A team of researchers just discovered another crow species capable of using tools, the ‘Alalā. The ‘Alalā, or Hawaiian crow, uses sticks as tools without training or prompting. The findings provide new insights into the evolution of tool use in crows. The details are in a paper that was just published in the Nature journal.
There are dozens of crow and raven species. Yet tool use has only been documented in a single species, the New Caledonian crow (Corvus moneduloides). Known for their intelligence and cognitive abilities, the New Caledonian crow is also capable of tool use. The birds use sticks to extract insects from crevices in trees and vegetation. In captivity, they have also passed tests involving more complex tools. Since the New Caledonian crow was the only species known to use tools, the evolutionary origins of the behavior were unknown.
Researchers began investigating other corvids (crows and ravens) to look for signs of tool use. They had noted that New Caledonian crows have unique bills compared to their relatives. Their beaks are straight with the tip angled slightly upwards, a trait believed to be connected to their use of stick tools. The beak shape could help the crows hold a tool straight. The Hawaiian crow (Corvus hawaiiensis), or ‘Alalā, has a similar bill and was the focus of the team’s study. The ‘Alalā is extinct in the wild but there is a captive breeding program with plans for re-release.
The team found that like the New Caledonian crow, Hawaiian crows are also able to use tools. The crows were observed using sticks to get food items. 104 out of 109 (all of the remaining Hawaiian crows) individuals were able to extract bait items using tools without any training or prompts.
Interestingly, the New Caledonian crow is only distantly related to the ‘Alalā. However, the two species live in similar habitats. This may explain how tool use evolved independently in genetically distinct species. The research team’s findings will help scientists explore the evolution of tool use in birds and other animals.
Christian Rutz et al. Discovery of species-wide tool use in the Hawaiian crow. Nature (2016).