August 6, 2009

Sea Snakes Tail Resembles Head

Venomous sea snakes have evolved to deceive their predators into thinking that they have two heads, researchers reported on Wednesday.

Writing in the journal Marine Ecology, Dr Arne Redsted Rasmussen and Dr Johan Elmberg found that Yellow-lipped Sea Kraits have skin markings that make their tail look like a second head. Also, they noted that the snake behaves as if the tail is another head.

The performance is all part of the sea snake's effort to trick its predators so that it is less susceptible to attacks while searching for food.

Although the snakes are among the most venomous of all snake species, they are vulnerable to attacks from larger fish, sharks and birds.

During their search for food, sea snakes will use their head to probe coral formations. It is during these moments when they become most vulnerable to attacks.

But Rasmussen and Elmberg noted that the Yellow-lipped Sea Krait actually twists its tail in a fashion that is similar to its head movement.

"This may increase the chances of (the snakes) surviving predator attack by exposing a less 'vital' body part," Rasmussen said.

"But more importantly it may deter attack in the first place if [predators] perceive the tail as the venomous snake's head."

The researchers studied 98 Sea Kraits from three major museum collections in Paris, Berlin and Copenhagen as well as the behavior of wild Sea Kraits in Solomon Islands during the Danish Galathea 3 Expedition.

They found that all of the snakes studied had a distinctive color pattern, with a bright yellow horseshoe marking on the tip of the head and the tail. The yellow was deeper than the colors on the rest of the body and the black colorations were much longer than the dark bands on the rest of the body, highlighting the similarity between the head and the tail, they said.

"It is intriguing that this discovery is observed in this species, as one of the key differences between the Yellow-lipped Sea Krait and other sea snakes is that they spend almost equal time on land and in the sea," said Rasmussen.

"They therefore live in two worlds where two very different rules of survival apply. It remains to be confirmed whether Sea kraits use their sea defense tactic of motioning their tails when on land."


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