Live Wilderness Adventure

Chapter 865 Levi's Flight

In front of the narrow opening, Bi Fang identified the animal footprints coming and going.

Some of these footprints have been preserved for quite a long time.

The surface of the African prairie in the dry season is dry and hard, and footprints are rarely left, unless it is a giant reptile like the Komodo dragon, whose sharp claws will leave a trail on the hard ground under the action of its huge weight Row of small holes.

Most of what everyone saw at the entrance of the cave was left by the wet season.

However, there are fresher footprints, paw prints, and hoof prints in the cave.

No large carnivores.

After watching for a long time, Bi Fang confirmed the matter.

Then he checked the surrounding environment and confirmed that within a certain range, there was only one entrance to this underground river, so he took Harley to hide behind a pile of rocks, preparing to wait for a while.

Bi Fang sat on the ground against the stone and polished his spear.

The quality of human life has been greatly improved in recent decades - tall buildings, bustling streets, beautiful night scenes, these are no longer new things.

The rapid development of technology has made our life taste more and more high, and things that were considered luxuries in the past are now easily achievable.

For three meals a day, we are no longer just seeking to satisfy our hunger, but have higher quality requirements for taste. We pursue 'food'.

However, for the wild animals who also inhabit the earth, filling their stomachs is still their primary contradiction.

Herbivores or omnivores are fairly optimistic, and their food sources are relatively abundant. As long as they are not born in deserts or places like the Gobi Desert, there is always something to eat.

The requirements for carnivores are relatively high. They must hunt to obtain food.

During the hunting process, the predator needs to fight wits and courage with the prey, which is a double test of energy and physical strength, and even if the hunting is successful, the food obtained cannot be preserved for a long time, and there is even a risk of being robbed.

【Cheetah: Raise your hands in agreement】

【Cheetah: That’s right】

[Why @cheetah (狗头)]

[If there is discrimination, you can speak out, everyone, hahaha]

【Harley: What B netizen】

Bi Fang carried the polished spear on his back, and then looked for some plants with a strong smell nearby to cover up his figure.

Perhaps because of the proximity to the water source, the plants growing in the crevices of the rocks are all green, much more vibrant than the bright yellow dry grass seen on the grassland before.

One of the main tasks of our trip to the African prairie this time is to teach Harley how to hunt, so that he doesn't become a fool when he lives alone on the prairie and can't even eat meat.

However, different types of predators have different temperaments, tastes and physical conditions, and their predation styles are naturally different. We also need to demonstrate according to the characteristics of the animals themselves.

For example, the difference in predation styles between lions, tigers and wolves reflects the difference between cats and canines.

Lions and tigers are very strong and agile, and the latter prefer to walk alone; gray wolves are weaker in stature and speed than lions and tigers, but living in groups greatly improves the predation efficiency of gray wolves.

When Canadian gray wolves are catching bison, in the natural environment covered by ice and snow, they will constantly use double-team harassment tactics to make the bison herd into chaos, waiting for an opportunity to attack the bison that is alone.

Like Big Big Wolf, it is very rare that he wants to wipe out Yangcun on his own.

[This is a good example]

[For example, Lao Fang has always been able to]

Compared with wolves, tigers, as cats, are much more arrogant. Even among the lions that hunt in groups in the public impression, there are many male lions and a few female lions who like to act alone.

Feline hunting pays attention to ambushes, and it is fast and accurate. Even if the cheetah is the king of speed, it can catch up with hard pursuit in many cases, but it is actually an extra cost. Ambush is the best choice.

So, the focus of our demonstration is on the ambush.

However, a clever woman can't cook without rice. No matter what strategy is adopted, the predation action needs to have a major premise, that is, to be able to find the prey first, otherwise, no matter how strong the predation ability is, it is just empty talk.

For wild animals, the most natural foraging strategy is to simply follow Brownian motion and Levi's flight.

Brownian motion?

Levi's flying?

When Bi Fang was talking about how to find prey, he suddenly heard a physics concept, and many viewers were a little confused.

[What the hell is Brownian motion? 】

[Brownian motion is irregular, right? No matter how you look at it, this is not quite right with Fang Shen's thinking. Didn't you always look for traces and traces in the past?]

[So, can anyone tell me what Levi's flight is? 】

【I don't read much, tell me quickly】

That's true, but the one who looks for traces, traces, and finally discerns the direction is me—a human being.

For animals, it's too much of a brain test to grasp these things explicitly.

Most animals at the top of the food chain, such as lions, tigers, wolves, eagles, crocodiles, etc., actually rely mainly on vision to find prey.

There is no gradient difference in visual signals, invisible is invisible, and no animal has clairvoyant eyes.

Raptors like eagles have a wide field of vision and don't need to go to great lengths to forage, but land animals like lions and tigers have to think about foraging strategies.

Brownian motion is the most natural approach without knowing the exact location of the prey.

But before Bi Fang finished explaining, the audience was even more confused.

[I'm not sure about lions, tigers, etc., but don't wolves rely on their sense of smell? How did it become visual? 】

[My cognition has been greatly challenged]

[Is it because the water in the underground river is so poisonous that Fang Shen is confused after drinking it? 】

【Are you lying to me】

For a moment, the bullet screen was full of voices of questioning or questioning.

Hey, in fact, everyone knows too little about the world of smell.

Bi Fang scratched his head, after all, the audience did not have the same keen sense of smell as him.

The gap in perception makes everyone seem to be separated by two worlds.

After thinking for a while, he gave an example that he thought was more appropriate.

Let's put it this way, if you put an alarm clock in a room on the second floor of a villa, and you sit in the living room on the first floor, can you accurately judge which room on the second floor the alarm clock is in just by hearing it?

I think most people can't do it. In the animal world with a keen sense of smell, their sense of smell plays the same role as our sense of hearing at this time. They know that the prey is on the second floor, but they don't know In which room, and smell is more ambiguous than hearing.

As long as you stay in one place for a long time, you can create two birthplaces with strong smells, which cannot be done in the world of sound.

[A little confused, but I feel like I've caught something again (cover my face)]

[seems to make sense]

【unclear feeling】

Everyone should be familiar with Brownian motion, the never-ending random motion of particles suspended in liquid or gas, a continuous random process.

In fact, Brownian motion may seem inconspicuous, but its discovery is a major development in physics, which has had a huge impact on human understanding of the universe.

The behavior of many creatures in nature also obeys this invisibly. Animals performing Brownian motion are like coming to the second floor, randomly entering a room to search, and from the perspective of data, this is still the most efficient one. kind of way.

Its step size obeys a normal distribution, just like random walk, its step size and direction are discrete. Although Brownian motion and random walk are two concepts, they have developed a different set of theories. But the mathematical essence of both is the same, no matter which foraging strategy a predator uses, there is virtually no difference in the efficiency of finding prey.

But if predators really do Brownian motion aimlessly like headless flies, can they really find their prey effectively?

Bi asked the audience questions.

You don't need to answer to know that the answer is no.

It can be proved mathematically that Brownian motion is the same as the free diffusion of molecules. The molecules with a unit speed have an average displacement of the root sign t within a time t.

A predator using this strategy to find prey would likely have to travel far and wide to be successful.

So before that, there is still a judgment on which villa in the community the alarm clock is in. This is another mathematical concept, Levi's flight.

It was Paul Pierre Levy, the mentor of the French mathematician Benhua Mandelbrot, who discovered Levi's flight. He first discovered that many random motions of life belong to Levi's flight, and at the same time contain a small part of Brownian motion.

This is a relatively complicated concept, so I won't explain it more, but there is an example that everyone should be familiar with. The flight trajectory of flies is the application of Levi's flight. This principle makes their flight trajectories elusive and helps flies. Avoiding predators and humans trying to knock their heads flat.

Levi's flight is a kind of fractal, that is to say, no matter how many times it is enlarged, it still looks similar to the original pattern.

More importantly, Levi's flight is a random walk, which means that its trajectory cannot be accurately predicted, just as ghostly as the pace of a fly.

Brownian motion has a characteristic, that is, the step length of each step is concentrated in one area, and the graph is a bell curve.

This is not the case with Levi's flight. In the Levi's flight diagram, the distance traveled per step follows the power law.

That is, most of the steps in the movement are short, but a small number of steps are very long.

【I am not good at mathematics, you are right】

[It's over, it's another lesson of listening to the scriptures]

【Damn it, can't survive in the wilderness without any knowledge of physics and mathematics? 】

Most of the viewers in the live broadcast room were basically stupefied when they heard this.

The different nature of the step size of Levi's flight and Brownian motion directly leads to the fact that Levi's flight is more efficient than Brownian motion.

With the same number of steps or distance taken, Levi's flight displacement is much larger than that of Brownian motion, and can explore a larger space.

This is critical for creatures that need to go wild in uncharted territory.

For example, marine predators such as sharks, when they know there is food nearby, use Brownian motion because Brownian motion helps with 'discs'—opening and emptying a small area of ​​hidden food.

But when food is scarce and new territory needs to be explored, marine predators abandon Brownian motion and adopt the strategy of Levi's flight.

[I wish I had said no earlier, it’s just luck]

[Summary: You should try your luck when shopping]

[I would like to say that Fang Shen's room is juxtaposed with Schrödinger's cat! 】

[Black tartary buckwheat tea was given to the anchor yacht*1——Although I don’t understand it, I like Fang Shen’s professionalism. 】

Behind the stone, Bi Fang and Harley, who was resting again, scanned the surroundings, wondering if there was any prey coming.

Meanwhile continue chatting with the audience.

In 2008, a research team from Yangguo and Ugland published a study in Nature: 55 different marine predators in the Atlantic and Pacific Oceans, including silky sharks, swordfish, blue marlin, yellowtail Fin tuna, sea turtles and penguins put on trackers to track their movements over 5,700 days.

After analyzing 12 million of their movements, a preference for Levy-style locomotion was found for most marine predators when food was scarce.

What's more interesting is that the distribution of prey, such as krill, also matches the characteristics of Levi's flight.

Not only that, the routes of amoebas, plankton, termites, bumblebees, large terrestrial herbivores, birds, primates, and aborigines in the soil have similar rules when foraging.

Levy flight appears to be a common law of living organisms in resource-scarce environments.

For nomadic animals, finding their next meal is not just about luck, it's about advanced mathematics.

With almost no knowledge of the distribution of prey, the efficiency of Levi's flight is far superior to that of Brownian motion. This may be the reason why they will switch to Levi's flight mode when they try their luck.

Therefore, biologists later proposed the Levy flight foraging hypothesis, which is used to summarize the coquettish movement of animals when they are resigned to their fate.

However, wild animals are resigned to their fate, which does not mean that Harley must also be resigned to their fate. We can help it realize that the probability of encountering prey in some places is greater, and just do Brownian motion at a few fixed locations to help it in the grassland. survive better.

[Referee, I report cheating on the other side! 】

[The report is invalid! 】

[What a bunch of cowhide, you are the first anchor I have ever seen to talk about mathematics in a serious manner outside the outdoor board]

[It’s really like learning mathematics, physics and chemistry well, and you won’t be afraid to travel all over the world. 】

[You think mathematics, physics and chemistry can't survive in the wilderness, but in fact it's just that you know too little, and you haven't learned enough (funny)]

After sitting behind the stone with Harley for a long time, finally at noon, Bi Fang encountered his first real prey on the grassland.

An ostrich!