How The Gila Monster Survives Dry Months

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The venomous Gila monster (Heloderma suspectum) lives in the desert southwest, where water can be scarce for months at a time. How does the reptile survive the drought? Not through its meals but by binge drinking, says scientists from Arizona State University in a study that appears in the Journal of Experimental Biology.

Scientists had thought that Gila monsters might be able to maintain their internal water balance with only the water gained through its meals of vertebrate nestlings and eggs. Other animals, including carnivorous reptiles like the heath monitor of Australia, are able to survive in dry places with only dietary water. And the Gila monsters’ prey is about 70 percent water, so it might be a decent source of hydration in dry times.

The researchers took a dozen Gila monsters and let them get comfortable for a time, drinking as much water as they like, before draining their bladders. Then they fed half the reptiles and, keeping them in a dry, hot environment, waited to see how long it would take before the monsters became dehydrated.

It took 32.5 days for a Gila monster to become dehydrated whether or not it had eaten. Feeding the reptiles extra food gave a monster a little more time, but since prey is scarce in the wild and Gila monsters eat infrequently, particularly during dry spells, the researchers conclude that extra meals can’t be the solution.

The only way for a Gila monster to survive months of dryness, the researchers say, is to drink up whenever they encounter water and store that moisture in their bladders. After their hidden supply runs dry, the reptiles can survive for a while, but they’ll soon have to hope for the rains to return.

Image courtesy of flickr user Joachim S. Müller

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