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Chameleons, Geckoes and Frogs


Madagascar is home to about half of the world's species of Chameleons. These reptiles are distinguished by their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues and their back-and-forth swaying gait. Many species also possess a prehensile tail, crests or horns on their distinctively shaped heads, and/or the famous ability to change color. They vary greatly in size, their total length ranging from just over an inch for the tiny Brookesia minima, the world's smallest reptile, to over two feet for the male Furcifer oustaleti.

Chameleons' eyes are the most distinctive among the reptiles. 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. This effectively gives them a full 360-degree arc of vision around their body. When prey is located, both eyes can be focused in the same direction, giving sharp stereoscopic vision and depth perception.

Chameleons have very long tongues (sometimes longer than their own body length) which they are capable of rapidly extending out of the mouth. The tongue extends out 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. A bone at the base of the tongue is shot forward to give the tongue the initial momentum it needs to reach the target. A muscular, club-like structure at the tip of the tongue, covered in thick mucus, forms a suction cup. Once the tip sticks to part of the prey, it is drawn quickly back into the mouth, where the chameleon's strong jaws crush the prey. Even a small chameleon is capable of eating a large locust or mantis.

Several chameleon species are able to change their skin colors. Some, such as the Smith's dwarf chameleon, use this ability to blend in with their surroundings, as an effective form of camouflage. Color change is also used as an expression of the physiological condition of the lizard, and as a social indicator to other chameleons. Research suggests that social signaling was the primary driving force behind the evolution of color change, and that camouflage evolved as a secondary advantage. Color change is accomplished using specialized cells that lie in three layers under their transparent outer skin. Cells in the upper layer contain yellow and red pigments while cells below these are colorless and reflect, among others, the blue part of incident light. A third layer of dark melanin-containing cells influences the 'lightness' of the reflected light. All these cells can rapidly relocate the pigments in their cytoplasm, thereby controlling the color of the chameleon.

Uniquely adapted for climbing and visual hunting, Chameleons now inhabit rain forests, savannas and semi-arid regions around the island. They are mostly found in trees or occasionally on smaller bushes, though some smaller species live on the ground under foliage.

Geckos are widespread in Madagascar. These small to moderately large lizards exist in a diverse array of forms across the island, from the neon-colored day geckos to the Uroplatus geckos (also known as leaf-tailed or fringed geckos), masters of camouflage with skin color and color patterns that almost perfectly match tree bark or moss.

Leaf-tailed Geckos, forming the Uroplatus genus, live in the rain forests of the island, and are found nowhere else on Earth. They are nocturnal, and range in length from about 12 inches (U. giganteus) to 4 (U. ebenaui). The larger leaf-tailed geckos spend most of the daylight hours resting vertically, head down, on tree trunks, where they literally "blend into the woodwork", while the two smaller leaf-tailed geckos (U. phantasticus and U. ebenaui) spend more time in ficus bushes, where they are very difficult to distinguish from the twigs and leaves. The bark-mimicking species have developed a flap of skin known as a dermal flap and running the length of their bodies, which they lay against the tree as they rest during the day, and where it scatters shadows and makes their outline practically invisible. In the breeding season, female Uroplatus lay between two and four eggs each. Habitat destruction and illegal wildlife trade are the main threats to the future of these geckos

Madagascar also has several native species of day geckos, forming the genus Phelsuma. Standing's Day Gecko (Phelsuma standingi), for example, is native to the spiny forests of the south and is one of the most coveted by collectors. They have specialized toe pads that enable them to climb smooth vertical surfaces. In the past few years, day geckos have become familiar to American TV viewers as the advertising icon for the insurance company GEICO, whose advertisements feature an animated anthropomorphic Phelsuma gecko that speaks with a British accent.

Over 200 species of frogs have been named and described. All but two are endemic. The majority are native to rainforest environments. In one such area, a montane rainforest in the Andasibe region, 90 species are native, the highest diversity of frogs in the world. A candidate for the world's smallest frog - and perhaps the world's smallest vertebrate - is a minute frog, Stumpffia pygmaea, which measures less than 3 millimeters in length (about one tenth of an inch). Perhaps the most spectacular Malagasy frog is the bright red Tomato Frog (Dyscophus antongili), which secretes poisonous white mucous when threatened. Fat and squat, this toad-like frog is large enough to cover the palm of a hand. The Boophis genus has several brightly colorful species, as does the Mantella genus, including the aptly-named Golden Mantella.


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