Fur elasticity and deformations in the water vole Arvicola terrestris (Rodentia) under the water and in the air

摘要

Thickness of the insulative air layer trapped by fur of swimming animals is significantly related to fur stiffness. Elastic properties of the pelage in the submerged water vole were determined using an original technique capable to control the air layer pressure within the fur simultaneously with measuring the fur local deformations. Fur elasticity is specified by the coefficient K calculated as the ratio of excessive pressure on the pelage to pelage relative deformations produced by the pressure excess. The K values were about 4 X 10~3 Pa. The dry pelage elasticity was 10 times less than that in the submerged fur (K = 2 X 10~2 Pa). The theoretically calculated values were 10 times less if not to take into account possible hair-by-hair coupling. The hair coupling due to surface tension at the boundary area "hairs-water-air" can provide a high elasticity of the pelage necessary to retain air within it in the volume sufficient for reliable heal insulation.