Small Fish Uses Bigger Fish as Cover to Ambush Prey

A tropical fish species has been observed swimming behind larger fish to hide itself while hunting for prey. This interesting behavior could provide valuable insights into how animals adapt to the potential degradation of coral reefs. Scientists believe that understanding these behaviors can help predict future adaptations of animals in changing environments.

In the Caribbean, divers have noticed the West Atlantic trumpetfish (Aulostomus maculatus) swimming alongside non-predatory fish, such as the stoplight parrotfish (Sparisoma viride). While the trumpetfish doesn’t prey on the parrotfish, swimming close to them allows it to approach its prey without scaring them away, according to Samuel Matchette, a researcher at the University of Cambridge.

To investigate this phenomenon, Matchette and his team conducted experiments to determine whether the damselfish (Stegastes partitus), one of the trumpetfish’s common targets, can be fooled by this technique.

The researchers conducted their experiments in coral reefs near the Caribbean island of Curaçao. They set up tripods connected by a nylon line, allowing them to pull 3D models of dummy fish past colonies of real damselfish.

When a model of a trumpetfish was pulled over the damselfish, the damselfish quickly fled. However, when a model of a parrotfish was pulled over the damselfish, the damselfish continued their normal activities. The interesting observation was when both the trumpetfish and parrotfish models were pulled together, mimicking the swimming behavior of the trumpetfish and parrotfish, the damselfish fled. This suggests that the damselfish are familiar with this tactic used by the trumpetfish. The experiments were repeated on 36 damselfish colonies at multiple locations around the island.

Samuel Matchette explains that this provides strong evidence that the trumpetfish uses other fish as camouflage to approach their prey. This is the first known example of an animal using another animal as a cover. It is similar to human hunters using horses as a cover when approaching birds. Matchette highlights the importance of understanding this behavior as coral reef habitats might change due to rising sea temperatures, becoming less complex and biodiverse. If the reef’s ability to provide cover is diminished, fish species that rely on it may start mimicking the trumpetfish’s behavior as an alternative strategy.

Innes Cuthill, a researcher at the University of Bristol, emphasizes the significance of this research, turning natural observations into scientific experimentation. He explains that the behavior of the trumpetfish swimming closely to parrotfish provides a predatory advantage rather than protection against predators.