| 1 | Virginia opossum |
The main opossum in the USA, inhabiting all 48 lower states, as well as most of Mexico and Ontario. The Virginia opossum can even inhabit the parched slopes of Texas and Arizona, and one reason why is a helpful resistance to the venoms of deadly rattlesnakes.
The western diamondback rattlesnake is the most common rattler in the southern US, and causes the most human fatalities of any US snake. Ordinarily, small mammals are their top prey, but the Virginia opossum has a peptide in its bloodstream which deactivates the toxins. They’re immune by their very nature, taking painful bites and fleeing into the bushes at top speed, when the overconfident rattlesnake expects them to roll over and die.
One study injected mice with a Virginia opossum serum, and found that they too become immune to rattlesnake venom. Virginia opossums are even resistant to the Russell’s viper of India, despite the two species living thousands of miles apart. Scientists have wondered whether they could extract this opossum peptide and turn it into a marketable snakebite shield.
Virginia opossums aren’t immune to all venoms. A large 1976 study injected them with Indian cobra, cape cobra and Chinese cobra venom, and triggered the usual slow death. But they did survive venom injections from eastern diamondbacks, cottonmouths and copperheads.
| 2 | Mongoose |
Quite possibly the boldest, cockiest snake-resistant animal of all. The mongoose doesn’t just flee from the sight of cobras – it hunts them across the parched African savannah, for their tasty serpent meat.
Mongooses have the initial ability of extreme speed, allowing them to effortlessly weave between a cobra’s lunges. Over the ages, their eyes have adapted specifically to cope with snake-style manoeuvres. Even if mongooses fail to dodge, which they occasionally do, they have venom resistance as a backup. They can take a bite from a forest cobra, red spitting cobra or Egyptian cobra without succumbing to their merciless toxins.
The precise resistance method is different to Virginia opossums. Instead of antivenom peptides flowing through their bloodstream, mongooses have evolved a different shape of acetylcholine receptor in their muscle cells.
Ordinarily, cobra neurotoxins bind to these receptors and disrupt brain signals which control muscle contraction and relaxation. The result can be total paralysis. But with the mongoose, these snake-borne neurotoxins simply bounce off the receptors, like an incorrect jigsaw piece that can’t be rammed in no matter how hard you push.
| 3 | Savannah monitor |
A slow, bulky reptile which rarely exceeds 1 metre. The savannah monitor is a species of central and western Africa, including Nigeria, Ghana, Togo and Benin. Its lifestyle involves plodding slowly around the countryside all day, taking its time. It tends to live in cobra-heavy environments, the same environments where mongooses often beat up those cobras.
However, the option of fleeing at high speeds, an option open to so many animals, is simply not possible for the savannah monitor. So instead, this thick reptile evolved a more effortless defence: venom resistance, particularly against the alpha-neurotoxins of cobras. It’s the only Varanus reptile member to be resistant, as this study found no resistance in the closely related komodo dragon and perentie.
Remember the acetylcholine receptors in muscles we just discussed? The amino acids in them have a natural negative charge. Therefore, cobra neurotoxins have evolved over the ages to have a strong positive charge, to be drawn to these receptors like a magnet.
In other monitors, the receptors have the usual negative charge, but the savannah monitor is the lone exception. Consequently, less neurotoxins manage to bind per bite, allowing the savannah monitor to withstand far more cobra venom without succumbing to paralysis.
| 4 | California ground squirrel |
This burrowing squirrel is so common in California that locals walk past it without bothering to think. At first glance, there’s nothing exceptional about this furry creature, yet one secret fact uncovered since the 1970s is their resistance to rattlesnakes, particularly the northern Pacific rattlesnake (Crotalus oreganus).
This common rattler has a necrotic venom rich in metalloproteinases. It’s a mammal eater, yet the California ground snake squirrel can take a fully fledged bite without convulsing and dying. Not only that, but the squirrel will often stand its ground, pummeling down furiously on the confused rattlesnake’s back, and even throwing pebbles in its face. Sometimes, the squirrel wins the battle after being bitten; researchers have had to drag the poor snakes clear before.
The more rattlesnakes live in an area, the higher resistance the local squirrels have. A 1987 study injected California ground squirrel serum into mice, and found that those from Sunol and Winters (both rattlesnake havens) increased the mice’s resistance to the venom, transferring the shield across.
Meanwhile, serums from the Sierra Valley north of Truckee, which is relatively sparse in rattlesnakes, added no resistance. Neither did the serum of arctic ground squirrels from central Alaska.
| 5 | Honey badger |
The internet’s favourite savage furry pet, because there’s nothing cuter than a fluffy mammal which walks over to snakes and casually bites their heads off.
The honey badger of Africa (not a real badger) is immune to numerous snake toxins, including cytotoxins and neurotoxins. Like the mongoose, it possesses mutations in the nicotinic acetylcholine receptors of its muscles cells, morphing their shape and preventing alpha-neurotoxins from binding.
There are dozens of epic honey badger battles scattered across the web, including one duel involving a puff adder. This is a thick-bodied African serpent which can go weeks without moving.
In night-time shrubland lit only by the torchlight of researchers, a honey badger strolled up to the puff adder without a care in the world. For a while, the two circled each other cautiously. Eventually, the honey badger got bored, and unlike the careful, ninja-like mongoose, it just grabbed the puff adder and commenced eating.
In the process, the puff adder landed a bite, and the honey badger suddenly fell unconscious. It lay in a honey badger coma for two hours, but eventually its natural resistance kicked in. It brushed itself off, and finished eating its puff adder meal as though nothing had happened. Another battle involved an orange cape cobra, which a honey badger chased up a tree and forced to drop from a branch.
| 6 | European hedgehog |
The common hedgehog native to Britain, France, Germany, and many more. The European hedgehog has 6000 spines on its back, and is capable of shrinking down into a compact, indestructible ball. Another of their skills is venom resistance.
The hedgehog specifically evolved to cope with one snake – the adder (Vipera berus), which is found across most of Europe. Adder venom is loaded with powerful haemorrhagins, causing blood to pour from small wounds, but when these gain access to the hedgehog’s body, they find themselves deactivated and unable to unleash their usual mayhem.
In 1996, scientists discovered why – a molecule called erinacin in the hedgehog’s muscle tissue. This molecule is even active against snake species found thousands of miles away, including the Brazilian jararaca (Bothrops jararaca).
Despite their peaceful reputation, hedgehogs actually feast on small animals regularly, and adder meals have been regularly sighted. With this innate resistance, they have no fear of gulping down an entire venom gland in the snake’s neck and dying 6 hours later.
As well as haemotoxins, erinacin also deactivates metalloproteinases in snake venom, toxins which shred healthy tissues and cause necrosis. The European hedgehog is like a mini-spiked tank, with multiple layers of defensive armour.
| 7 | Blue-tongued lizard |
Of all venom resistant-creatures worldwide, the blue-tongued lizard might be the most focused and targeted. This species is named for its strongly blue tongue, but otherwise looks fairly normal. It’s grey-scaled, with short, stumpy legs and a thick muscular body. Without the ability to flee, it has evolved a helpful armour of venom resistance, but specifically against one species: the red-bellied black snake.
This species ranks 3rd for annual snakebites in Australia, behind tiger snakes and brown snakes. Its venom is filled with pro-coagulants, which warp prothrombin and deplete blood clotting factors. However, the blue-tongued lizard can walk away from a bite unharmed, and continue on as though nothing happened.
This was only discovered in 2021, and unlike erinacin in hedgehogs, the magic compound remains unidentified. Scientists theorised that the prothrombin in blue-tongued lizards could have been a special shape, but other Australian snake venoms warped it just as easily.
Therefore, it’s now believed that similarly to the Virginia opossum, blue-tongued lizards have special peptides in their bloodstream, only targeted specifically against red-bellied black snake toxins.
| 8 | Southern plains woodrat |
The western diamondback rattlesnake must be a very confused snake, as its prey keeps on developing resistance. The Virginia opossum is one such armoured prey, but in 1976, another resistant animal was discovered purely by accident: the Southern plains woodrat.
A student in the Texas A&M University was asked to feed a snake they were keeping, and threw across a captive woodrat. It was a mundane, everyday exercise, until the woodrat mysteriously survived the bite.
A comparison with mice followed in 1984, when the two species were given varying quantities of western diamondback venom. At 0.25 milligrams, the mice suffered massive internal haemorrhages and died, but it took 7.5mg before the woodrat suffered the same fate. Specifically, the woodrat is immune to the haemorrhagic activity of rattlesnake venom, rather than neurotoxins, which few rattlesnakes possess.
Neotoma micropus is called the packrat due to its habit of gathering things, particularly shiny items. Its snake venom resistance is shared by other Neotoma members, hinting that it originated long ago, before the individual species diverged. Other resistant members include the desert woodrat and white-throated woodrat.
| 9 | White-eared opossum |
This Brazilian opossum lives far away from its Virginia cousin. It’s an omnivore with a striped face and extremely hairy back, and most importantly, is confirmed to prey on venomous snakes.
The white-eared opossum (Didelphis albiventris) can go from eating passion flower and mulberries one minute, to tucking into a viper the next. Consequently, their body has evolved resistance to venom, and in particular, the phospholipase A2 (PLA2) class of toxins.
This is a common toxin type in snakes, known for cytotoxic powers that cause necrotic decay. However, Didelphis albiventris and the big-eared opossum are the only mammals with confirmed resistance. One of the bloodstream protection factors was discovered in 1996 and dubbed DA2-II.
A less resistant animal might just eat the snake’s lower body, but white-eared opossums always eat the head first. The first contact of their claws is usually with the back of the head. Their next move is to shake and toss the snake around violently until it gives up. Then the opossum commences eating, holding the body down with its foot. Snakes they eat include the Brazilian jararaca and non-venomous Liotyphlops beui.
| 10 | Central bearded dragon |
This leathery-looking reptile inhabits a wide chunk of central Australia. Its range touches almost zero coastline, but covers a large area of inner rocky deserts, plus some drier forests.
Central bearded dragons are excellent climbers, and are already afforded some protection from snakes by their spiky skin, which makes grabbing them difficult. However, they also have a handy venom immunity. This comes in a similar style to the Egyptian mongoose: resistance to paralysing alpha-neurotoxins, via an unusually shaped nicotinic acetylcholine receptor.
Like the savannah monitor, central bearded dragons are stiff and slow, forcing their evolutionary hand into resistance instead. One study tested Indian cobra (Naja naja) venom, a species which doesn’t live in Australia, but is loaded with similar alpha-neurotoxins. Compared to chicken embryos, the central bearded dragon embryos were able to cope with 5 times more venom. They also discovered a resistant fish, the three-spined stickleback (Gasterosteus aculeatus). This could cope with 10 times more venom than a zebrafish.
Other skills of the central bearded dragon include darkening its own skin colour, hissing loudly, and making small yet intimidating leaps toward a predator.