June 30, 2008 -- "Live fast and die young" takes on new meaning in light of a recently discovered chameleon that spends over half its life in an egg before living hard for a handful of months and then dropping dead of "old" age.
With an existence akin to that of an annual plant, the chameleon, Furcifer labordi, breaks the world record as the four-legged animal with the shortest known lifespan.
Kristopher Karsten, an Oklahoma State University zoologist, made the discovery with his colleagues after several months of work at Madagascar's Ranobe Forest in the southwestern part of the country. The scientists first observed that, during the region's dry season, developing eggs that incubated for eight or nine months represented the chameleon's entire population.
He and his colleagues published a paper on the lizard in the current issue of the Proceedings of the National Academy of Sciences.
Otther chameleons spend large portions of their time in their eggs, but this particular species "has an astonishingly nearly 3 to 1 ratio of incubation to post-hatch life," Karsten told Discovery News.
For the first two months in the egg, the chameleon exists in a state of "physiological arrest" and does not utilize much, if any, of its egg yolk nutrients.
"The chameleons commence developing and growing (inside the egg) only when the wet season approaches," Karsten said.
Since many forest plants and animals slow down during the dry season, he believes the unguarded eggs have "a bit of a built-in safety net." Snakes, however, may eat them on occasion.
The colorful reptiles then hatch en masse and start to eat -- a lot.
"They are eating machines," Karsten said. "These chameleons eat any arthropod that crosses in front of them. If you sit and watch them for as little as five minutes, you will see them catch food several times."
They need ample energy in order to grow fast and reach sexual maturity in two months, he explained. During this voracious appetite phase, very little social interaction takes place, but that dramatically changes when the reptiles reach adulthood.
At that time, "males engage in very fierce, physically intensive combat and courtship begins," Karsten said. "Courtship is a bit odd in this species in that it's not as romantic of an idea as many people might think -- males and unwilling females will often engage in physical fights, and we even see this between pairs that eventually end up mating."
Color plays a big role in mating, with females acting like living mood rings.
The scientists theorize the chameleons are pumped up with testosterone, which is linked to aggressive behaviors and can promote mating, fighting and territorial disputes. On the flip side, it can also suppress the immune system.
After just two or so months of frenzied mating and egg-laying, the chameleons start to move more slowly, lose body mass and have trouble gripping branches. Many of them literally drop dead by falling from trees after just four to five months of life outside of their eggs.
The World Conservation Union includes the chameleon in its IUCN Red List of Threatened Species. It has been classified as "vulnerable," but that may soon change.
Another study conducted by researchers at the American Museum of Natural History found that many of Madagascar's chameleons, along with certain geckos, skinks and frogs, are shifting their habitats in response to global warming. In the country's mountainous northern regions, several of these animals appear to be scrambling ever upward in a desperate attempt to beat the heat.
Lead author Christopher Raxworthy said that "with a phenomenon like global warming, species will move upslope, and so eventually may still lose all of their habitat and go extinct."
Karsten pointed out that additional studies on the short-lived chameleon may directly benefit humans, since the recent findings "provide an ideal system to try and address how vertebrates age."
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