Cobras are venomous snakes found in Africa, Asia and some parts of the Middle East. Their venom contains neurotoxins that can cause paralysis and death in many animals. However, there are a few animals that have developed immunity or resistance to cobra venom over time.
The Mongoose
The mongoose is best known for its ability to fight and kill venomous snakes, including cobras. Mongooses have evolved physiological and behavioral adaptations that allow them to resist the effects of cobra venom and attack the snake before it can strike.
On a physiological level, mongooses have acetylcholine receptors that are insensitive to snake neurotoxins. Acetylcholine is a neurotransmitter that is important for muscle contraction. Cobra venom contains toxins that block acetylcholine receptors, causing paralysis and respiratory failure. Mongooses’ altered receptors prevent the neurotoxins from binding and taking effect.
Mongooses also have special neutralizing factors in their blood serum that inhibit the activity of snake venom toxins. These neutralizing factors bind to and inactivate toxins like neurotoxins, cardiotoxins and hemorrhagic components in cobra venom.
Behaviorally, mongooses will irritate and harass a cobra until it exhausts its venom in fruitless strikes. The thick coat and loose skin of the mongoose also serve as protection. After dodging the snake’s strikes, the quick mongoose will finally kill the cobra with a precise bite to the head.
The Honey Badger
The honey badger has gained notoriety as perhaps the most fearless animal in the animal kingdom due to the videos showing it confronting lions and venomous snakes. Like the mongoose, the honey badger seems to possess some innate physiological resistance and behavioral adaptions that allow it to hunt, kill and consume venomous snakes, including cobras.
Researchers have found that honey badgers have slightly lower sensitivity to various snake venoms when compared to other mammals. Their blood serum also contains cytotoxins and neurotoxins similar to those found in snake venom, suggesting the badgers have evolved the ability to synthesize their own venom components to increase tolerance.
Honey badgers seem to be able to resist the cytotoxic effects of cobra venom through unknown physiological mechanisms as well. When bitten, they do not show the swelling, necrosis and incapacitation seen in other mammals exposed to cobra venom.
Behaviorally, the aggressive honey badger relies on its loose, thick skin and swiftness to defend against snake strikes until the opportunity arrives for it to overwhelm and kill the snake. The honey badger’s endurance allows it to wear down even the most venomous snake.
Secretary Birds
The secretary bird is a large African bird of prey that feeds on snakes, including venomous cobras. Secretary birds are not totally immune to snake venom, but they have some adaptations that allow them to hunt, kill and eat venomous snakes:
- Thick scales and feathers on legs and head act as protection against bites.
- Long claws allow them to stomp and kill snake without being bitten.
- Snake venom does not seem to quickly incapacitate or kill secretary birds.
Secretary birds will find a snake in the grass, stomp it to death with their feet, then pick up and eat the dead snake. They carefully avoid the head to minimize being envenomated. While not totally immune to venom, the secretary bird’s size and defenses give it resistance and allow it to feed on venomous cobras and other snakes.
California Ground Squirrels
California ground squirrels have developed resistance to venom from Northern Pacific rattlesnakes, which prey on the squirrels. Resistance seems to come from mutations in the squirrels’ acetylcholine receptors that prevent binding of snake neurotoxins.
In laboratory tests, California ground squirrels exhibited significantly higher resistance to venom from rattlesnakes and some other vipers compared to non-resistant rodents. While not immune, their adaptations give California ground squirrels important defenses against predator snakes.
Fox snakes
Fox snakes typically prey on small mammals like mice, but they are known to also eat venomous snakes on occasion. Researchers have found that fox snakes have serum factors that neutralize viperid and elapid snake venoms to varying degrees. Fox snakes show high levels of resistance to Eastern Massasauga Rattlesnake venom in particular.
Fox snakes can kill and consume rattlesnakes and possibly cobras due to serum neutralization and factors like thick skin and rapid onset of symptoms. However, they do still show incapacitating effects when significant amounts of venom are injected.
Hedgehogs
Hedgehogs have some natural protection and resistance when it comes to snake venoms. Their thicker skin and dense coat helps prevent fangs from injecting venom deeply. They also have a layer of fat under their skin that limits venom spread.
Some research indicates hedgehogs also produce a protein called erinacin in their liver which has anti-hemorrhagic properties against snake venom toxins. The combination of these adaptations allows hedgehogs to exhibit resistance to adder and viper snake venoms.
Pigs and Pot-Bellied Pigs
Pigs and related animals like pot-bellied pigs demonstrate some resistance to venomous snake bites, including rattlesnakes and cobras. The layer of fat under their skin can limit venom spread from a bite.
Pigs may also utilize their own antibodies and immunization responses to neutralize or counteract snake venom toxins. Pot-bellied pigs have survived cobra bites when given good medical care, though severe bites still have the potential to be lethal over time.
Opossums
Virginia opossums have shown resistance to venom from rattlesnakes and cottonmouths. Opossum serum contains small peptide toxins that can neutralize snake venom by binding to venom components.
Opossums also have lower sensitivity to snake venom at receptor sites, which protects them from the neurotoxic effects that can paralyze and kill other animals. These adaptations allow opossums to survive significant snake bites from vipers and possibly even cobras.
Non-Venomous Snakes
Many types of non-venomous colubrid snakes, like garter snakes and water snakes, exhibit resistance to the venom of vipers and elapids, including cobras. Blood serum from these snakes can even be used to create antivenom.
Colubrid snakes possess adaptations like venom toxin-inhibiting serum factors and alterations of receptor sites to prevent venom binding. Their non-lethal venom may also enhance their immunological resistance. These mechanisms allow them to hunt, kill and consume venomous snakes with limited ill effects.
Snake handlers
Through gradually increasing exposure to snake venom, snake handlers can develop some resistance to otherwise lethal doses of snake venom. This limited immunity comes from the production of neutralizing antibodies and alterations in cell receptor sites.
However, natural snake handler immunity only works against the specific venom types and doses handled by the individual. Antivenom treatment is still essential in case of severe envenomation. No snake handler can ever become fully immune to cobra venom effects.
Conclusion
In summary, a number of animals have evolved impressive resistance and even immunity to the venom of snakes like cobras. This ability allows them to hunt, kill and consume venomous snakes with limited ill effects.
The mongoose, honey badger, secretary bird, California ground squirrel, fox snake, hedgehog, pig, opossum and various colubrid snakes all possess adaptations like toxin-neutralizing blood factors, venom-resistant receptor sites, protective skin and rapid onset of symptoms that provide significant defense against cobras. However, no animal is totally immune to the devastating effects of a severe cobra bite.