Abstract:
An intricate network of crevices adorns the skin surface of the African bush elephant,
Loxodonta africana. These micrometre-wide channels enhance the effectiveness of thermal
regulation (by water retention) as well as protection against parasites and intense solar
radiation (by mud adherence). While the adaptive value of these structures is well established,
their morphological characterisation and generative mechanism are unknown. Using
microscopy, computed tomography and a custom physics-based lattice model, we show that
African elephant skin channels are fractures of the animal brittle and desquamation-deficient
skin outermost layer. We suggest that the progressive thickening of the hyperkeratinised
stratum corneum causes its fracture due to local bending mechanical stress in the troughs
of a lattice of skin millimetric elevations. The African elephant skin channels are therefore
generated by thickening of a brittle material on a locally-curved substrate rather than by a
canonical tensile cracking process caused by frustrated shrinkage.
