Researchers now have proof that New Caledonian crows make and use hooked stick tools when hunting for insects.
University of Exeter's Dr. Jolyon Troscianko and University of St. Andrews' Dr. Christian Rutz developed tiny video cameras to observe crows, capturing video recordings showing the bird making and using tools for the first time. Based on their footage, they reported two instances of tool production and use, with one crow taking a minute to make the tool before using it to probe tree crevices and leaf litter for food.
According to Troscianko, the only video footage of tool production and use in crows come from baited feeding sites, where the birds are provided raw materials and given probing tasks by researchers. His work with Rutz, however, is the first close look at crows using tools under natural conditions.
"By documenting their fascinating behavior with this new camera technology, we obtained valuable insights into the importance of tools in their daily search for food," he said.
For the study published in the journal Biology Letters, cameras were attached to the bird's tail feathers. Weighing about the same as a British 2-pound coin, the cameras were fitted with tiny radio beacons that allowed Troscianko and Rutz to recover them once they had been detached from the 10 birds part of their research.
Rutz explained that the cameras stored footage on a microSD card, functioning much like how smartphones today. Aside from convenience, this also helped give the video recordings stunning quality.
At first, the researchers were not able to spot the crows using tools in the footage. It was only after Troscianko went through the video recordings again frame-by-frame that he discovered the bird's behavior. Aside from proof that New Caledonian crows make and use hooked stick tools, however, the video also gave the researchers a glimpse at another behavior exhibited by the bird.
According to Rutz, a crow dropped its tool but recovered it from the ground afterwards shortly, which suggests that tools are valued and not simply discarded after one use. He said this is in line with results from their recent bird experiments, where it was observed that crows hate losing their tools and will resort to various tricks to secure them. Some of the birds have even been seen storing tools in tree holes temporarily, much like how pens are kept in holders.
New Caledonian crows are found in New Caledonia, a South Pacific island.
This study received funding support from the Biotechnology and Biological Sciences Research Council.
Photo: Derek Bakken | Flickr
