Even though they live in water, sea snakes can live without water for long periods of time and often dehydrate themselves for months on end.
The researchers looked at Yellow-bellied sea snakes and found they refuse to drink salt water, and instead wait for fresh rainfall to drink, a University of Florida news release reported.
"These snakes refuse to drink salt water, even when dehydrated," Professor Harvey Lillywhite, who worked on the study, said in the news release. "They need fresh water to survive."
Researchers looked at the snakes both in their natural habitat and in a laboratory setting, and found they did not drink salt water under any circumstances.
This disputes the popular theory that marine invertebrates evolved to quench their thirst with saltwater. Many physiology textbooks claim marine reptiles filter out some of the salt in the drinking water through a special gland.
"No sea snake we have tested drinks sea water," Lillywhite said.
"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," he said.
Fresh rainfall is less dense than seawater, causing it to form a "film" at the surface. Yellow-bellied sea snakes are usually found deep in the ocean but surface during rainfall or right after to take a drink. They will consume anything from one sip to 25 percent of their body mass.
The researchers studied the snakes in Costa Rica, where it can go up to seven months without raining. Experiencing this much dehydration would be "way past lethal for a human," Lillywhite said.
A reduction in rainfall due to climate change could be threatening the sea snakes. In Northern Australia the populations have been declining over the past decade, and two species are believed to be extinct.
"Understanding the water requirements and drinking behaviors of marine vertebrates could help with conservation efforts," Lillywhite said. "In areas of intensifying drought, they will need to move or die out."
