Monocular tool control, eye dominance, and laterality in New Caledonian crows

Area of Science:

• Animal behavior
• Comparative cognition
• Evolutionary biology

Background:

• Tool use is widespread in animals, but morphological adaptations are rare.
• New Caledonian crows (Corvus moneduloides) show advanced tool use, extracting larvae with sticks.
• These crows possess unusually wide binocular visual fields, potentially linked to tool use.

Purpose of the Study:

• Investigate the relationship between visual fields and tool use in New Caledonian crows.
• Determine if eye dominance influences tool laterality in these birds.
• Compare visual-motor coordination in tool use between crows and humans.

Main Methods:

• Observed natural tool extraction behavior in New Caledonian crows.
• Analyzed visual field data and eye dominance.
• Correlated eye preference with tool side preference (laterality).

Main Results:

• Tool tips were viewed monocularly by the contralateral eye during extraction.
• Individual eye dominance significantly predicted tool laterality.
• This contrasts with human species-wide motor laterality.

Conclusions:

• Wide binocular fields in crows may facilitate monocular viewing of tool tips.
• Eye preference, not binocularity, drives tool laterality in New Caledonian crows.
• Differences in visual-motor coordination for tool use exist between crows and humans.