The cat has long whiskers which are sensitive to touch.
Whiskers or vibrissae (/vaɪˈbrɪsi/; singular: vibrissa; /vaɪˈbrɪsə/) are a type of mammalian hair that are typically characterised, anatomically, by their long length, large and well-innervated hair follicle, and by having an identifiable representation in the somatosensory cortex of the brain.[1]
They are specialised for tactile sensing (other types of hair operate as more crude tactile sensors). Vibrissae grow in various places on most mammals, including all primates except humans.[2]
In medicine, the term vibrissae also refers to the thick hairs found inside human nostrils
Vibrissal groups
Vibrissae (derived from the Latin "vibrio" meaning to vibrate) typically grow in groups in different locations on an animal. These groups are relatively well conserved across land mammals, and somewhat less well conserved between land and marine mammals (though commonalities are certainly present). Species-specific differences are also found. Vibrissae of different groups may vary in their anatomical parameters and in their operation, and it is generally assumed that they serve different purposes in accordance with their different locations on the body.
Many land mammals, for example rats[4] and hamsters,[5] have an arrangement of cranial (of the skull) vibrissae that includes the supraorbital (above the eyes), genal (of the cheeks), and mystacial (where a moustache would be) vibrissae, as well as mandibular (of the jaw) vibrissae under the snout.[6] These groups, all of which are visible in the accompanying image of the Patagonian fox, are well conserved across land mammals though anatomical and functional details vary with the animal's lifestyle.
Mystacial vibrissae are generally described as being further divided into two sub-groups: the large macrovibrissae that protrude to the sides and the small microvibrissae below the nostrils that mostly point downwards.[7] Most simply described, macrovibrissae are large, motile and used for spatial sensing, whereas microvibrissae are small, immotile and used for object identification. These two sub-groups can be identified in the accompanying image of the rat, but it can also be seen that there is no clear physical boundary between them. This difficulty in delineating the sub-groups visually is reflected by similarly weak boundaries between them in anatomical and functional parameters, though the distinction is nonetheless referred to ubiquitously in scientific literature and is considered useful in analysis.
Apart from cranial vibrissae, other groups are found elsewhere on the body. Many land mammals, including domestic cats, also have carpal (of the wrist) vibrissae on the underside of the leg just above the paws.[8] Whilst these five major groups (supraorbital, genal, mystacial, mandibular, carpal) are often reported in studies of land mammals, several other groups have been reported more occasionally (for instance, see [9]).
Marine mammals can have substantially different vibrissal arrangements. For instance, cetaceans have lost the vibrissae around the snout and gained vibrissae around their blowholes,[10] whereas every single one of the body hairs of the Florida manatee (see image) may be a vibrissa.[11] Other marine mammals (such as seals and sea-lions) have cranial vibrissal groups that appear to correspond closely to those described for land mammals (see the accompanying image of a seal), although these groups function quite differently.