World's tiniest chameleon: How did it get so small?

Scientists recently discovered four new species of chameleons in Madagascar. One of them – Brookesia micra – is the smallest chameleon in the world. This species may have evolved through a phenomenon known as island dwarfism.

A juvenile Brookesia micra chameleon sits on the head of a match. Researchers in Madagascar have discovered what might be the world's smallest reptile.

If you think finding a chameleon is hard, try finding one that can fit on the head of a match.

A group of scientists have done just that. They found four new species of chameleon in Northern Madagascar including the world's smallest, Brookesia micra. Adults reach a size of just over an inch long, making it one of the world's smallest vertebrates.

Needless to say, it was difficult to locate the chameleons during the day while they were active. But, with the help of flashlights, the scientists spotted them sleeping at night on plants a few inches off the ground.

Brookesia micra may be the world's smallest lizard, but it's not the smallest vertebrate. Holding this title is a frog from Papua New Guinea that measures about a third of an inch. The miniscule frog, Paedophryne amanuensis, broke the record held by a slightly larger-sized swamp-dwelling fish from Indonesia.

There is some controversy surrounding this title, as there exists an anglerfish native to the Philippines that can be as small as a quarter of an inch. But this fish is a parasite, spending its adult life attached to the female of its species.  

How did this chameleon get so small? One explanation is a theory known as island dwarfism. This size adaptation can occur for a variety of reasons on islands such as Madagascar. Smaller animals need to consume fewer resources to survive and reproduce, which is advantageous when food is scarce. Often dwarfed creatures are specialized and more efficient at processing nutrients. Small animals can also better utilize little shelters, to help them avoid predators and harsh environmental conditions.

Other island animals tend toward gigantism. Being big can mean fewer predators or less competition for resources. Mammals, for example, grew in size following the extinction of the dinosaurs.

Rates of change in mammals' sizes were described in a January article in the Proceedings of the National Academy of Sciences.

Each species' physiology limits the extent to which it can grow or shrink. This chameleon may be the smallest possible vertebrate with complex eyes. But maybe not. The search for the smallest will undoubtedly continue, as the limit of miniaturization is as yet undefined.

Christopher J. Raxworthy, a herpetologist at the American Museum of Natural History, told The New York Times of a recent trip to Madagascar in search of chameleons, "And that’s one of the best things about being a scientist — there is always the thrill of your next discovery."

The chameleon study was published on February 14 in the online journal PLoS ONE.

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