Washington, July 1 : A new research has discovered that a chameleon from arid southwestern Madagascar spends up to three-quarters of its life in an egg, and its lifespan after hatching is a mere 4 to 5 months.
Among the 28,300 species of known tetrapods, or four-legged animals with backbones, no other known four-legged animal has such a rapid growth rate and such a short life span as this chameleon.
"It really is a huge surprise," said Christopher Raxworthy, Associate Curator in the Department of Herpetology at the American Museum of Natural History. "Adding to that, until now, the short life span of chameleons in captivity has always been considered as a failure to thrive. We need to rethink this," he added.
Most mammals, reptiles, birds, and amphibians (all tetrapods) typically live 2 to 10 years, an average bracketed at the upper end by some long-lived animals and at the lower end by a handful of animals that only live for about a year.
The males in nine species of marsupials die off after a year, for example, as do most adults in about twelve species of lizards.
But the chameleon described here, Furcifer labordi, not only has a brief, yearly life cycle, but the bulk of that time is spent incubating inside an egg.
Once outside of the egg, all individuals in the population die within 4 to 5 months.
Kristopher Karsten, a graduate student from the Department of Zoology at Oklahoma State University, discovered the unusual life cycle almost by accident.
"I showed up late in the season and found something weird. There were no juveniles," recalled Karsten. "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," he added.
Now, after five seasons of data and sightings of nearly 400 individuals, 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 2.6 mm (0.1 inches) a day-up to two orders of magnitude greater than other known lizard growth rate.
In less than 60 days, for example, there can be a 300%-400% increase in body size for males to reach adulthood.
After reaching maturity, the population reproduces, and females burrow through about 138 mm (5.4 inches) 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.