Crew Blog | Craig Thomas: Encountering Sea Snakes

Written by Craig Thomas

Aloha all. This is the first medical blog posting for the Indian Ocean legs of the Worldwide Voyage. The blog will cover medical aspects of the wildlife we encounter plus the injuries and illnesses we’re encountering on our passage. Please, send questions and topics youʻd like discussed in upcoming blogs.

Our passage since leaving Darwin, Australia has been excellent, calm seas, spectacular animal life and several days becalmed inside isolated Ashmore Reef. The reef teams with colorful corals, giant clams, huge sting rays and the occasional black tip reef shark. Above water were multiple species of terns, noddies and squadrons of brown boobies.

A giant clam nestled among the reefs of Ashmore.

The calm waters offshore enabled us to see dolphins, false killer whales, large orange jellyfish and numerous sea snakes swimming along as we passed. The snakes undulated on the surface like wiggling ropes. I’m used to seeing them underwater but not from on deck. These snakes are air breathing venomous creatures distantly related to cobras and commonly mistaken for eels. They primarily eat fish, paralyzing them with their venom, then swallowing them whole. Sea snakes can dive as deep as 300 feet and hold their breath for two hours. There are at least 52 species of sea snake–all venomous in the tropical Pacific and Indian Oceans. Only the pelagic yellow-bellied sea snake visits Hawaiʻi.

Sea snake venom is among the most potent poisons known, and can cause paralysis and death. The snakes are not aggressive. Swimming with them is safe, and most bites occur when fisherman catch them. Our plan on Hōkūleʻa is to cut the line if we accidentally hook one.

One of many sea snakes spotted en route to Ashmore Reef in the Indian Ocean.

The snakes’ mouths are adapted to biting small fish, but they can bite humans if provoked. Surprisingly, the bites generally don’t hurt, and look like a pin prick. Fortunately, most of the time that sea-snakes bite humans they don’t inject venom. Sadly, sometimes they do and these bites can be fatal. Most rapid recorded death after a bite is two and one-half hours; without antivenin mortality is about 8%; with antivenin this drops to about 1%. Since the venoms are closely related the same antivenin works for many types of sea snake.

The only first aid is applying a pressure bandage to the bite–do not cut or suck on the bite. The toxin is not affected by heat/cold or changes in pH. If the person has no symptoms after eight hours the snake did not inject venom. Advanced medical care includes ventilatory support for respiratory paralysis, antivenin and treatment of muscle break down and kidney failure.

Watching the snakes swim along Hōkūleʻa’s side enriched our voyage, reminding us of the multiple niches the tropical seas provide for diverse life forms.

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