An Ectothermic Mammal Found?

A prehistoric goat survived for millennia on a resource-poor island by living like a reptile—changing its growth rate and metabolism to match the available food supply, according to a new study of the animal's bones.

The discovery marks the first time scientists have seen this cold-blooded survival strategy in mammals.

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Fossils of the ancient goat, called Myotragus, were first found on Majorca in the early 1900s. The bones show the species lived on the island for more than five million years.

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But the new study, which looked at the bone histories of several Myotragus individuals, revealed that the goats may have fine-tuned their growth and metabolic rates both seasonally and during irregular times such as droughts—just like reptiles.

"This way, it burned only the energy that was available from the environment, slowing down the 'fire of life' in times when resources became scarce," Köhler said.

The lizard-like lifestyle, however, meant that Myotragus's newborns were extremely small—the sizes of large rats—and the young took years to reach adult size.

The goat also saved a lot of energy in its nervous system—among the body's most "costly" tissues—by sporting a brain only half the size of a similar-size hoofed mammal and eyes only a third as large.

The combined effect was that Myotragus was sluggish, with slow reaction times, the bone study suggests.

Like modern-day reptiles, the goats probably "saved as much energy as possible just lying around and basking in the sun," Köhler said.

"The postcranial skeleton indicates that this animal was not able to run, jump, or move fast around, and [would have been] easy prey."

Someone have a link to the paper? I'd like to see if this is really the case that the goat lost endothermy. It has been posited for crocs, but not many other animals.

Note the brain size decrease, folks.