Sea snake attacks diver, is it because it is "blinded by love"?

Sea snake attacks diver, is it because it is "blinded by love"?

author:

Dai Li, PhD in Marine Ecology, Institute of Oceanology, Chinese Academy of Sciences

Audit:

Zhang Shanshan

Associate Professor of Marine Ecology, Quanzhou Normal University

In 2021, an interesting study was published in Scientific Reports, saying that in the waters near Australia's Great Barrier Reef, the highly venomous olive sea snake (Aipysurus laevis) frequently "attacks" human divers during certain periods.

Why do sea snakes attack people? Are they dangerous? Let's talk about sea snake attacks on humans.

Venomous sea snake

Sea snakes are a large family.

In a broad sense, sea snakes belong to the subfamily of the family Cobra, which includes more than 30 genera. However, the sea snakes we generally understand are those that live in the ocean in the subfamily of the family Cobra, and there are a total of 6 genera of these sea snakes.

And seeing that their family is "cobra", you will definitely immediately associate them with being extremely poisonous. Yes, many members of the sea snake family are venomous. Some of them are quite venomous, no less than cobras on land.

This is actually easy to understand.

The marine environment is very different from the terrestrial environment. On land, after a venomous snake bites its prey, it can follow the scent information left by the prey all the way, slowly waiting for the prey to die from the poison, and then eat them. So even venomous snakes with less venom have a chance to survive.

But the situation is quite different in the ocean. If the venom of sea snakes is too weak, after they bite their prey, the injured prey may also run a long distance, and it is difficult for sea snakes to follow their prey all the way.

As the prey escapes, they may be "taken advantage" by other predators, so in the harsh environment of the ocean, many sea snakes have evolved highly toxic venom. Those with less toxic venom may have evolved the ability to ambush.

The olive sea snake mentioned above is a highly poisonous sea snake.

Olive sea snake, Image source: Wikipedia

In addition, although sea snakes live in the ocean, they breathe with lungs like snakes on land, so they have to float to the surface of the water from time to time to breathe, and they also like to live in coral reefs with abundant food. So it is easy for them to encounter human divers.

The good news is that although sea snakes are highly venomous, they are relatively docile when facing humans and they will hardly attack humans. Because venom is also very valuable to sea snakes, they will not waste venom on prey that they cannot swallow. Sea snakes will only attack for self-protection when their own safety is threatened. So if you see a sea snake while diving or swimming in the sea, don't be too scared.

"Clingy" sea snake

Since sea snakes have such good tempers, why does the study at the beginning mention that sea snakes actively "attack" humans?

In fact, the attack here does not mean that the sea snakes really attack with their fangs. Instead, these sea snakes will suddenly pounce on divers and even wrap their bodies around the divers' arms and legs. This behavior is also "unusual" for sea snakes.

Because for sea snakes, when they see a "giant" like a human, their instinctive reaction should be to run away instead of rushing towards humans.

Although the sea snakes did not bite the divers with their fangs and did not cause any casualties, the divers would still be scared to death watching these more than one-meter-long and highly venomous creatures swimming towards them.

Why do sea snakes suddenly become so clingy? To find out, scientists analyzed the sex of the clinging sea snakes and the time when the clinging incidents occurred.

The results showed that during the sea snake's breeding season, this type of sea snake's active approach incidents occurred more frequently.

In comparison, male sea snakes are more likely to actively approach humans than female sea snakes. Even if females approach human divers, most of them will only approach once. Only males will come up repeatedly to "approach" humans.

The number of times sea snakes of different genders actively approach humans, with male sea snakes being more likely to actively approach humans. Image source: Reference 1

After getting close to humans, male sea snakes also stay around humans (or on their bodies) longer than females. Male sea snakes will even lick divers' clothes with their tongues after getting close, but female sea snakes rarely do this (divers who are afraid of snakes will probably be scared to death on the spot).

Combining these analyses, the researchers speculated that the reason why male sea snakes get so close to humans may be that they mistake humans for female sea snakes, or they mistake humans for the hiding place of female sea snakes.

It is understandable that a female sea snake would mistake a human for its hiding place, but the size difference between humans and female sea snakes is so great, how could a sea snake even get this wrong?

This is actually related to the eyesight of sea snakes. Snakes' eyesight is not very good, and sea snakes' eyesight is worse than that of land snakes. Olive sea snakes have pretty good eyesight. There is a sea snake called Emydocephalus annulatus, which sometimes mistakes sea cucumbers for their courtship objects, which is quite funny.

Sea snakes need to rely on sexual information molecules on each other's bodies to distinguish each other. However, these molecules are not water-soluble, so they are difficult to perceive from a distance. Sea snakes must get close to each other to recognize each other.

So when these sea snakes see humans, they will approach to find out what the heck is going on. Most female snakes approach humans for this very reason.

When a male snake approaches a human, it will also touch the human skin with its tongue, using the smell to determine if it is a female sea snake. During the breeding season, in line with the principle of "not missing any opportunity to fall in love", some sea snakes will wrap their bodies tightly around divers as soon as they come up. This action is also used by them to prevent females from escaping during mating.

Of course, sometimes female sea snakes want to reject male sea snakes and will look for places to hide. If they see divers swimming over at this time, they will quickly hide on the divers. This can also explain why the same female sea snake will generally only approach humans once in a short period of time.

However, when the male sea snake sees the female running away, it will search everywhere. Even if the female sea snake is not on the human, the male sea snake will come over to check again and again.

Therefore, these male sea snakes that actively approach humans are really "blinded by love."

Of course, it should be noted that these are speculations based on the behavior of sea snakes. Whether this is actually the case still needs further research and confirmation.

Based on these speculations, the researchers also gave suggestions for what to do when encountering a sea snake "attack".

If divers see sea snakes swimming towards them, they should never attack them, let alone forcibly pull the sea snake down. Otherwise, sea snakes would not attack humans in the first place, but may bite people in self-protection due to these stimuli.

Don't even try to escape, because it is unlikely that a diver can outrun a sea snake, and the act of running away may cause the male sea snake to mistake you for a female sea snake that is rejecting its courtship, and may continue to pester and chase you.

The best thing to do is to open your body and let them check it out. Once the sea snake realizes it has made the wrong target, it will naturally go away.

References:

[1] Lynch TP, Alford RA, Shine R. Mistaken identity may explain why male sea snakes (Aipysurus laevis, Elapidae, Hydrophiinae) “attack” scuba divers[J]. Scientific Reports, 2021, 11(1): 1-7.