title: Context-dependent 'safekeeping' of foraging tools in New Caledonian crows.
abstract: Several animal species use tools for foraging, such as sticks to extract embedded arthropods and honey, or stones to crack open nuts and eggs. While providing access to nutritious foods, these behaviours may incur significant costs, such as the time and energy spent searching for, manufacturing and transporting tools. These costs can be reduced by re-using tools, keeping them safe when not needed. We experimentally investigated what New Caledonian crows do with their tools between successive prey extractions, and whether they express tool 'safekeeping' behaviours more often when the costs (foraging at height), or likelihood (handling of demanding prey), of tool loss are high. Birds generally took care of their tools (84% of 176 prey extractions, nine subjects), either trapping them underfoot (74%) or storing them in holes (26%)--behaviours we also observed in the wild (19 cases, four subjects). Moreover, tool-handling behaviour was context-dependent, with subjects: keeping their tools safe significantly more often when foraging at height; and storing tools significantly more often in holes when extracting more demanding prey (under these conditions, foot-trapping proved challenging). In arboreal environments, safekeeping can prevent costly tool losses, removing a potentially important constraint on the evolution of habitual and complex tool behaviour.
authors.affiliation: Centre for Biological Diversity, School of Biology, University of St Andrews, Sir Harold Mitchell Building, St Andrews KY16 9TH, UK bck3@st-andrews.ac.uk.
authors.forename: Barbara C
authors.initials: BC
authors.lastname: Klump
authors.affiliation: Centre for Biological Diversity, School of Biology, University of St Andrews, Sir Harold Mitchell Building, St Andrews KY16 9TH, UK.
authors.forename: Jessica E M
authors.initials: JE
authors.lastname: van der Wal
authors.affiliation: Centre for Biological Diversity, School of Biology, University of St Andrews, Sir Harold Mitchell Building, St Andrews KY16 9TH, UK.
authors.forename: James J H
authors.initials: JJ
authors.lastname: St Clair
authors.affiliation: Centre for Biological Diversity, School of Biology, University of St Andrews, Sir Harold Mitchell Building, St Andrews KY16 9TH, UK christian.rutz@st-andrews.ac.uk.
authors.forename: Christian
authors.initials: C
authors.lastname: Rutz
mesh_terms: D000818:Animals; D005075:Biological Evolution; D046368:Crows / Q000502:physiology*; D005247:Feeding Behavior; D005260:Female; D008297:Male; D053001:Tool Use Behavior
keywords: Corvus moneduloides; corvid; material culture; optimal foraging; tool transportation; tool use