ParrotsTouchFeel

HERBST CORPUSCLES:

Sensations in Beaking and Tonguing

by Gail Larvenz                                                                                                        
 

Reach Out and Touch Something

    How many times have you handed your companion parrot a piece of broccoli, carrot, cheese or bite of some other new “good-for-him” food, only to in have him take it in his beak but immediately drop it to the floor? How many times have you said to your bird: “How do you know you If don’t like it? You never even tasted it!” As it turns out, he may have actually “tasted” it, just in a different way than we usually think about. I was surprised to learn that, just by touching the “offending food” item with their beaks and tongues, parrots are able to discern an amazing amount of information about the food - or any other object, by means of special sensors located in their tongues and mouths. 

Explaining Corpuscles 
    Without going into a lot of mile-long words or a lesson in histology, or more definitively, avian neuro-anatomy and all off the dry language that goes with it, for the purposes of this article we will just call these special sensory devices “corpuscles. In actuality, they are (and again an oversimplification) special encapsulated nerve endings that are named after the people who discovered them. Some of the names are Pacinian, Kraus, Herbst, Meissner’s and Ruffini. It turns out that reptiles, birds, humans and other mammals. In fact, almost all animals have an a number of these specialized corpuscles located in different parts of the body depending on need. Exteroceptive (meaning capable of receiving stimuli from the outside) encapsulated nerve endings include visual, auditory, touch, pain and temperature endings and record changes in the external environment. Birds have several types of these nerve endings in their tongues and the dermis of their beaks. Corpuscles  in the legs may function as vibration detectors to warn of a predator climbing a parrot’s night time perch.

Information Please 
    These encapsulated nerve endings, or corpuscles, provide our avian friends with information about any object they touch with their beaks or tongues. Most of these corpuscles are tactile or pressure related, others may provide different types of sensory information such as temperature and vibration. If you have ever heard of the “Jacobson’s organ” in the mouths of snakes, you can relate these corpuscles somewhat to that. This organ is a nasal structure which consists of a thin plate of bone that forms the bridge of the nose. It is most developed in snakes and has chemically sensitive nerve endings that respond to a very narrow range of odors. It is present in human embryos but degenerates as the nervous system develops. 

Still a Mystery 
    The exact inner workings of all of these corpuscles is not known, even in human anatomy. It may be that just a touch of the all beak or tongue can tell your parrot an infinite amount of information that helps him decide if an object is familiar as food, something he is interested in playing with or something that does not interest him at all. This may also be why food prepared in one way may be more readily accepted than in another. It may give us a clue as to why birds love seed so much other than the fact that they may love the actual taste. Besides the basic activity, they may derive a lot of enjoyable sensory stimulation from shelling them! There are certainly other parrot behaviors that may be at least partly explained by the highly sensual nature of these corpuscles. Parrots may grind their beaks before they go to sleep at night because the stimulation of these nerve endings in the beak may causes a sensual relaxation and is what is referred to as a “comfort behavior.” Comfort behaviors may have other significant purposes but clearly the reason parrots do them is that they provide a positive sensory experience or simply put, they “feel good.” Bill wiping and beak wrestling are also examples of beak activities that may provide pleasure to birds. The presence of these corpuscles may also provide one more reason for providing a varied diet as parrots may derive great psychological pleasure in manipulating different textures and shapes of food. 

Sensory Stimulation
    One strange example that I have of this “sensory stimulation” involves one of my own birds, Lolli, a 2 year old African grey. Lolli still loves, on occasion, to be fed any kind of vegetable or fruit puree with the pipette that was used when we were hand-feeding her. She gets this special treat once or twice a week. She enjoys the close contact with me but she also plays a “game” with this food. After I pipe the food into her mouth, she squishes it around and somehow manages to work quite a bit of air into it. She works at this until she can get the food to make a “popping” sound, much like the popping of bubble gum. I couldn’t figure out this odd behavior but after observing her for some time, I believe that she derives some strange good feeling from it. She closes her eyes halfway in some sort of hypnotic ‘trance” all the while popping away. I can figure out no other reason for this behavior other than that she is receiving some sort of sensory stimulation from it. At any rate, birds have a lot more “going on” in their mouths than is generally known and as research continues maybe we can find out more about these encapsulated nerve endings. There is definitely more to the avian mouth than meets the eye!


More