Four new species of dwarf chameleons have been discovered in Madagascar and one, Brookesia micra, appears to be the smallest chameleon in the world while possibly representing an extreme example of “island dwarfism.”
A team of scientists in Madagascar, led by researcher Frank Glaw, has discovered what now appears to be the smallest amniote in the world. Brookesia micra, a chameleon, is so small that it can fit onto the head of a match. The researchers also discovered three additional species of dwarf chameleons including Brookesia confidens, Brookesia desperata, and Brookesia tristis, all of which are distinct species.
The chameleons were discovered in the northern regions of Madagascar, with the smallest, Brookesia micra, being found on the tiny islet of Nosy Hara. Using flashlights and headlamps the team searched for the reptiles at night, when the tiny chameleons are asleep. According to Glaw, a herpetologist and curator at the Museum of Natural History in Munich, the chameleons are fairly easy to catch. “They are sleeping and you can just pick them up. It’s like picking a strawberry, so it’s easy. They do not move at all at night.”
How tiny is Brookesia micra? In general, the species has a total body length of 29 mm (1.1417 inches), including tail, which is smaller than the previous record holder for smallest reptile, a dwarf gecko Sphaerodactylus ariasae, which has a total body length of 30 mm (1.1811 inches). Adult male B. micra chameleons reach a maximum snout-vent length (SVL) of 16 mm (just over half an inch), while adult females are larger, about three-quarters of an inch in SVL.
One possible explanation for this extreme dwarfism may be what is termed insular, or island, dwarfism, which can occur for a variety of reasons. Island dwarfism is a selective process whereby only smaller animals trapped on an island survive as food and other resources decline. Smaller animals require less resources and smaller territories to survive and reproduce, and are more proficient at processing nutrients. They also have the additional advantage of being able to avoid predators more easily.
The scientists believe that the extreme dwarfism of Brookesia micra may represent a case of “double” island effect. Basically, the larger island of Madagascar was favorable to the evolution of the Brookesia minima group whereas the isolated, tiny islet of Nosy Hara might have favored the extreme miniaturization found in B. micra. The scientists point out, however, that the sea between Madagascar and Nosy Hara is shallow, and that they may have been joined at one time; thus, it remains to be seen if B. micra is actually indigenous to Nosy Hara.
Whereas larger animals are mostly known, miniaturized species often go unnoticed and undetected, and discoveries of dwarf species are generally quite extraordinary. It has been postulated that dwarfism may be an important pre-adaptation for “entirely new patterns of organismal organization. Extremely small animals often display unique behavioral repertoires, and evolutionary novelty may also arise through ecological specialization directly related to size,” say the scientists. Thus, the extreme miniaturization of these dwarf reptiles offers a unique opportunity for study.
Of utmost importance, however, the scientists emphasize, is that the focus be on conservation efforts, as they warn that two of the newly-discovered species are “threatened” because of deforestation and loss of habitat.
Whether the miniaturization of Brookesia micra can be interpreted as a case of “double” island dwarfism is uncertain. Glaw and his team will be returning to Madagascar to continue researching the ever-growing list of dwarf species. And as to whether B. micra is the smallest possible miniaturization remains to be seen. As Glaw points out, “…each time scientists have proclaimed the discovery of the tiniest one yet, another, tinier species appears.” As the saying goes, “It’s a small world (after all)!”
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