New research reveals how collective intelligence helps fish escape predators with greater speed and accuracy.
When a predator strikes underwater, survival depends on quick and accurate decisions. For fish, this means deciding in a split second whether to dive for safety or stay still. Now, a groundbreaking study has shown that larger fish shoals not only react faster—but also make smarter decisions when facing threats.
Published in Science Advances (2025), the research titled “Better and faster decisions by larger fish shoals in the wild” provides the first real-world evidence that animal groups can overcome common trade-offs between speed and accuracy when responding to danger.
🐟 Larger Fish Shoals = Better Survival Strategy
Researchers from Humboldt-Universität zu Berlin and the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), working under the Cluster of Excellence Science of Intelligence (SCIoI), observed wild shoals of sulfur mollies (Poecilia sulphuraria) in their natural habitat: the hot, sulfur-rich waters of the El Azufre River in Tabasco, Mexico.
These small tropical fish live under extreme conditions, constantly exposed to low oxygen, high temperatures, and aerial predators like kingfishers and great kiskadees. Their unique anti-predator behavior—a synchronized group dive—offered scientists a rare look into how collective decisions are made in real time under threat.
🚨 How Do Sulfur Mollies Decide to Dive?
When disturbed, sulfur mollies collectively dive below the surface, creating visible ripples. If the disturbance is a real predator attack, the fish repeat these wave-like dives for minutes. If it’s a false alarm, they stop after the initial response.
This natural behavior allowed scientists to compare reactions to actual predator attacks versus harmless disturbances like birds flying overhead or branches rustling.
🔍 What Did the Study Reveal?
Using data from more than 200 events, researchers found that larger shoals were far more accurate at distinguishing real threats from false alarms. Specifically, larger groups:
- Reacted more quickly to real threats.
- Made fewer mistakes, avoiding unnecessary dives.
- Detected nearly 100% of stealth attacks by predators like the great kiskadee, which flies silently just above the water surface.
💡 Why Bigger Shoals Make Smarter Decisions
In small groups or solo, a fish might dive for every shadow just to be safe—but that wastes energy. Larger shoals, however, can pool information across individuals, making smarter, more balanced decisions. This collective intelligence allows them to optimize both speed and accuracy, a balance typically seen as a trade-off in decision-making.
Lead author Korbinian Pacher explains, “In the largest shoals, decision-making was almost flawless. That level of performance is impossible for a single fish acting alone.”
Senior researcher Jens Krause adds, “This study shows that natural collective cognition is not just a laboratory phenomenon—it exists in the wild where it really counts.”
🤖 From Fish Brains to Artificial Intelligence
The researchers propose that these fish shoals might behave like neural networks or complex self-organized systems, operating near what’s called “criticality”—a state that allows maximum information processing and responsiveness.
This understanding could inspire new models in artificial intelligence (AI) and group behavior prediction, providing insights into how collective systems, including human crowds or robotic swarms, can make optimal decisions.
🧠 What This Means for Science and Evolution
This study not only provides a rare look into the decision-making of wild animal groups but also supports a core idea in evolutionary biology: animals often live in groups to enhance survival through shared intelligence.
By observing real-world examples of fast, accurate group decisions under life-threatening conditions, researchers are gaining a deeper understanding of how intelligence evolves in both natural and artificial systems.
📚 Study Reference
Pacher, K., et al. (2025). Better and faster decisions by larger fish shoals in the wild. Science Advances. DOI: 10.1126/sciadv.adt8600