Sea snakes spend their entire lives living under water, but they don't drink sea water. These animals will go up to seven months without drinking. The snakes will allow themselves to dehydrate for months at a time, while living underwater. During this time, the animals can lose up to one-quarter of their body weight. Only when the rains come are they are able to collect the life-sustaining drink.
Harvey Lillywhite of the University of Florida led the study, questioning the idea that all marine vertebrates drink sea water. Salt from the water is removed through the use of salt glands. This idea is commonly printed in many biology textbooks. Although it is accurate these structures do remove salt from water, no sea snake tested by the team drank seawater.
When precipitation occurs, the snakes scurry to the fresh water. Because fresh water is less dense than salt water, a thin layer of nearly salt-free water exists on top of the surface for a short time before mixture occurs. Sea snakes seem to have the ability to know when storms are about to arrive.
"We think they almost certainly know that it rains because their behavior changes during the approach of a tropical storm as the atmospheric pressure changes," Lillywhite said.
Laboratory studies of captive sea snakes were combined with field studies of the tropical Yellow-bellied Sea Snake. This animal can consume up to 25 percent of its body weight in water in one visit to the surface.
An ability to go months without drinking fresh water may help sea snakes survive dry spells. In some areas of the world, these seasonal changes can turn seas into a virtual desert for more than six months at a time.
Lillywhite and his team spent more than three years studying sea snakes, trying to determine what, and how, these marine animals drink. Animals both in the laboratory and in the wild refused to drink salt water.
Global climate change and rising temperatures could lead to longer, more severe dry spells, including in the water. This could add stress to sea snakes, possibly reducing populations.
As a follow-up study to the snake study, investigators may carry out an analysis of the drinking habits of sea turtles. This could help determine if those animals are also dependent in whole, or in part, on fresh water.
The study of drinking habits of sea snakes was published in the Proceedings of the Royal Society B.
