Behavioural ecology: Tool manufacture by naive juvenile crows

Abstract

New Caledonian crows (Corvus moneduloides) are the most prolific avian tool-users. Regional variation in the shape of their tools may be the result of cumulative cultural evolution--a phenomenon considered to be a hallmark of human culture. Here we show that hand-raised juvenile New Caledonian crows spontaneously manufacture and use tools, without any contact with adults of their species or any prior demonstration by humans. Our finding is a crucial step towards producing informed models of cultural transmission in this species, and in animals in general.

Social learning in New Caledonian crows

“…In contrast with the results of Kenward et al (2005) and Kenward et al (2006), we found that the development of proficient Pandanus tool manufacture and use in the wild is a very extended process that is comparable to the ontogeny of tool skills in both human and nonhuman primates. Our findings also suggest that social learning plays an important role in that development.…”

“…One 3-month-old crow manufactured a leaf strip and used it as a probe on its first day of exposure to the leaf (Kenward, Weir, Rutz, & Kacelnik, 2005). Kenward et al (2005) and Kenward et al (2006) therefore concluded that basic tool use and basic Pandanus tool manufacture can develop from a disposition to manipulate tool-like material to try and obtain out-ofreach food, without social input. They cautioned, however, that social learning might play a role in the acquisition of "specific techniques and tool shapes.…”

“…Another surprising aspect of Kenward et al's (2005) and Kenward et al's (2006) studies was the short period of time in which the naive hand-raised juveniles learned to use and manufacture tools. All four juveniles were less than 3 months old when they successfully extracted meat with sticks, and by 3 months of age, one subject had manufactured Pandanus tools and used them to extract meat.…”

“…Trial and error has also been suggested to be important in children's obtaining significant knowledge about the physical properties of their tools (Lockman, 2000). Nevertheless, as Kenward et al (2005) pointed out, an important role for trial-anderror learning does not exclude the possibility that either children or NC crows learn important details about manufacture techniques and tool shape culturally. Such social learning might either be a result of direct observation or possibly be acquired less directly via "external memory" located in artifactual material, such as tools and counterparts produced by adults.…”

Preliminary observations of tool-processing behaviour in Hawaiian crowsCorvus hawaiiensis

“…Our preliminary observations have confirmed that ‘Alalā are capable of modifying and manufacturing tools in a variety of ways, paving the way for dedicated experiments that systematically chart the species’ natural tool-making repertoire, as well as its ontogenetic development [4,22–24]. Importantly, subjects need to be tested under conditions where they have access to a wide variety of naturalistic foraging tasks (including those routinely encountered by wild New Caledonian crows [2,3,11,12,16]), and different plant materials for tool manufacture, but not to sticks or other objects that could be used as tools without further processing (as was the case in our first study [4]).…”