Sea snakes are currently not found in the Atlantic Ocean. A new study by the Florida Museum of Natural History explains why this is so.
With a flattened tail, sea snakes are good swimmers and spend all of their lives in the water. Since they don't have gills, they have to come up to the surface for air to breathe. They are found in many parts of the world, from the Indian Ocean to the Pacific Ocean; curiously, though, there are no sea snakes in the Atlantic Ocean.
"Why there are no sea snakes in the Atlantic is a question we've been asking for a long time," said Coleman Sheehy, Florida Museum of Natural History herpetology collection manager. "We know why they are where they are. But why they're not where they're not has been a mystery."
A paper recently published in the Bioscience journal suggests that the reason for the sea snake's notable absence is due to geography, climate and timing.
Although sea snakes evolved about six to eight million years ago, in the Coral Triangle of Southeast Asia, the majority of the species only appeared one to three million years ago. So, by the time any of them could have spread across the Pacific, the Isthmus of Panama had closed, thereby blocking off their access to the Atlantic. Add to that, they require fresh water, so the cold and dry conditions at the tip of South Africa would have prevented any sea snakes from using that route to enter the Atlantic.
Lead author Harvey Lillywhite suggested that the sea snakes' range may expand due to warmer ocean waters, but this is unlikely as climate change will lead to declines in the sea snake population-something which may already been occurred.
"I think one of the reasons we're seeing declines in certain populations is because of changing rainfall patterns," Lillywhite said. "If rainfall patterns aren't conducive to providing water to drink, sea snakes can't survive, even if ocean temperatures are favourable. The availability of freshwater is going to be a huge factor in understanding local extinctions."
Nevertheless, there have been reports of individual yellow-bellied sea snakes on the Caribbean coast of Colombia, but these are likely to be drifters who had somehow made it through the Panama Canal. Coleman Sheehy, Florida Museum of Natural History herpetology collection manager, said that the odds are stacked against them establishing a successful breeding population.
And this would be good news for the creatures in the Atlantic Ocean. In the event that sea snakes did manage to make it to there, "nothing in the Atlantic would be prepared. Prey wouldn't know how to protect themselves, and predators would have to quickly learn that sea snakes are venomous and likely have toxins in their skin," said Sheehy.