Mechanical behaviour of snake skin

Forty-nine samples of skin from the mid-ventral, ventrolateral and mid-dorsal regions of six species of snakes were mechanically tested in uniaxial extension at 0.05 strain/sec. The species of snakes studied ranged from generalists to specialists for arboreal or aquatic habitats. Analysis of the loading curves revealed substantial variation in loads and maximum stiffnesses among samples from different dorsoventral regions within an individual and among homologous samples from different species. Skin thickness varied by a factor of more than five, but this only partially accounts for the differences in the force per width of sample at a given extension. Qualitative differences in the dermal collagen fibres are implied by the shapes of the loading curves and the terminal elastic modulus which varied from about 15 to 585 MN/m2. The strain at beginning of failure ranged from 0.12 to 0.60. The size of the scales within a skin sample was not a reliable predictor of the loading behaviour of the sample. Correlations between the mechanical behaviour of skin and specializations in locomotion and associated musculature are discussed.