Video: A trumpetfish accompanies a parrotfish through the coral reef. © Sam Matchette
Mobile hiding on the hunt: trumpet fish use harmless reef dwellers as a privacy screen so that they can stalk their prey undetected, researchers report. They were able to prove this hunting strategy through experiments with fish dummies in a coral reef. It’s an interesting example of the ingenuity of predator-prey competition in the animal kingdom, say the scientists.
Remaining undetected – this strategy is widespread in the animal world, both among the hunters and the hunted: prey animals use various methods to avoid hungry looks. But the robbers also use strategies to avoid being discovered by their victims. In addition to camouflage methods, “playing hide and seek” is also often used: many predators lurk behind trees, rocks and the like for prey in order to deny them the opportunity to escape in good time. However, the use of mobile objects as privacy screens was previously only known from humans: hunters can hide behind mobile animal dummies in order to stalk game. But now the researchers led by Sam Matchette from the University of Cambridge have documented a similar concept in a predatory reef dweller: the trumpetfish (Aulostomus maculatus), which hunts for smaller fish in the coral reefs of the Caribbean.
Why the accompanying swim?
Observations by divers provided the impetus for the study: trumpet fish are sometimes found in close association with parrot fish and other harmless reef dwellers in the coral gardens. So far, however, it has remained unclear what this synchronized swimming is all about. Through their experiments, the scientists now investigated the suspicion that the trumpet fish avoid scaring their prey by their behavior. These include small damselfish that live in groups on the seabed.
In their experiments in the coral reefs off the Caribbean island of Curaçao, the researchers used 3D-printed models of fish. First, a dummy trumpet fish was used, which was pulled past colonies of damselfish on nylon lines. The evaluation of video recordings of the reactions of the fish to the simulated predatory fish documented: they apparently recognized the characteristics of the hunter and quickly fled to their hiding places on the bottom. When the researchers passed the model of a parrotfish for comparison, the damsel fish remained relaxed: the shape of the harmless algae eater apparently did not frighten them. “I was surprised that the damselfish responded so significantly differently,” says Matchette.
Duos do not trigger escape behavior
In the main experiment, the researchers then pulled the two models together across the “stage” to simulate the trumpet fish swimming alongside it in the shadow of the parrot fish. Although this could not always completely obscure the slender predator from the damselfish’s view, the duo did not cause any escape reactions, the scientists found. “When a trumpetfish swims close to another species of fish, it can be visible, but it doesn’t seem to be recognized as a predator because the shape looks different,” Matchette explains. As the team sums up, the study now provides experimental evidence that the trumpet fish actually uses the accompanying behavior so that its prey cannot escape to safety from it at an early stage.
According to the researchers, this explanation also fits in with the fact that the behavior was observed particularly frequently in reef areas where there are comparatively few natural hiding places – for example due to the lack of dense coral structures. Finally, they also focus on a rather sad and cautionary aspect of the story: The importance of hiding by accompanying swimming could become increasingly important for the trumpet fish due to the destruction of coral reefs due to global warming, pollution and overfishing. “Because in the future there will probably be fewer and fewer structures on the reef for them to hide behind,” says senior author James Herbert-Read from the University of Cambridge.
Source: University of Cambridge, professional article: Current Biology, doi: 10.1016/j.cub.2023.05.075