Some do it stealthily, others with terrifying gusto. There are those that crush, slice or inject their victims, drain their blood or dismantle them piece by piece. And sometimes you don’t even know it’s happened at all until it’s too late. Here’s our pick of the animals you really don’t want to get bitten by.
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Deadliest bites in the animal kingdom
Blue-ringed octopus
This diminutive cephalopod – just a few centimetres long – is surely among the most drop-dead gorgeous of all the animals that can lead to you dropping dead.
Its bite, delivered by a needle-sharp beak tucked away on the animal’s underside, is said to be painless. The first that some human casualties know about it is when symptoms appear after a few minutes: nausea, difficulty swallowing, walking and breathing, creeping paralysis.
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The blue-ringed octopus’s bite delivers a venom called tetrodotoxin (TTX), which is produced by bacteria living in the salivary glands. TTX is also found in the internal organs of pufferfish, which is why the Japanese delicacy fugu must be prepared with meticulous care.
TTX interferes with the passage of nerve impulses between brain and body, and eventually causes paralysis of the diaphragm and death by suffocation. There is no antidote. The only treatment available involves ventilating victims artificially until the TTX has been eliminated from the body.
It is widely claimed that a single octopus carries enough TTX to kill 26 adult humans. However, the origin of this statistic is mysterious, and it seems unlikely given that a typical octopus contains about half the lethal dose for a typical adult human. Certainly, fatalities are vanishingly rare. There are just a couple of confirmed cases in the medical literature.
Should you ever encounter a blue-ringed octopus, its exquisite colours are best marvelled at from a distance. And whatever you do, don’t pick it up. Statistically, eating pufferfish is far more dangerous than rockpooling in the west Pacific. Each year, about 30 cases of fugu poisoning occur in Japan alone and a few of those prove fatal. In a sense, a bite of a pufferfish can be deadly, too.
Vampire Bat
They may enjoy a strictly liquid diet, but vampire bats still need to bite. Native to Central and South America, all three species specialise in drinking the blood of living mammals and birds, including humans.
They hunt at night, when their victims are likely to be asleep, homing in on their warm-blooded prey with the aid of heat-sensitive organs on their face. Unusually for bats, they are agile on the ground as well as in the air, and scuttle around in search of a blood vessel that they can get their exquisitely adapted teeth into.
They slice through the skin using their razor-sharp upper incisors. The prominent canine teeth – the tool of choice among vampires of the fictional variety - serve only as a tripod to stabilise the bat against its victim while it operates. Anticoagulants in the saliva stop the blood from clotting, allowing the bat to lap it up as it flows from the wound.
The bite itself is fairly harmless, but a proportion of vampire bats harbour the rabies virus, which can be transmitted when they feed. Now that most dogs in South America are vaccinated against rabies, bats are the major source of human rabies infections on the continent.
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Black widow
It’s unfortunate that black widows like to live in the same places we do. In most parts of the world, one or other of the various species are prone to lurk in the darkest, dustiest corners of human habitations.
They rarely bite people, but when they do, the consequences are not to be sniffed at. The venom is a powerful cocktail of neurotoxins that induces over-stimulation of the nerves and muscles. Human casualties suffer cramping, racing heartbeats, excessive sweating, agitation and anxiety and, occasionally, in males, painful, sustained erections.
The vast majority of patients recover within a few days, and anti-venom is effective in the most serious cases. Deaths are now vanishingly uncommon worldwide.
It may not be just bad luck that the venom is so toxic to humans. Black widows have a knack for catching prey that is much larger than themselves. They build their haphazard 3-dimensional webs low down and connect them to the ground with unusually sticky vertical threads that are strung under high tension, so that any crawling prey that stumbles into them gets hauled up off the ground before it can run away.
This pulley system can immobilise animals hundreds of times the weight of the spider – mice, rats, snakes and lizards.
Indeed, vertebrates seem to form part of their normal diet, and one of the neurotoxins in the venom, α-latrotoxin, targets them specifically. If black widows built bigger webs, we might be in serious trouble.
Boomslang
There’s no shortage of snakes out there that can do you a mischief if they manage to sink their fangs into you. And in the case of the boomslang an arboreal species of sub-Saharan Africa, we have a rare and detailed first-hand account of what it’s like to be bitten by one.
Karl P. Schmidt was a herpetologist at Chicago’s Field Museum of Natural History who, in 1957, was bitten on the thumb by a boomslang that he’d been asked to identify. Very little was known at the time about the venom’s effects on the human body, so he started diligently taking notes.
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They make for harrowing reading: “Bleeding of mucous membranes in the mouth began about 5:30pm, apparently mostly from gums... Urination at 12:20am mostly blood... A good deal of abdominal pain, continuing to 1:00pm, only adequately relieved by belching.”
The next morning, Schmidt phoned the museum to tell them he was feeling perkier and would be back at work the following day. But by 3pm he’d died of respiratory failure.
Great white shark
Sure, you’re statistically more likely to be killed trying to take a selfie. But the fact is that sharks do bite – and kill - people with some regularity. In Australia alone, there have been 21 fatal attacks since 2020, according to the Australian Shark-Incident Database, and at least 15 of those involved a great white.
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This generalist predator of fish, marine mammals, seabirds, squid and turtles can nudge 2 tonnes in weight and 6m in length, and is equipped with 50-odd serrated teeth capable of ripping through skin, flesh and bone. It can bite with a force of 1.8 tonnes while thrashing its head from side to side to maximise damage.
Most attacks on humans are abandoned after just a single bite, which supports the idea that they are the result of mistaken identity. Because, let’s face it, if a great white wanted to eat you, it just would.
Komodo dragon
The world’s biggest living lizard, at up to 3m long and 100kg in weight, is an aggressive, slavering, opportunistic predator and scavenger famous for swallowing goats whole.
A Komodo dragon’s mouth is packed with up to 60 serrated teeth which it wields in a ‘grip and rip’ mode of attack. Any prey that escapes the initial onslaught may die more slowly of blood loss and the effects of the venom contained in its saliva.
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Native to a handful of Indonesian islands, dragons attacked 24 people on Komodo alone between 1974 and 2012, killing five of them. Many attacks take place when victims are answering a call of nature in the bushes.
The Komodo dragon is one of only a few species of lizard that deliver venom in their bites. Another is the gila monster, a chunky, black and orange denizen of the deserts of southern North America. Youtuber Coyote Peterson, who has allowed himself to be stung and bitten by a host of venomous animals, describes his encounter with a gila as “the worst animal bite of my life”, likening the pain to “hot larva coursing through your veins” Fortunately, fatalities are rare.
The death in 2024 of a 34-year-old US man after he was bitten by his pet Gila monster was the first to be recorded for around a century.
Mosquito
In itself, a mosquito bite is little more than an inconvenience - an itchy spot that will disappear after a few days. Unfortunately, mosquitoes carry a host of deadly pathogens that they can transmit while sucking human blood, including malaria, dengue fever, yellow fever, Zika virus, chikungunya, and West Nile virus. By this route, mosquitoes kill hundreds of thousands of people each year - more than any other animal by a long way.
Many different species of mosquito contribute to this total. One species, though - Anopheles gambiae of Sub-Saharan Africa - stands out as a particular threat due to its disproportionate role in the transmission of malaria, which kills over 600,000 people each year, most of them children. That said, a top ten list of the world’s most deadly animals would probably contain nothing but various species of mosquito. Don’t forget your insect-repellent.
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Nile crocodile
It’s not the biggest of the crocodilians (that honour goes to the saltwater crocodile of Australia and Southeast Asia). Neither does it have the most powerful bite (that, too, would be the saltie). What sets the Nile crocodile apart is that it is responsible for more human deaths than any other crocodilian.
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Attacks on humans across Africa are thought to exceed 300 per year, of which more than 60 per cent are fatal. In Zimbabwe, the species is responsible for more human deaths than all other wild animals combined. Many of these occur during the dry season when both predator and prey are reliant on dwindling water sources.
Like many of its relatives, the Nile crocodile grabs its victim in its jaws, drags it into the water to drown it, and then dismantles it by holding it tightly and rolling vigorously in the water – a manoeuvre known as the ‘death roll’.
Greening’s frog
Amphibians tend not to be feared for their bites. The paucity of teeth has something to do with it. Many have no teeth at all, and among those that do, they tend to be small, simple, peg-like things. What are they going to do? Gum you to death?
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That said, the Argentinean horned frog, a spherical, wide-mouthed ambush predator (also known as the Pac-Man frog for obvious reasons) is capable of delivering a painful bite. It’s big enough to take small mammals and birds, and will happily have a go at any human hand that’s offered to it. It can bite down with a force of 500 Newtons, which would feel like a teenager standing on your finger. And once clamped on, it’s reluctant to let go.
But it’s not exactly deadly. Greening’s frog is more dangerous, as a Brazilian herpetologist discovered in 2015 when he found himself on the receiving end of its venom (which has since been found to be twice as potent, measure for measure, as that of a pit viper) and experienced 5h of intense pain in his arm.
However, it might be stretching things to describe the frog’s defences as a venomous bite as such. The venom is delivered by small bony spines on the skull, which push through the frog’s skin when pressure is applied. They are situated around the mouth, but also on the back and top of the head, and there is no evidence that the frogs actively bite assailants. Rather, envenomation may occur passively when the frogs are handled roughly.
Piranha
Going by the horror films, you dip a toe into an Amazonian tributary and, before you know it, your flesh is being stripped from your bones by pack-hunting carnivorous fish.
The name ‘piranha’ covers several related species of South American freshwater fish. As a rule, they are opportunistic omnivores rather than specialist carnivores –they eat vegetation, nuts, fruit, seeds and carrion as well as live prey.
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With razor-sharp teeth and an immensely strong bite for their size (no species exceeds 50cm in length), they are quite capable of taking a chunk out of a swimmer or snipping off a digit.
Whether they ever kill humans is another matter, though. They do form shoals, but this seems to be more about seeking safety in numbers than pack-hunting. There are a few documented cases of human bodies being eaten by piranhas. But it’s always hard to know if the victims were already dead when the piranhas found them.