Seasonal differences in the toughness of walnut shells revealed by dropping experiments

Abstract

Carrion Crows Corvus corone drop Manchurian Walnuts Juglans mandshurica onto the ground or allow cars to run over them in order to break them open for consumption. Shell toughness or fragility of walnuts may be an important factor in the choice of strategies. In this study of seasonal differences in the toughness of walnut shells, we dropped walnuts from a high position in both October and December and found that they were more easily broken in December than in October.