The Ecological Significance of Tool Use in New Caledonian Crows

Abstract

Clever Crows Understanding the adaptive significance of animal tool use requires reliable information on the foraging behavior in the wild. New Caledonian crows consume a range of foods and use sticks as tools to extract wood-boring beetle larvae from their burrows. These larvae, with their unusual diet, have a distinct isotopic signature that can be traced after consumption by the crows in the crows' feathers and blood. By comparing the stable isotope profiles of crows' tissues with those of their food sources, Rutz et al. (p. 1523 ) estimated the proportion of larvae in crow diets, providing a proxy for tool-use dependence in individual crows. Just a few larvae can satisfy a crow's daily energy requirements, highlighting the substantial rewards available to competent tool users and their offspring. Thus, tool use provides New Caledonian crows with access to a very nutritional food source that is not easily exploited by beak alone.