Is the Belcher’s Sea Snake the Most Venomous Snake in the World?

Is the Belcher's sea snake the most venomous snake in the world?

Hydrophis belcheri, common name belchers sea snake, sea snake venom?

Check out this answer from Consensus:

The venom of Belcher’s sea snake and its relatives is a complex mixture of proteins with diverse toxic effects. Research into the venom’s composition, toxicity, and the efficacy of antivenoms is essential for improving clinical outcomes following envenomation. As studies continue to unravel the molecular intricacies of these venoms, the development of more targeted and effective treatments becomes a tangible goal.


Belcher’s sea snake (Hydrophis belcheri), known for its potent venom, is a marine elapid snake inhabiting coastal regions. The study of sea snake venoms, including those of Hydrophis species, is crucial for understanding the pathophysiology of envenomation and developing effective antivenoms. This article delves into the composition and toxic effects of sea snake venoms, with a focus on recent research findings.

Sea Snake Venom Composition and Toxicity

Recent studies have shed light on the complex proteome of sea snake venoms. For instance, the venom of the spine-bellied sea snake (Hydrophis curtus), a relative of Hydrophis belcheri, has been extensively analyzed. The venom consists predominantly of phospholipase A₂ (PLA₂), three-finger toxins (3FTX), and cysteine-rich secretory proteins (CRiSP)1. PLA₂, in particular, is present in various homologues, with acidic subtypes being the most common. The 3FTX family includes short and long alpha-neurotoxins, which have been shown to be lethal in mice1.

Immunoprofiling and Antivenom Cross-Neutralization

The effectiveness of antivenoms is a critical aspect of sea snake bite management. The Sea Snake Antivenom (SSAV) from Australia has demonstrated the ability to cross-neutralize the venom of Hydrophis curtus, with varying efficacy against different toxin components. While SSAV shows strong immunorecognition towards PLA₂, it has moderate-to-weak recognition of alpha-neurotoxins, suggesting that improvements in antivenom formulation are needed1.

Transcriptomics and Toxinological Correlation

Advancements in next-generation sequencing have allowed for a deeper understanding of venom-gland transcriptomics. In Hydrophis curtus, 3FTXs are the most abundantly expressed toxins, with significant functional diversity. The transcriptomic analysis has also revealed other less-studied toxins, such as snake venom metalloproteinases and L-amino acid oxidases, broadening our knowledge of sea snake venom composition2.

Histopathological Effects of Sea Snake Venom

The myotoxic effects of sea snake venoms are a major concern. A study on the venom of Hydrophis cyanocinctus, another species within the same genus, has identified a myotoxic phospholipase A2 (PLA2-H1) that induces severe myonecrosis and histopathological changes in various organs of experimental animals. These findings highlight the potential systemic effects of sea snake venoms, including those of Hydrophis belcheri3.


Is the Belcher’s sea snake the most venomous snake in the world?

Bryan Fry has answered Unlikely

An expert from University of Queensland in Hematology, Evolutionary Biology, Toxicology

No it is not. In fact is has never even been tested. Not sure how this rumour got started but it is a persistent one.

Current top-10 LD50 rankings:

Species, Common name, Sub-cutaneous (mg/kg)

  1. Oxyuranus microlepidotus, Inland taipan 0.025
  2. Pseudonaja textilis, Eastern brown snake 0.0365
  3. Aipysurus duboisi, Dubois’s sea snake 0.044
  4. Pelamis platurus, Yellow bellied sea snake 0.067
  5. Acalyptophis peroni, sea snake species 0.079
  6. Oxyuranus scutellatus, Coastal taipan 0.106
  7. Bungarus multicinctus, Many banded krait 0.108
  8. Hydrophis melanosoma, Black banded sea snake 0.111
  9. Enhydrina schistosa, Beaked sea snake 0.1125
  10. Boulengeria christyi, Congo water cobra 0.12

More information and data found in my book “Venomous Reptiles and Their Toxins’ (


Is the Belcher’s sea snake the most venomous snake in the world?

José María  Gutiérrez has answered Unlikely

An expert from Universidad de Costa Rica in Biochemistry, Immunology

If overall toxicity of a snake venom is assessed by determining the Median Lethal Dose (LD50), i.e. the dose that kills 50% of injected animals, usually mice, the venom of Hydrophis belcheri is not the most potent venom among snakes. Although sea snakes like this one in general have highly toxic venoms, there are other elapid snake species, such as the brown snake (Pseudonaja textilis) and the taipan (Oxyuranus scutellatus) whose venoms are more toxic than that of H. belcheri


Is the Belcher’s sea snake the most venomous snake in the world?

Arno Naude has answered Unlikely

An expert from Snakebite Assist in Toxicology

To designate that status to a single species is not very reliable. We see very few if any bites on humans from this species of sea snake. Each human is an individual and each snake bite is different to any other snake bite even from the same specimen biting two people in a row. The snake that kills the most mice in an LD 50 test has never killed a human so we have no idea how bad it might be. We do speculate that the Inland Taipan would kill you the quickest but we are not sure of that as we have no data for human bites. Using the LD50 index is also not accurate. We use mice for the test and humans are not mice. For example a Sydney funnel web spider has no effect on most animals like dogs and cats but is lethal in humans. The venom of any snake changes in its life time from adult to baby, its geographical location, the sex of the snake as well as even what time of year the bite occurs. Due to all these factors picking one snake is irresponsible. However just bear in mind dead is dead. If you are shot with a shotgun or a .45 the effect could be the same (death) or not as bad (minor injury) depending on many factors as well. For this reason to pick any one snake is not scientifically justifiable.


Is the Belcher’s sea snake the most venomous snake in the world?

Timothy Jackson has answered Unlikely

An expert from University of Melbourne in Evolutionary Biology, Philosophy, Toxicology

The short answer is “no” – this is a common misconception that was created by the inappropriate comparison of toxicity testing methods and reported in a popular herpetological text book. All things being equal (i.e. when modes of administration are matched) the venom which is most lethal, by concentration, to lab rodents in controlled experimental conditions, is that of the inland taipan (Oxyuranus microlepidotus) from Australia. The qualifications (i.e. the use of lab rodents) mentioned above are important – this data reflects a “laboratory reality”, not an evolutionary or biological reality. It is also doesn’t necessarily reflect a clinical reality – despite being so toxic, inland taipans have never been responsible for a single human fatality on record. On the other hand, there are far “less venomous” species in India and Sub-Saharan Africa that are responsible for many thousands of deaths every year (see So really, the question of which snake is the “most venomous” is far less interesting and far less important than those concerning why snake venoms differ (i.e. what drives the evolution of diverse venom composition and activity) and why certain snakes cause so many serious and fatal bites to humans, whereas others cause relatively few.


Is the Belcher’s sea snake the most venomous snake in the world?

Daniel Dashevsky has answered Unlikely

An expert from University of Queensland in Herpetology, Biology, Evolutionary Biology

No, but let’s look at why.

These days, researchers define venom as a toxic secretion that is produced by one animal and delivered to another by inflicting a wound. Under this definition it’s not immediately apparent how an animal would be more venomous than another. Perhaps we could look at the amount of venom produced. There has not been an in depth investigation into the average venom yields from various species, but the experience of various snake venom production facilities suggests that the species with the highest average yield would probably be the eastern diamondback rattlesnake (Crotalus adamanteus).

Now what the video uses as its criteria for “most venomous” is venom toxicity which is a very sticky issue. Toxicity is a measure of how dangerous a given substance is per weight, or to rephrase, how little of it is necessary to kill something. The gold-standard study of snake venom toxicity was carried out in 1979 by the Commonwealth Serum Laboratory (which also produces Australia’s antivenom) and their study found that the inland taipan (Oxyuranus microlepidotus) was distinctly more toxic than any other snake. Other, less comprehensive studies have confirmed this finding.

That being said, there is an important limitation to this result: these tests were carried out on mice. We know that the toxins in snake venom are often tailored to that snakes prey; for instance, the venom of the brown tree snake (Boiga irregularis) is vastly more toxic to birds than to mammals like us. While taipans prey on rodents, many of the snakes they were compared against do not. It’s possible that a sea snake species could possess the venom that is most toxic to fish, but no one has conducted a study to find out. To further complicate the matter, how dangerous a snakebite is depends on more than the abstract toxicity of the venom. It also depends on how much venom is delivered, the physiology of the victim, and—perhaps most importantly—the quality and immediacy of medical care.

Because Australia has a combination of low population, widespread snake and snakebite education, and a high caliber medical system very few people die from snakebite and the inland taipan has not caused a single recorded death. On the other hand, Papua New Guinea which has similar snake species as northeastern Australia sees over one thousand snakebite deaths per year. Across the globe the most lethal snakes are not necessarily the most toxic snakes. So no matter whether you frame the question in terms of venom yield, venom toxicity, or overall danger to humans, Belcher’s sea snake is far from the top.


Is the Belcher’s sea snake the most venomous snake in the world?

Juan Calvete has answered Extremely Unlikely

An expert from Instituto de Biomedicina de Valencia in Molecular Biology

The rapid answer is “no”… if one defines “toxicity” as an absolute term, e.g., the amount of venom that on average kills a 20g mouse, a 75 kg human… There are other snake venoms with well documented higher toxicity, including the already mentioned Australian Inland Taipan, but also North American Crotalus tigris or African Naja haje, both with LD50s for mice (intraperitoneal or intravenous) below 0.1 mg/kg. In other words, the lethal dose of these venoms is about 1 microgram per 20g mouse. Possibly this lethal potency is similar in humans. On the other hand, if we define “toxicity” as the amount of venom needed to kill the snake’s natural prey, then we must admit that studies on marine snakes are very fragmentary and limited to a few species. However, the venom of the yellow-bellied sea snake, Hydrophis platura, from Costa Rica (LD50 for mice: 2.3 (i.p.)-3.9 (i.v.) μg/mouse) was highly toxic to sympatric marine and allopatric freshwater fishes: estimated LD50 values by the i.p. route were 0.11 μg/g for L. guttatus; 0.26 μg/g for C. atrilobata; and 0.089 μg/g for D. maculatus. Therefore, we can conclude that the statement that “the Belcher’s sea snake is the most venomous snake in the world” is incorrect.

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