Posted by: galapagosinc | June 2, 2010

The life of an Iguana

The iguanas on the Galápagos Islands enjoy a pleasant life with few predators and ample marine algae to feast on.

But every few years El Niño, a tropical Pacific weather pattern, disrupts this, warming the ocean waters and causing the algae to die. Iguanas sometimes go without food for up to several months.

While some iguanas starve, others seem to make it until new algae grow. This survivability may be connected to the iguana’s ability to control stress levels, according to a study in the May 26 issue of the Proceedings of the Royal Society B.

In a stress-inducing situation like that caused by El Niño, iguanas release a hormone called corticosterone. In the short term, this helps the iguanas tap into their own protein reserves. And, for example, when an iguana faces an attack by a predatory hawk, the hormone provokes a response to move faster.

But in the long term, iguanas that cannot turn off the stress hormone expend too much energy too quickly, which is fatal, the researchers found in their survey of 98 iguanas.

“Their ability to turn off their response was what seemed to predict who lived and who died,” said L. Michael Romero, a professor of biology at Tufts University and the paper’s lead author.

A similar stress hormone, called cortisol, exists in humans. During a stressful situation, this hormone triggers what is commonly referred to as the “fight-or-flight” response. Just as in iguanas, the inability to turn off the release after danger has passed can result in serious complications, including post-traumatic stress disorder and brain damage.

NY Times

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