Beaked sea snakes have learned to live in shallow ocean waters. But their real claim to fame is that their venom is some of the most potent on earth.
The beaked sea snake is a deadly sea snake, that was recently reclassed as two separate but similar species. They’re highly aggressive, and kill many people—mostly fishermen—each year. They’re usually an olive-grey color that’s ideal for blending in with the sea floor within their range, from East Africa to Australia.
They are one of the deadliest snakes on Earth, so why haven’t more people heard about them? It’s because they’re a sea snake, which severely limits how many people come into contact with them.
Beaked Sea Snake Facts
There are two species of beaked sea snake. There were initially thought only to be one, which ranged from East Africa all the way to Australia.
But recent DNA testing found that specimens caught near Australia were actually a different species to the kind in the Indian Ocean. The ‘original’ and more common kind is Enhydrina schistosa, while the Australian species is now called Enhydrina zweifeli. As you can tell from their scientific names, they’re still classed within the same genus, but as two different species.
It might surprise you to learn that this is quite a common occurrence. Biologists argue all the time over whether a particular species belong in this genus or that genus, or whether this family should even be classed as a family or not. Colubrids are an excellent example.
Colubridae is the biggest snake family, not because all the snakes are alike—but because it’s a ‘garbage bin taxon,’ a family that snakes are classed in when there’s nowhere better to put them.
However, the two beaked sea snake species look very alike, and were thought to have been the same species for decades. So, why are scientists saying they’re different?
Beaked Sea Snakes and Convergent Evolution
The two snakes are an example of convergent evolution. That’s where two animals evolve, entirely separately from one another, to fit the same ecological ‘gap in the market’ in two different locations.
Sharks and dolphins are an example; they look quite similar, with fins on their back, big tails, and long snouts. But they’re two completely different kinds of animal.
A scientist from the University of Adelaide, Kanishka Ukuwela, published a paper in the journal Molecular Phylogenetics and Evolution. When they ran DNA testing on specimens from Australia and Africa, Ukuwela (and the co-author of the paper, Bryan Fry) found that they have completely different DNA sequences.
They evolved from different ancestral species. But similar habitats, prey, and predators mean that they evolved to be the same color, have a similar size and shape, and have similar venom!
How to Identify a Beaked Sea Snake
Let’s take a look at what makes the beaked sea snake so distinctive:
- Beaked sea snakes have a distinct nose. Their lower jaw is flat and straight, while their nose is curved downwards at a 45-degree angle to meet it in a rounded point. This beak is like the opposite of a western hognose snake’s snout, which is curved upwards. Their head and jaw are quite small for their size.
- They are a uniform olive-gray color, with a lighter, almost white underbelly. They have stripes all along their body, reasonably well defined, but slightly variable in width. These stripes are a darker gray color. All along their body, they have a mottled appearance because of black borders around each scale. Their body is thick and wider than it is tall.
- Beaked sea snakes, like other sea snakes, have a paddle-like tail. This is essentially an elongated and laterally flattened paddle—almost like a fish’s tail. It’s nothing but skin, bone, and muscle, the sole purpose of which is to help them move forward more quickly.
- Another adaptation for living underwater is that they have special nostrils that work like valves, letting out air when necessary, but staying closed otherwise.
- They also don’t have the same ventral (belly-side) scales that land snakes do, since they don’t have to move along the ground.
They’re one of the most common sea snakes, so if you spot a swimming snake, there’s a good chance that this is the species you’re looking at.
Length, Weight, and Size
Beaked sea snakes are on average about 35 inches long. That’s fairly typical for a sea snake. The longest specimens found have been 55 inches long, which is about 4.6 feet.
Sexual dimorphism isn’t apparent in these snakes, meaning that the males are the same size as the females. That’s unusual compared to other snakes.
They’re squat and stocky, too, with a body that’s thick for a snake. According to a study on Indian specimens, the average weight was somewhere around 2.5 to 3kg, or 5.5 to 6.5lbs.
However, this was a relatively small sample size, and very few studies have found it necessary to find out how much these snakes weigh!
Sea snakes don’t have an easy time under the sea. Typically, most young die before they reach adulthood. However, the problem is particularly bad for beaked sea snakes.
Only between 10 and 20% will survive their first year, and only 6% of females will grow old enough to breed. Aside from this, though, little is known about how long-beaked sea snakes live. The problem is that sea snakes generally are hard to track over long periods of time.
The best guess we have is that these snakes only reach four years old on average. That’s due to large-scale predation. They make up for it by being exceptionally fertile, and maturing early. By comparison, other sea snakes like Aipysurus laevis normally survive for about 15 years.
These snakes, like almost all sea snakes, aren’t really ‘sea’ snakes. They don’t go out into the deep ocean. They prefer staying near the coast, specifically in shallow reef waters.
Here, they can easily hunt for prey in all the nooks and crannies that a coral reef offers. Further out to sea, they wouldn’t be able to hunt, because they aren’t as fast as a fish.
These waters are shallow, clear and beautiful—the kind you would see in holiday photos! It might surprise you to learn that beaked sea snakes are also comfortable up to ten miles upstream in tidal rivers, or in estuaries.
They aren’t like saltwater fish, that can’t survive in fresh water. Beaked sea snakes still need to drink fresh water to survive. To do so, they’ll wait until it’s raining, and quickly drink the top layer of water before the fresh raindrops mix into the ocean.
Where Do They Live?
Beaked sea snakes have a broad natural range. You can find them all across the Indian Ocean:
- As far west as the Persian Gulf (near the Middle East)
- All the way along the African coast down to Madagascar
- Off the coast of South Asia, in India, Pakistan, and Bangladesh. This is where they are most common in the wild.
Head south and even further east from there, and you can find them all around southeast Asia, i.e., Thailand, Vietnam, and Malaysia. The furthest extent of their range is Australia and New Guinea—this is where you’ll encounter Enhydrina zweifeli.
They haven’t made their way out across the Pacific, for the simple reason that they aren’t deep sea snakes. And you can’t find them in the Atlantic because it’s too cold for them to head around South Africa, to the west coast of Africa.
Food and Diet
Sea snakes usually live on fish, and beaked sea snakes are no exception. According to a paper published in Copeia, 80% of this snake’s diet consists of tachysurid catfish.
These are fish like the yellowhead catfish, which look a little like elongated goldfish, with the typical catfish whiskers under their jaw. They’re quite small, usually clocking in at around 4 or 5 inches.
Aside from these catfish, beaked sea snakes also eat plotosid catfish and puffer fish (15% of their diet). The rest of their diet is any small fish that they can find. They hunt by swimming, slowly, just above the sea floor.
When they come across a fish, they’ll swim up alongside it. Then, they’ll lash out, opening their mouth as wide as they can and swinging their head to the side. This isn’t exactly an efficient method of hunting.
The snake will then bite and hold on to their prey. At the same time, they’ll swim forward, so that the pressure of the water keeps the prey pressed into their mouth. Once their prey is incapacitated or dead, they’ll juggle it—letting go and biting it again—until swallowing it head first.
Are Beaked Sea Snakes Endangered?
No, beaked sea snakes aren’t endangered—because their range is so broad. They’re listed by the IUCN as a species of ‘Least Concern.’ This means that they aren’t considered anywhere near endangered. They’re so widespread, and they’re so common, that they’re highly unlikely to face any threats significant enough to render them extinct.
That being said, that’s the current opinion of the IUCN. It doesn’t mean they can avoid environmental challenges. Ocean acidification, for example, is a significant threat to their natural habitat (the coral reef).
Acids and various chemicals pumped into rivers by industry eat away at coral reefs, gradually eroding them—and it takes millennia for them to grow back. If this continues, the beaked sea snake will have far fewer places to live.
However, they still shouldn’t have a problem. Beaked sea snakes mature very quickly, and give birth to many offspring at once. This makes them a resilient species, able to robustly withstand events that damage population numbers.
It’s likely that beaked sea snakes mate each year, although scientists can’t say for certain. They’ll mate in warm waters, at the same time each year, between September and October.
These snakes are ovoviviparous. That means they ‘give birth’ to live young, just like mammals do. But there’s one crucial difference. The beaked sea snake, like all ovoviviparous snakes, does form eggs like other snake species. She just doesn’t lay them.
After mating, the eggs will be fertilized, but the snakes will stay inside the mother until they’re old enough to hatch and crawl out. When they’re born, young are about 9 inches long.
Why do sea snakes give birth to live young? Because the snakes inside the egg need oxygen. If they were laid underwater, they wouldn’t get any from the water around them.
So, the mother will provide them with enough oxygen, plus she’ll keep them safe inside her throughout pregnancy. Other sea snakes get around this problem by laying eggs on land.
There are conflicting answers as to how many young beaked sea snakes actually give birth to. Some sources say that they only give birth to a few—like other sea snakes—between 5 and 10.
But other sources (like Heatwole) claim that they have large broods averaging 18 at a time, which is far more than other sea snakes. Only Notechis scutatus has more, at just shy of 24 on average.
The correct answer lies in between, since mortality of young beaked sea snakes is quite high.
Beaked Sea Snake Venom and Bite
Beaked sea snakes are very venomous snakes. They’re responsible for more bites and more deaths than any other sea snake.
Are Beaked Sea Snakes Aggressive?
Beaked sea snakes are remarkably aggressive for a sea snake. Other species, like banded sea kraits, will either try and hide or swim away when they see somebody approaching.
This means that even though they’re highly venomous, they’re not very dangerous to humans. But beaked sea snakes are an exception.
Harold Heatwole said it best in his book, Sea Snakes. He described beaked sea snakes as “cantankerous and savage.” In plain English, that means they’re bad tempered and likely to attack.
Let’s say, for example, that you’re scuba diving off the coast. Most sea snakes would rather avoid you than get close. But when approached, if you seem dangerous, a beaked sea snake will be confident enough to stand their ground.
If you continue to threaten them, they’ll bite, hard and fast. Not only that, but they might bite you repeatedly, potentially tagging you with even more venom.
This is exacerbated by the fact that most encounters between beaked sea snakes and people are due to fishing. When a fisherman catches them in their net, these snakes are even more aggressive—they’ve just been forcibly pulled from their natural environment, and brought face to face with a big, scary potential predator. This is how the majority of sea snake bites happen.
Something that usually surprises people about sea snakes is that their fangs are tiny, relative to how venomous they are. The public’s perception of deadly snakes is usually that the more venomous the snake, the longer and more frightening their fangs are.
Sea snakes, though, have much shorter fangs. The beaked sea snake’s fangs are only about 1/5 of an inch long. They curve backward, as do the rest of their teeth, which line the sides of their mouth in rows like ours. They don’t need very long teeth—remember, their venom is for killing small fish more than anything.
They work like all other snake fangs. They’re hollow, and connected via two narrow ducts to two venom glands. These glands are at the rear of the head, just before the neck.
Snakes can create enormous pressure in these glands by squeezing their muscles, causing the venom to shoot out into the bite wound they’ve just made. It only takes a fraction of a second.
The LD50 of their bite is estimated to be 0.1125mg/kg. If you don’t know, the LD50 is the ‘median lethal dose.’ That’s the exact amount required to kill each of 50% of any number of test subjects.
There are many ways to administer venom, including intravenously, under the skin, or into muscle tissue. But if you inject the venom into the same place, and use the same kind of test subject (e.g., mice), then you can compare two snakes’ venom together.
The beaked sea snake has some of the most potent venom on the planet. King cobra venom, for example, has an LD50 of 1.09mg/kg. Black mamba venom has an LD50 of 0.28mg/kg. So, pound for pound, beaked sea snake venom is deadlier.
The only trouble is that they have far less than a king cobra does. If they had the same amount, they’d easily be one of the deadliest snakes.
What Does Beaked Sea Snake Venom Do?
A paper in Toxicon detailed exactly what happens when a beaked sea snake bites you. A group of scientists analyzed three cases of ‘severe envenoming’ to see what they could learn. They found three patients who sought medical help from hospitals in Sri Lanka, within the snake’s natural range.
The first case was a man who developed ‘severe myalgia’ after he was bitten. Myalgia means pain—specifically in the muscles. He survived, but was in agony for seven days as the effects wore off.
The second patient, a fisherman, developed ‘gross myoglobinuria.’ This is a symptom of rhabdomyolysis, where the muscles actually degrade while you’re still alive, and myoglobin from inside the muscles is excreted through urine.
These effects occurred because beaked sea snake venom is myotoxic. Myotoxic venom attacks muscles, causing severe necrosis (tissue death) throughout the entire body.
The point is that, if enough venom is used, your diaphragm will stop working and you will die from not being able to breathe. The third patient experienced full-on rhabdomyolysis, and died just a few days later from cardiovascular collapse.
Can a Beaked Sea Snake Kill You?
Beaked sea snakes have more than enough venom to kill a person. Their bites release between 8 and 9mg of venom each time. It’s not clear exactly how much venom it takes to kill a human.
But based on the LD50 above, to kill an average person, you’d need about 7mg. However, some sources claim that all it takes is 1.5mg—a fraction of a teaspoon.
Beaked sea snakes are incredibly deadly, not just because of their venom, but their aggression too. The deadliest snakes on earth are always both venomous and aggressive. Concerning the number of deaths caused, nobody is exactly sure, but these snakes are responsible for most sea snake bites.
A paper in the Journal of Tropical Medicine and Hygiene, 101 patients with snake bites were examined. Of these patients, 80 were fisherman, and 90% were male. 8 of these patients died, and 7 of those had been bitten by the beaked sea snake.