This kind of bird is called toothpick bird, and crocodiles don't eat it because they are in a game relationship, which is a survival rule of * * * relationship. The process of mutual game is actually a set of survival rules gradually formed in the evolution of nature, and the result of the game makes the law of life continue.
According to Selfish Genes, there are about 8,000 ~ 9,000 species of birds in the world, of which about 300 will help other animals clean up their bodies. For example, crocodiles and toothpicks are both Egyptian birds, and there is a mutually beneficial relationship between them.
After eating and drinking enough, the crocodile will open its mouth comfortably, let the toothpick bird fly into its mouth and help it clean up the food residue and parasites in its mouth. Even if the crocodile closes its mouth when the toothpick bird cleans its mouth, it will not swallow the toothpick bird in one gulp. The toothpick bird helps crocodiles clean their mouths to "have a full meal". It doesn't matter if the crocodile closes its mouth when the toothpick bird helps the crocodile clean up, because the toothpick bird knocks its teeth or mouth with its mouth, and the crocodile will open its mouth to let the toothpick bird out.
Toothpick bird is a bird with high vigilance. When the crocodile relaxes, the toothpick bird will not only clean the crocodile's mouth, but also keep watch for the crocodile. Once there is an enemy situation, the "guard" of the toothpick bird will give a warning to the crocodile to help it get out of danger.
The relationship between toothpick birds and crocodiles is called "biological relationship" by researchers. But this relationship does not conform to Darwin's theory of evolution, because when the toothpick bird concentrates on cleaning the crocodile's mouth, the crocodile can completely swallow the toothpick bird, but why not swallow the toothpick bird?
This is related to the laws of nature-the law of tit for tat.
Crocodiles don't eat toothpick birds, which is a survival strategy evolved from the game between animals in the evolution of nature.
If the crocodile eats the toothpick bird when picking its teeth, there will be little or no toothpick bird to help it pick its teeth in the future. In the long run, food residues and parasites in the crocodile's mouth will inevitably accumulate in its mouth, so that crocodiles are prone to tooth decay and even tooth loss. In addition, toothpick birds can be vigilant when crocodiles pick their teeth. If there is no toothpick bird to keep watch for it, crocodiles have to devote most of their energy to alert their surroundings.
After weighing the pros and cons, crocodiles will find it uneconomical to eat toothpick birds. Obviously, not eating toothpick birds is good for both sides, and this relationship has gradually formed.
In fact, it is not only between animals, but also between people. During the war, South Korea and North Korea once fought to the death for a highland, but in the end it was only a symbolic robbery, and it was common for highlands to change hands. This is not because they want to disobey orders, but because both sides suffered heavy losses in the process of looting in the highlands, and the division of North and South Korea also made it impossible for soldiers from both sides to return home, so there was a symbolic looting.
It can be seen that even hostile parties can form a tacit understanding in the process of natural evolution, and once this mutually beneficial tacit understanding is broken, both parties will pay a heavy price. If you are friendly to me, I will be friendly to you. If you betray me, I will throw a knife at you.