Snakes on a Reef

Dive on a coral reef in places like Fiji, the Philippines or Indonesia and you may encounter one of the most venomous creatures on earth. The banded sea krait can administer a dose of neurotoxin that is ten times more potent than a rattlesnake bite. This fact can make for a sensational headline, but the reality is that that these sea snakes pose no real risk to humans, and can be fascinating to watch.

 

The banded sea krait, aka "banded sea snake” or yellow-lipped sea krait does not attack divers. This species is actually quite docile, and is more likely to hide or flee if it feels threatened. Yes, there are rare cases of humans getting bit, but this almost always involves a fisherman attempting to remove a snake from a trap or net. And in those cases, only 3 percent of bites prove fatal. Since sea snake sightings aren't a cause for alarm, divers who keep a respectful distance have nothing to fear, and have a rare chance to observe these fascinating creatures as they patrol the reefs in search of a meal. 

Sea Snakes have a long thin body, and can reach lengths of five feet. Any snake over three feet is a female as they grow larger than the males.

Sea snakes don't actually live underwater. They are air-breathing reptiles that happen to be pretty good at holding their breath. These snakes can remain underwater for 15 to 30 minutes and dive to depths of more than 250 feet, but like sea turtles, they must eventually surface for air. While they are underwater they are probably looking for a meal.

 

Sea kraits are very active stalkers, constantly slithering in and out of the crevices of the reef in search of their favorite prey, which is eels. Once an eel is cornered, a quick shot of venom renders it immobile, and the krait will swallow it's victim whole. Like all snakes, sea kraits can expand their jaws to engulf a meal larger than itself. After filling it's belly, a sea snake will return to land to rest and digest.  These snakes also return to land to lay eggs, and even to drink. They don't take in moisture from the sea, and must occasionally get a sip of fresh or brackish water.

 

If you follow a sea snake that's on the hunt, you may have company. As the snake slithers through the crevices of the reef, it may disturb small fish and invertebrate and flush them from hiding places. This activity can attract an entourage of predators that follow in the snake's wake, hoping to cash in on the disturbance.

 

One distinctive feature you may notice when watching a sea snake is the way it moves through the water. As an adaptation to the ocean, these snakes have flattened tails with exaggerated vertical profiles. This paddle-like tail helps the snake move through the water with a sculling motion, and also provides an additional benefit. When hunting, a sea snake often has its head buried in a crevice, leaving it's unprotected tail waving in the water. The vertical tail section mimics the head, giving would-be predators second thoughts about nipping at what appears to be a poisonous mouth.

 

The alternating black and white skin pattern of a banded sea snake is distinctive and easy to recognize, but you might want to take a closer look to be sure you haven't found one of the reef's clever impostors. The banded snake eel mimics the sea snakes coloration, and uses this false advertising to hunt out in the open during daylight hours. These eels are not venomous, but predators don't know that, and tend to steer clear based on the stripped color pattern. To tell snake from eel, notice the shape. Sea snakes have a more rounded body and a tail that is paddle like in shape.  The banded eel has a taller and thinner profile, with large downward-facing nostrils and an elongated dorsal fin running the length of its back.

The Banded Snake Eel uses mimicry for protection. It's coloration matches that of the banded sea snake, but a closer look reveals some anatomical differences.

Whichever species you happen across during a dive, it's worth spending a few minutes hanging back and watching these colorful hunters in action.