You think kids today are immature? A species of chameleon in Madagascar spends most of its lifespan incubating inside its shell. After four or five months out in the world, it dies. Total pre-hatching and post-hatching existence: about 1 year.
In fewer than 60 days, body size for males can quadruple or quintuple as they reach adulthood. No other known four-legged animal has such a rapid growth rate and such a short life span, says researcher Kristopher B. Karsten of Oklahoma State University. The finding, detailed in the July 1 issue of the journal Proceedings of the National Academy of Sciences, raises issues about conservation of short-lived creatures, especially on biodiversity-rich Madagascar where forest habitats are being destroyed rapidly due to pressures relating to poverty and political instability.
"We've identified a species that does something really different from the others, but what is driving this system?" Karsten said. "One bad year could wipe out these chameleons."Most mammals, reptiles, birds and amphibians typically live two to 10 years. Some, including turtles and humans can live for a century. Only a handful of animals live just a year. The males in nine species of marsupials die off after a year, for example, as do most adults in about 12 species of lizards. Karsten discovered the unusual life cycle of the chameleon, Furcifer labordi or Labord's chameleon, almost by accident. "I showed up late in the season and found something weird," Karsten said. "There were no juveniles. But by February, I found carcasses all over with no signs of mutilation or predation. The population plummeted -- we've never seen this with other lizards."Now, after five seasons of data and sightings of nearly 400 of the lizards, the life cycle of F. labordi can be described. Hatching begins with the rains in November, and, once emerged, the chameleons develop rapidly, growing up to 0.1 inches (2.6 mm or the width of the base of a fork tine) a day -- much faster than any known lizard. After reaching maturity, the population reproduces, and females burrow through about a half foot of sand to lay their eggs. Once covered, the eggs wait out the dry season for the next 8 to 9 months, and all adults die.
"It is amazing to think that for most of the year, this chameleon species is represented only by developing eggs buried in the ground," said Christopher J. Raxworthy, of the American Museum of Natural History in New York, who helped with the chameleon research along with Laza Andriamandimbiarisoa of the Universite d'Antananarivo in Madagascar and Stanley Fox at Oklahoma State. The short life span of F. labordi, which only lives in southwestern Madagascar, comes as a "huge surprise," Raxworthy said, adding, "until now, the short life span of chameleons in captivity has always been considered as a failure to thrive. We need to rethink this."The chameleon's short life could be an adaptation to Madagascar's highly variable climate, Karsten and his colleagues write. Also, dying young can drive the evolution of growing fast and reproducing early in life, they say. The project was funded by the National Science Foundation.
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