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Senses

Sight Smell Hearing Touch Taste



Chelonians have very well developed senses, with much of the specialization in the areas of sight and smell.

Sight

Chelonian sight is very well developed. The sea turtles (family: CHELONIIDAE) are able to see well both in water and on land, an adaptation that is very helpful for nesting females.

Along with good sight these animals also possess colour vision. This colour vision is easily demonstrated when looking at the beautiful markings of some species or the way a tortoise will choose what colour food it prefers.

Sight is very important to chelonians for it is one of the first senses used in finding food. A chelonian will be drawn to foods that are green, red, yellow or moving and so depend greatly on their sense of sight.

Smell

Sight shares the dominant spot with smell, which is just as important, if not more, than sight. The olfactory areas of the brain are very well developed and chelonians will almost always sniff for their potential dinners.

Like the squamates, chelonians use their Jacobson's organ to detect faint particles in the air. But, unlike squamates, chelonians are unable to do the tongue flicking motions that are usually associated with this organ, thusly making it hard to figure out how exactly these animals use it.

One proposed idea is that the gular pumping produced by chelonians might pass the air particles over the organ, giving the animal the information it needs.

Chelonians not only use their sense of smell for food, but also during mating and escape. During the mating season the females will produce pheromone chemicals that will tell the males when they are ready to mate. These pheromones are highly addictive once smelled and so some chelonians have made a point of getting to the girl before all the others. Geochelone elongata (the elongate tortoise) during the breeding season the blood flow to the nasal area increases giving these animals the appearance of an irritated nose. In fact the native name for this animals is: "laik nakhonga" which translates to "red nosed tortoise."

Along with mating, smell is also used as a good deterent. Just ask any of the members of the genus Sternotherus or musk turtles. When handled they secrete a very smelly substance out of special glands at the body's surface. Their "musk" is higly potent making them like reptilian skunks.

Hearing

Chelonians, like snakes, lack any external ear opening. But unlike snakes, these animals can still hear air vibrations. Their tympanic membranes are covered by a thin layer of skin that acts as an ear drum allowing the animal's to hear auditory stimuli.

Chelonian hearing isn't as well adapted as that of sight or smell and is mostly geared towards hearing the lower sounds in the frequency range of 100-60 Hz.

Chelonians do make noise, but it is few and far between. Much of the noise can be heard in tortoises in the mating season. The male will usually let loose this low guttural groaning type noise. Sea turtles are also known to make noise. This has been heard when the animals are injured and vocalizations have been consistently heard from Dermochelys coriacea (Leatherback) which has also earned the generic Greek name "sphargis" meaning "to make noise."

Touch

Even though they are clothed in a bony shell, chelonians are quite capable of feeling touch. This is accomplished by thin lines of nerves running all over the shell. These nerves can pick up pressure differences, but (hopefully/luckily) lack pain receptors. So if you were to lightly touch the shell of a turtle, it would feel you doing it.

Taste

While many species do possess taste buds, it is not well known how sensitive they are. Some species like the snapping turtles (Chelydra serpentina) lack taste buds, as do many tortoises. This allows the animals to swallow food that would be considered poisonous or would bite back, without feeling to many ill effects.

Observations of their taste at work can be viewed in captive chelonians, such as those of the genus Terrapene (box turtles) which literally love the taste of strawberries and earthworms (although hopefully not together in the same dish *ick*)



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