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LIKKIN' LIZERDS

Chameleon Senses

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Chameleons prefer to LICK the dew off of leaves over drinking still water. They have been known to lick the branches, or to be more accurate, taste test the branch with their tongue to determine if the territory is occupied. A male chameleon will rub its cloaca (vent) on branches after defecating, it is thought to mark their territory. This "taste test" or smelling of the branch is a substitution for their inability to smell. Their Jacobson's organ, located in the mouth of most reptiles, (used to "smell" particles picked up by the tongue) is virtually non-functioning, however, taste buds have been found in their tongues. Very little research has been done on this because it is considered to be an unimportant issue. I think there must be something important about taste to the chameleons. They tend to reject the same foods after a while, and seem to get excited about others.

See Myths -Tongue

literature cited (,2,4,5,6,7,9)

HEARING

Chameleons have very limited hearing, tuning in to frequencies between 200 and 600 Hz as compared to most other lizards from 100 to 4000 Hz, and to humans 20 to 20,000 Hz. Most snakes can pick up sound waves between 100 to 700 Hz.

Chameleons ears have degenerated over time, are covered with scales, and possess no eardrums.

Female C. Oweni, and C. Johnstoni are known to produce low purring sounds when being handled by humans or approached by males of their species. Male veiled chameleons have been recorded (see LINKS PAGE - interesting sites to hear this) "hooting" during the pre-mating rituals.

literature cited (2,4,5,6,7,8,9,11)

SIGHT

Chameleons have one of the most sophisticated eyes in the animal kingdom. They are described as binocular (each eye moves independently of the other) and are probably the chameleon's greatest sense. Combined they provide nearly 360 degree vision without turning the head, and allow the chameleon to see in front of and behind him

When searching for prey, the eyes are constantly moving in independent directions. when the meal is spotted BOTH eyes lock on the target and the tongue ZAPS it (see TONGUE on MYTHS PAGE). When the tongue is released, the eyes are closed for protection from projectile damage. More protection for these irreplaceable assets is exercised when the animal sleeps. Their eyelids close, and the eye rolls down until the pupil is behind a protective bone. Still even more insurance against damage comes in the form of scale covered eye lids. They completely cover the entire eye except for a small opening for the pupil.

The first time a chameleon is observed cleaning its eye can cause great stress to the chameleon owner. It appears that their eye is about to pop out of the socket. They will "blow up" their eye turret and rub it on something to clean it or to knock off loose skin during shedding.

NEGATIVELY POWERED LENS IN THE CHAMELEON'S EYES

According to a paper published in the 23 February 1995 issue of Nature, research done by Matthias Ott and Frank Schaeffel of the University Eye Hospital, Department of Experimental Ophthalmology in Tubingen, Germany has shown that chameleon's eyes have a negatively powered lens. This negatively powered lens gives the chameleon a fast-focus telephoto eye that can judge distance much like a reflex camera, unlike other vertebrates whose eyes must triangulate on an object using binocular vision to get a distance bearing. In the paper, Ott and Schaeffel also show that the image that forms on the retina of the chameleon is 15% larger than it would be for other vertebrates. The following is the introduction of the published paper.

Chameleons are arboreal lizards that spot their prey visually and catch it by highly precise shots with their long sticky tongue. They scan their environment by large-amplitude independent saccadic eye movements; once an insect is detected, the head axis is aligned towards the target (head tracking), both eyes come forward to fixate the insect and, in a phase called 'initial protrusion', the sticky tongue is loaded with tension by a special hyoid apparatus and subsequently shot out of the mouth with great precision. Lenses placed in front of the eyes produce predictable errors in distance estimation, suggesting that chameleons rely on accommodation cues when measuring the distance to their prey, but focusing has never been measured directly. Using a new technique to measure accommodation, we now show that accommodation is precise enough to serve as the major distance cue. Because accurate focusing requires large retinal images, we have tested image magnification and found that it is higher than in any other vertebrate eye scaled to the same size. This is a result of a unique optical design: unlike other vertebrate eyes, the crystalline lens of the chameleon has negative refractive power. Although there is a trend among vertebrates to increase corneal power and to decrease lens power with higher visual acuity, only in the chameleon eye has this tendency led to a reversal of the sign of the power of the lens.

literature cited (2,4,5,6,7,9,11,12)

SMELL

As was mentioned above, chameleons have a very limited sense of smell. Their Jacobson's organ, located in the mouth of most reptiles, (used to "smell" particles picked up by the tongue) is virtually non-functioning.

literature cited (2,4,5,6,7,9)

TOUCH

(the tail)

A chameleons tail is descried as PREHENSILE, or adapted for gripping or climbing, and that it is. it is almost like a fifth arm/leg, extremely strong, and generally longer than the head and body. The only drawback is it is not regenerative as with the anoles or

(the feet)

Another amazing feature of chameleons is their feet, described as forceps like they have five toes on each foot, fused together in opposing groups of two and three forming pincers. They have three toes inward on the front feet and two toes inward on the rear (known as ZYGODACTYLOUS). These feet have sharp claws and extremely strong grips.

(general)

Experts consider the areas most sensitive to touch to be the corners of the mouth, along the spinal column, and the tip of the tail.

literature cited (2,4,5,6,7,9)

COMMUNICATION

not really a "sense" but requires use of the senses

Pacing or scratching at the front of a cage by the chameleon is... they are asking to get out. They are uncomfortable for some reason (lighting, temperature, humidity)... maybe they just want to go on a "walkabout". You should let them out and check those conditions important to them. If it is an all glass enclosure this could also be related to a lack of good air circulation. Another drawback to glass cages is chameleons do not understand reflections and stress easily when they see their own and perceive it as "another chameleon" ( talk about being afraid of your own shadow ).

Head bobbing is used to claim territory. If the cham sees another cham in the area they may start bobbing their head. This is also practiced before mating. The colors are a good indicator of reason, vivid colors are shown if it is being done as a part of mating.

Gaping mouth with dark colors and hissing... beware of "watchcham" they're angry about something.

Gaping mouth with pale colors is a sign of over heating. coo the cage and cham with a good misting and adjust lighting if necessary.

Closing the eyes for long periods of time during the day... SIGN OF ILLNESS. Get this cham checked out by a good herp vet before it is too late. See ARAV Website if you don't know one

Bright vivid colors without dark spots... contentment or excitement.

Pale colors, tail coiled, jaw resting... relaxed cham - sleeping

literature cited (2,4,5,6,7,9,11)

Chameleons disclose talent for weightlifting

Hunting other lizards: Changing color in 10 seconds is not their only trick

Adam Lusher

The Sunday Telegraph

The chameleon's repertoire of tricks does not stop at changing color, scientists have discovered. It has now also been classified as the only animal in the world with the high-speed reflexes needed to twist its tongue into a deadly suction pad capable of catching prey that an ordinary reptile could never hope to hold.

A chameleon weighing 43 grams can perform feats equivalent to a man picking up a nine kilogram sack of potatoes with his tongue.

This hitherto secret maneuver, over in the blink of an eye, gives chameleons a considerable advantage over other reptiles that rely merely on a sticky tongue to ensnare their prey.

The secret was discovered after researchers at Northern Arizona University became suspicious when relatively large lizards disappeared from a cage they shared with chameleons.

"We realized the chameleons must have been picking off the other lizards in the cage," said Jay Meyers, one of the research team.

"It shouldn't have been happening. How could something with just a sticky tongue catch something so large?

"We decided to get a high-speed video camera and find out."

The camera, shooting at 250 frames a second, caught the chameleons contorting the tips of their tongues milliseconds before impact. The tip would then form a suction seal around the target, exerting such force that the prey was helpless to resist being dragged into the chameleon's mouth.

"It was an amazing display of control and speed," Meyers said. "The seal looks a bit like a baseball glove, with the prey as the ball. Once the seal is formed it acts a bit like the suction cup at the tip of a child's toy arrow and pulls the prey back. The whole thing happens really quickly. It only takes about half a second for the chameleon to shoot its tongue out almost six inches, form a seal around the prey and drag it back to its mouth."

Meyers, who worked with Anthony Herrel, an evolutionary biologist at the University of Antwerp in Belgium, believes that the maneuver involves a pair of muscles on either side of the chameleon's tongue working to roll the tip inwards.

It seems vital to the hunting success of all the species of chameleons (Chamaeleo) they studied.

When small cuts were made in the nerves controlling the muscles making the suction pad, the chameleons' tongues just knocked harmlessly against their prey instead of grabbing it.

Fortunately for the chameleons, their vital nerves grew back.

The hunting trick now seems likely to rank with the chameleon's ability to change color in the space of 10 seconds in response to their mood changes or the need for camouflage.

"It's pretty wild," said Meyers. "You don't even see any other living lizards doing anything close. This is a unique thing for lizards, and probably vertebrates in general. We have seen nothing else that does it. It's unknown elsewhere in the animal kingdom."