As coral reefs become increasingly decimated, predatory fish have fewer places to hide when stalking prey. A new study now suggests they're adapting, by using other fish as mobile hunting blinds. It's the first time the behavior has been documented in a non-human animal.
Scientists from the University of Cambridge started off by questioning scuba divers in the Caribbean about the behavior of local predatory reef fish.
Among other things, it was revealed that the trumpetfish (Aulostomus maculatus) was often seen swimming alongside harmless plant-eating species such as the parrotfish (Sparisoma viride). What's more, the behavior occurred most often on degraded reefs.
Although the reason for this activity was unknown, the scientists suspected that it was a hunting strategy. In order to see if this was the case, Dr. Sam Matchette and PhD student Christian Drerup installed a testing system amidst reefs off the coast of the island Curaçao.
The clothesline-like setup utilized thin nylon lines to pull 3D-printed fish models over colonies of small herbivorous damselfish (Stegastes partitus).
When a lone trumpetfish model passed overhead, the damselfish initially swam up to check it out, then darted away when they realized that it appeared to be one of their chief predators. When a lone parrotfish model was used, they reacted far less, as they didn't see it as a threat.
Importantly, the damselfish also showed little reaction when the trumpetfish model was attached to the parrotfish model, replicating the manner in which real trumpetfish shadow parrotfish and other non-predatory species. It is now believed that this behavior either completely hides the trumpetfish from their prey's view, or at least obscures their appearance so they're not identifiable.
"The shadowing behavior of the trumpetfish appears a useful strategy to improve its hunting success," said Dr. James Herbert-Read, senior author of the study. "We might see this behavior becoming more common in the future as fewer structures on the reef are available for them to hide behind."
A paper on the research was recently published in the journal Current Biology. The testing apparatus can be seen in use, in the video below.
Source: University of Cambridge