FUR STRUCTURE, THERMAL PROTECTIVE PROPERTIES, AND MOULTING IN THE EUROPEAN MOLE (TALPA EUROPAEA L.)

Abstract

A detailed study of the structure of fur, its thermal conductivity and hair histological composition using 68 European mole pelts revealed some adaptive features of the fur associated with the burrowing lifestyle. Mole fur is relatively short, even, and thick. Segments of the hair shaft resemble a spring, allowing the mole to move freely in narrow tunnels, both forwards and backwards. Down hair is highly homogeneous (equatorial type), pelage is evenly distributed over the body, and hairs of different categories are of approximately the same size. European mole hairs are noted for the medulla which is poorly developed compared to the stronger cortex. This structure enhances the mechanical and thermal insulation properties of the animals’ pelage. Mole fur is divided into four categories of hairs: guard hairs, level I and II awn hairs, and down hairs. Guard hairs are slightly curved, springy, rising above the other layers, mainly performing the tactile sensation and support functions. Awn hairs are pleated in the form of a stretchedout concertina, distinctly segmented, with a strong hair shield region, serving to forming and maintain pelage integrity. Down hairs are segmented, wavy, thin, with extremely narrow and short hair shield region. The underfur performs an important thermal insulation function. A hair shaft consists of three layers of cells: cuticle, cortex and medulla. Their microstructure is species-specific and can be used both for species diagnosis and in taxonomy. Despite affluent greasing, very high strength of the hair, and its ability to bend and recline in any direction, mole fur quickly gets worn out from constant contact with the soil. Fur recovery is achieved through special compensatory moulting – an important adaptive feature found only in true underground mammals. There are two full-scope seasonal moults in spring and autumn, each following its specific pattern. The autumn moult starts from the rump and the back, moving towards to the head and the sides, and ending on the belly and the neck underside. The spring moult, on the contrary, begins on the back and the belly, then gradually involves the head and the scruff, and ends on the rump.