Chameleons Change Color to Get the Girl

By Deborah • January 29, 2008

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Contrary to popular belief, the notion that chameleons alter their skin color to disguise themselves and blend in with their surroundings was overturned today — the madcap reptiles are actually behaving flamboyantly to impress the opposite sex and their rivals.

Photo Getty

The new study published in the journal PLoS Biology reveals the need to swiftly signal to other chameleons by being flashy has driven the evolution of their color change trait, contradicting the camouflage theory.

The research illustrates that the dramatic color changes of the South African dwarf are modified to aggressively display to competitors and to seduce potential mates. The study was lead by Dr. Devi Stuart-Fox at the University of Melbourne and Adnan Moussalli University of KwaZulu Natal, South Africa,

Given that these signals are quick — chameleons can change color in a nanosecond — the animal can afford to manifest them noticeably, as the risk that a predator will detect them is limited.

This finding denotes that the evolution of color change serves to make chameleons more eye catching — the complete opposite of the camouflage hypothesis.

Photo Mike1727

The researchers assessed color change by setting up chameleon ‘duels’ — placing 2 males on a branch opposite each other and measuring the color variation.

“If a male is challenged by another male they both begin by showing their brightest colours — until one figures out the other is going to win and changes to a submissive, dark, ‘don’t beat me up colour’.” said Dr Stuart-Fox.

The team demonstrated that dramatic change in appearance is consistently associated with the use of color change as a social signal to other chameleons. The degree of change is not predicted by the amount of color variation in the chameleons’ habitat, as would be expected if chameleons had evolved such remarkable abilities in order to blend in.

About Chameleons
Chameleons are squamates that belong to one of the best-known lizard families. The name chameleon means ‘Earth lion’ or ‘crawling lion.’

Photo True Bavarian

Change of Color
All chameleon species are capable of changing their skin color which can act as an expression of their physical and physiological condition, and also plays a part in communication. Despite popular belief, chameleons cannot change color to their surroundings — they’re naturally colored for their surroundings as a camouflage.

Various chameleon species are able to change different colors including pink, blue, red, orange, green, black, brown and yellow.

Mediterranean Chameleon turned black when it was frightened by dogs.
Photo Rickjpelleg

Chameleons have specialized cells — called chromatophores — that lie in layers under their transparent outer skin. The cells in the upper layer contain yellow and red pigments. Below these is another layer of cells — called iridophores — which contain the colorless crystalline substance guanine. These reflect, among others, the blue part of incident light. If the upper layer of chromatophores appears mainly yellow, the reflected light becomes green.

A layer of dark melanin containing melanophores is situated even deeper under the reflective iridophores. The melanophores influence the ‘lightness’ of the reflected light. All these pigment cells can rapidly relocate their pigments, thus manipulating the color of the chameleon.

Make-up
Chameleons vary significantly in size and body structure, with total length from 1 inch (2.5 centimeters) to 31 inches (79 centimeters). One species thought to be unique to Malawi’s Mount Mulanje is 0.6 inches (1 centimeter) across when fully grown.

Many have head or facial ornamentation, such as nasal protrusions or horn-like projections such as the Chamaeleo Jacksonii, or large crests on top of their head, like Chamaeleo Calyptratus. Males are typically ornamented a great deal more than female chameleons.

Photo Adrian Pingstone

The 5 toes are fused into a group of 2 and a group of 3, giving the foot a tong-like appearance which allow them to grip tightly to narrow branches. Each toe is equipped with a sharp claw to gain traction on surfaces when climbing.

Chameleons have a long tail that’s able to curl up, used almost like a fifth leg to balance on tree limbs etc. and at times used as a weapon.

Their eyes are most distinctive — the upper and lower eyelids are joined, with only a pinhole large enough for the pupil to see through. They can rotate and focus separately to observe two different objects simultaneously, which in effect gives them a full 360 degree arc of vision. Both eyes can focus in the same direction on prey, giving sharp stereoscopic vision and depth perception.

Like snakes, chameleons don’t have an outer or a middle ear which suggests they might be deaf, although snakes can hear using a bone called the quadrate to transmit sound to the inner ear. Some or maybe all chameleons can communicate via vibrations that travel through solid material like branches.

Chameleons have very long tongues — sometimes longer than their own body length — which they can rapidly extend from the mouth faster than human eyes can follow, at around 26 body lengths per second. The tongue hits the prey in about 30 thousandths of a second.

The tongue has a sticky tip on the end, which serves to snare their prey. The tongue’s tip is a bulbous ball of muscle, and as it hits its prey, it rapidly forms a small suction cup. Once the tongue sticks to the prey, it’s drawn quickly back into the mouth, where the chameleon’s strong jaws crush and devour it. Even a small chameleon is capable of eating a large locust or mantis.

Chameleons exposed to ultraviolet light show increased social behavior and activity levels, are more inclined to bask and feed and are also more likely to reproduce as it has a positive effect on the pineal gland.

Kameleon-Chameleon