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Dive Dry with Dr. Bill

#555: Banded Sea Krait

One of the things I absolutely love about writing columns on the critters I find in exotic places is that I always learn something new. I place a strong emphasis on experiences that broaden my understanding of the natural world, although one species (Homo sapiens) is pretty well beyond my ability to comprehend. For today's topic I am returning to the Philippines and a critter unlike any we find in the eastern Pacific or the Atlantic. They are only found in the Indian Ocean and western Pacific.

In preparation to write this, I opened all five of my field guides for the Philippines and could not find a single entry about this very interesting critter. Field guides to the marine environment usually focus on one of four things: algae (seaweeds), invertebrates (lobsters, clams and the like), fish or marine mammals (like seals). Rarely do they include the group this critter belongs to, although some guides do talk about one of its relatives, the sea turtles. Today I'm focusing on a marine reptile, the banded sea krait (Laticauda colubrina).

What the heck is a sea krait you are undoubtedly asking. Well, don't feel too bad... I had to do research to determine the difference between it and what are known as true sea snakes. Some of you are aware that there are snakes that may be found in some tropical waters. But how many of you know why a krait is a krait and not a true sea snake? I didn't.

Apparently this group represents a more primitive line of sea snakes that have not completely made the transition from land to salt water (I'm almost there). Sea kraits still return to land and are able to move on beaches due to the enlarged scales on their ventral surface (aka, belly). As far as I know, it's not really that they are homesick for dry land. They do so to lay their eggs on beaches instead of giving birth to live young which hatch within the body like the true sea snakes. Oh, and their nostrils are also located in a different position than those of true sea snakes... but just how close are you going to look?

The species I observed and filmed in the Philippines, the banded sea krait, is also known as the yellow lipped sea krait. It is found from Bangladesh to Thailand and out to Indonesia, the Philippines and the western Pacific Ocean. Because sea snakes do not have gills, they must come to the surface to breathe. Therefore they are generally found in shallow water habitats around reefs. Apparently sea snakes have extremely large left lungs which may extend throughout most of the body. This allows them to stay underwater for a few hours. As a former high school swimming champ, I have enlarged lungs but nowhere near THAT big! The snake's extended lung may also assist in maintaining proper buoyancy. I do use mine for that since we were taught to do so in the dark ages before BCDs were common.

These snakes are fairly easy to recognize with alternating bands of black and either silver or blue running from head to tail. They reach lengths up to 6 1/2 feet although most of the ones I saw were about half that size. The tail is paddle-shaped and allows them to swim efficiently underwater. I prefer to use fins since my tail seems to have disappeared millions of years ago. The flattened surface also acts like a rudder.

Males are smaller than females and reach sexual maturity earlier (18 months vs 18-24). This species may travel long distances to reach their breeding areas, and dense populations may gather at this time. Courtship and mating occur on land and the eggs are laid on or just under the sand. Banded sea kraits will also leave the ocean several times a month, generally at night, to digest food and slough off old skin.

These snakes possess a powerful venom that affects the nervous system and paralyzes the muscles of prey or potential predators and other threats. They are close cousins to the land-based cobras and their toxin is similar but much stronger. They feed primarily on crabs, cuttlefish, squid, eels, fish and fish eggs. Like in land snakes, the forked tongues are used to sense prey chemically through smell. Fortunately for humans, they are not aggressive and their mouths are fairly small and generally they are not able to bite and inject venom into humans.

Humans in the regions where they are found may hunt them both for their meat and their skin. Many years ago I ate a local rattlesnake, prepared by a real Native American "squaw" (her term). It tasted like chicken. Although I'm not really sure what was in all the dishes I ate while in the Philippines, if it included sea snake it probably was like "chicken of the sea" (or maybe rooster fish). Whatever was in my meals there, they tasted great!

© 2013 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Images of banded sea krait (Laticauda colubrina) from the Philippines.

This document maintained by Dr. Bill Bushing.
Material and images © 2013 Star Thrower Educational Multimedia