How is a mongoose immune to snake venom? They are not immune to all snake venom, just the snakes they live around. Even then, they have resistance rather than immunity.
There are different types of venom for different types of snakes. The mongoose is particularly resistant to the venom of the cobra, which is a neurotoxic venom. There are three types of snake venom: neurotoxic, hemotoxic, and cytotoxic. Neurotoxic venom attacks the brain and the nervous system, paralyzing or killing the prey. Hemotoxic venom targets the blood and stops it clotting. This can cause damage to the organs and internal bleeding. Cytotoxic venom attacks the cells and kills them. The mongoose is resistant to some neurotoxic venoms.
There are 23 different types of mongoose. Some are a little bit smaller and some a little bit bigger, but they are all generally about the size of a cat with short legs and a very long body. We are talking about snake venom, but snake is not the main thing that mongoose eat. They are opportunistic feeders in that they eat anything that they find. They are omnivores and eat birds, small mammals, reptiles (including snakes), insects, fruits, and plants. They eat eggs, and they have been blamed for the extinction of several different types of animals. They are famous for eating snakes, but they will eat anything that is in range and is easy.
So, how do they eat snakes? The snake that they usually eat is the cobra. Cobras grow up to several meters in length and they are famous for having a hood next to their head when they rear up. They are commonly used by snake charmers. They tend to hunt small mammals and they sneak up on their prey before biting it and injecting their venom. They are shy animals and they usually flee rather than fight. Mongoose use three methods to overcome and kill a cobra. The first thing is they are incredibly fast. Cobra are not the fastest of snakes, and they always draw back before they strike. Because of the positioning of their fangs, they have to strike downwards and all of this gives the mongoose plenty of time to get out of the way. They usually provoke the cobra into striking repeatedly until it is exhausted. Then the mongoose runs behind the cobra and uses its sharp teeth and very strong jaws to finish the snake off. The second thing is that they have tough hide. They are fast enough to avoid the snake’s strikes, but if they happen to be too slow, anything but an indirect strike would bounce off their hide And the third adaptation they have is they are resistant to neurotoxic venoms.
Neurotoxic snake venom has alpha-neurotoxin in it. All muscles cells have receptor molecules that are activated by acetylcholine, which come when the nerves send signals to the muscles to contract or relax. Alpha-neurotoxin can bind to these receptor molecules, which means they block them from the acetylcholine. If there are no signals coming to tell the muscles to contract or relax, the victim is paralyzed. If there is no antivenom, this paralysis will be fatal. Mongoose have developed a resistance to this alpha-neurotoxin. The shape of the receptors is different to that of other mammals and the alpha-neurotoxin from snakes cannot latch onto it. Snakes actually have this same adaptation in their own bodies so that they cannot be poisoned by their own venom.
This adaptation that mongooses possess helps them survive a cobra bite, but they are not immune. Some of the alpha-neurotoxins will stick and the mongoose can still get sick. They have enough resistance to survive a normal load of toxin from a normal bite. If they were bitten several times, or bitten by several cobras, they would probably die. They can also be killed by a King Cobra, which packs a more potent venom and more of it. They also wouldn’t stand a chance against the stronger snakes, such as pythons. They might be fast enough to keep out of the way, but if a python grabbed them, resistance to neurotoxins won’t do them much good. They also don’t have much chance against the faster snakes, such as the pit vipers. A rattlesnake is a pit viper and not only are they much faster than cobras, their venom is a hemotoxin, which is the one that stops the blood clotting. Mongooses are incredibly strong, and they can easily kill a cobra, but there are a whole world of snakes that they wouldn’t be able to kill, and two other types of venom that they are not resistant to. And this is what I learned today.
Photo by Omkar Vinchu: https://www.pexels.com/photo/selective-focus-photo-of-gray-mongoose-on-grass-2873591/
Sources
https://www.newscientist.com/article/mg15320642-500-science-mongooses-secret-is-to-copy-its-prey
https://animals.howstuffworks.com/animal-facts/mongoose-versus-cobra.htm
https://en.wikipedia.org/wiki/Mongoose