Crows are surprisingly intelligent and amazing creatures.
New Caledonian crows are the only species besides humans known to manufacture hooked tools in the wild. Birds produce these remarkable tools from the side branches of certain plants, carefully ‘crafting’ a crochet-like hook that can be used for snagging insect prey.
The study, published in Current Biology today (7 December), reveals how crows manage to fashion particularly efficient tools, with well-defined ‘deep’ hooks.
The hook is widely regarded as one of humankind’s most important innovations, with skilful reshaping, a useless piece of raw material is transformed into a powerful tool. While our ancestors started making stone tools over 3 million years ago, hooks are a surprisingly recent advance — the oldest known fish hooks are just 23,000 years old.
Project leader Professor Christian Rutz, from the School of Biology, has conducted field research on New Caledonian crows for over a decade. His team recently noticed that crows’ hooked tools vary considerably in size and shape. While some tools only exhibit a small extension at the tip, others have immaculate hooks.
Professor Rutz explains: “We suspected that tools with pronounced hooks are more efficient, and were able to confirm this in controlled experiments with wild-caught crows. The deeper the hook, the faster birds winkled bait from holes in wooden logs.”
This finding raised the intriguing question of what it takes to make such well-formed hooks. The researchers started planning their study by imagining how humans would approach a comparable task. “When a craftsperson carves a tool from a piece of wood, two things ensure a quality product: good raw materials and skill,” Professor Rutz said.