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Using Hair for Identification

How can hair be used to identify mammals?

Hair is made up of dead cells that do not change in appearance once they are extruded from the skin. This means that hairs will retain their structure and appearance even when detached from the animal pelt. Further, hair is consistent in appearance among members of the same species (i.e the hair from the pelt of one rabbit will look the same as hair from the same place in the pelt of all rabbits).

A consequence of the above is that hairs collected during field surveys can be examined and compared with hairs from identified animal pelts. The comparison of unknown hair samples with known hair samples forms the basis of hair analysis.

The structure of hair

A hair is made up of a central medulla, surrounded by an outer cortex which may contain pigment granules. The surface, or cuticle, is usually composed of overlapping cuticular scales. Figure 1 shows the basic structure of hair. 

 

Diagnostic characteristics of hair

Although hair of all species has a similar composition, the appearance of the hair can differ between species. It is possible to construct diagnostic keys to identify species based on the differences in appearance of their hair.

The database in Hair ID is a relational database constructed from the diagnostic keys used to identify mammalian hair. This means that by completing a Search Key it is possible to use Hair ID to identify animals from samples of hair.

The diagnostic characteristics of hair that are useful for identification are:

  1. The general profile of the hair.  This includes the length, diameter, color and degree of wave. Figure 1 shows some typical hair profiles, including that of the rabbit.

    A shows a straight hair with a shield region.
    B shows a hair with an flattened and enlarged shield tip
    C shows a wavy underhair
    D shows a close-up of a constriction, which is a slight narrowing of a hair.
  2. The shape of the medulla.  The central medulla of hair is a hollow space filled with shrunken cells and air. The pattern of arrangement of the cells and air spaces can be observed by viewing the hair in whole mount, and used to identify the animal. Figure 2 shows the medulla of the rabbit (Oryctolagus cuniculus)


  3. The shape and appearance of the cross-section. Hairs from different species differ in their cross-section shape. Some are round, while others may be oval, eye shaped, or other identifiable pattern.  Figure 3 shows the cross-section of hair from the rabbit (Oryctolagus cuniculus).



  4. The pattern of scale on the hair surface. The pattern of the scales on the surface of the hair can sometimes be useful in identifying the species. Figure 5 shows the scale pattern of hair from the rabbit (Oryctolagus cuniculus).

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