NEW DISCOVERIES ON WRASSES USING TOOLS TO CRACK OPEN PREY
New observations have significantly expanded our understanding of anvil use in wrasses, particularly among South American wrasses, Halichoeres species. This tool-use behavior, in which wrasses use hard surfaces to break open prey, was once thought to be rare and restricted to a few species and locations. However, recent findings from Southern Brazil and the Turks and Caicos Islands indicate that anvil use is far more widespread than previously recorded. Wrasses have been observed using a variety of hard surfaces, including rocks, rubble, and even live conch shells, to crack open crabs, sea urchins, and molluscs, demonstrating remarkable behavioral flexibility.
A key feature of this behavior is its adaptability. Wrasses do not rely on a single anvil or striking point during an event; instead, they are highly opportunistic, shifting between different surfaces as needed. This flexibility enables them to exploit a diverse range of prey and enhances their foraging efficiency. Notably, no strong preference for one side of the body was observed during anvil use, suggesting that wrasses are not lateralized in the same way that tool-using primates often are.
-Sequence of a yellowhead wrasse, Halichoeres garnoti, striking a brittle star arm on rubble by swinging its head from the left to the right
The discovery of anvil use in additional wrasse species suggests that this behavior may be far more widespread than previously believed. To fully grasp the extent of anvil use across various species and regions, further focused research is essential. Controlled experiments offering prey to wrasses could yield valuable insights into the evolution of this behavior, its ecological advantages, and its broader evolutionary significance.
video: A yellowhead wrasse (Halichoeres garnoti) cracking open a brittle star to access the meat inside, using rocks and rubbles, and even a live conch, by C.E. O'Brien
Reference (Open Access): Tariel-Adam et al., 2025 Tool use by New World Halichoeres wrasses. Coral Reefs
