The researchers spent hours underwater pulling model fish along a wire past colonies of damselfish, and filming their responses. Credit: Sam Matchette
Key points:
- Researchers used 3D models of fish to test the strange “shadowing” behavior of trumpetfish.
- The team discovered the shadowing is a way to camouflage behind other fish while hunting their prey.
- The strategy may help trumpetfish adapt to the impacts of environmental change.
Divers in the Caribbean Sea often report that trumpetfish swim alongside parrotfish and other reef fish. This strange “shadowing” behavior remained unexplained until a research team diving in the reefs off the coast of Curaçao discovered trumpetfish were in fact concealing themselves while hunting.
In a new study, published in Current Biology, scientists tested if shadowing allowed trumpetfish to approach prey without being detected by pulling 3D-printed fish models past colonies of damselfish, which are a major trumpetfish food source.
When the trumpetfish model moved past alone, damselfish swam up to inspect, and rapidly fled back to shelter in response to the predatory threat. When a model of a herbivorous parrotfish, Sparisoma viride, moved past alone, the damselfish inspected and responded far less. Then, when a trumpetfish model was attached to the side of a parrotfish model to replicate the shadowing behavior of the real trumpetfish, the damselfish responded just as they had to the parrotfish model alone: they did not detect the threat.
These findings confirm that trumpetfish are the only known example of a non-human animal using another animal to conceal itself. This strategy improves hunting success, but also has implications for coral reefs being degraded by climate change, pollution, and overfishing. Hiding behind other moving fish may help animals adapt to the impacts of environmental change.
“The shadowing behavior of the trumpetfish appears a useful strategy to improve its hunting success,” said James Herbert-Read, professor at University of Cambridge. “We might see this behavior becoming more common in the future as few structures on the reef are available for them to hide behind.”