-derived chemicals could have lasting effects on marine animal behavior.

While the study was conducted in laboratory conditions, the findings raise broader ecological concerns. Predator–prey interactions are foundational to marine food webs. Subtle shifts in feeding preferences, defensive behaviors, and interaction rates can cascade through ecosystems, influencing species abundance, resource distribution, and overall community structure.

If similar disruptions occur in natural marine environments where plastic pollution is widespread, oleamide and other chemical additives could contribute to changes in coastal ecosystem dynamics. As plastics continue to fragment and release chemical compounds into the ocean, researchers warn that the ecological consequences may extend far beyond visible debris.

The study highlights the need to consider not only the physical impacts of plastic pollution but also the behavioral and biochemical effects of the compounds embedded within it — effects that may be quietly reshaping life beneath the waves.