Chapter 861 Levi Flight
In front of the narrow cave entrance, Bifang identified the footprints of animals passing by.
Some of these footprints are quite old.
The surface of the African savannah is dry and hard during the dry season, and footprints are rarely left, unless it is a giant reptile like the Komodo dragon. Its sharp claws, under the effect of its huge weight, will leave a row of small holes in the hard ground.
Most of what everyone saw at the cave entrance were left over from the wet season.
There are some fresh footprints, claw prints and hoof prints in .
"There are no large carnivores."
After looking for a long time, Bifang confirmed this.
He then checked the surroundings and confirmed that there was only one entrance to this underground river within a certain range. He then took Harley and hid behind a pile of rocks, ready to wait for something to happen.
Bifang sat on the ground, leaning against the stone, sharpening his spear.
"The quality of human life has improved greatly in recent decades - tall buildings, bustling streets, and beautiful night scenes are no longer new things."
"The rapid development of technology has made our lifestyle more and more sophisticated. Things that were considered luxuries in the past can now be easily achieved."
"For three meals a day, we no longer just seek to fill our stomachs, but have higher quality requirements for taste. We pursue 'delicious food'."
"However, for wild animals that also live on Earth, filling their stomachs remains their primary concern."
"Herbivores and omnivores are still relatively optimistic, as their food sources are relatively abundant. As long as they are not born in a desert or a place like the Gobi Desert, there will always be something to eat."
"It's more demanding for carnivores, they have to hunt for food."
"During the hunting process, predators need to compete with their prey in wits and courage, which is a double test of their energy and physical strength. Moreover, even if the hunt is successful, the food obtained cannot be preserved for a long time and there is even a risk of it being stolen."
[Cheetah: Raise both hands to agree]
[Cheetah: That’s right]
【Why @Cheetah (dog head)】
[If there is discrimination, please speak up, everyone, hahahaha]
[Harley: What B netizen?]
Bifang carried the polished spear on his back and then looked for some plants with strong smells nearby to conceal his body.
Perhaps because they are close to the water source, the plants growing in the cracks of the rocks are all green, much more vibrant than the bright yellow hay seen on the grassland before.
"One of our main missions in coming to the African savannah this time is to teach Harley how to hunt, so that he won't be so stupid as to not even have enough meat to eat when he lives alone on the savannah."
"However, different types of predators have different temperaments, tastes and physical conditions, and naturally have different hunting styles. We also have to demonstrate according to the characteristics of the animals themselves."
"For example, the differences in hunting styles between lions, tigers and wolves reflect the differences between cats and dogs ."
"Lions and tigers are strong and agile, and the latter prefer to be alone; gray wolves are weaker in size and speed than lions and tigers, but living in groups greatly improves their hunting efficiency."
"When Canadian gray wolves hunt bison, they will constantly use double-teaming tactics to harass the herd in an ice-covered natural environment, causing confusion and waiting for opportunities to attack lone bison."
"It's rare for someone like Gray Wolf to want to wipe out the sheep village on his own."
This is a good example.
[Give an example that Lao Fang has always been able to do it]
"Compared with wolves, tigers, as cats, seem much more arrogant. Even among lions, which are generally considered to hunt in groups, there are many male lions and a few female lions who like to act alone."
"Cats hunt by ambush, which emphasizes speed, ruthlessness and accuracy. Even though cheetahs are the king of speed, they can often be caught by force, but that actually comes at an extra cost. Ambush is the best option."
"So, the focus of our demonstration is on ambush."
"But even a good cook cannot cook without rice. No matter what strategy is adopted, hunting action needs a major premise, that is, first of all, it needs to be able to find the prey. Otherwise, no matter how strong the hunting ability is, it is just a paper talk."
"For wild animals, the most natural foraging strategy is to simply follow Brownian motion and Lévy flight."
Brownian motion?
Levi flying?
When Bifang was talking about how to find prey, he suddenly heard a physics concept and many viewers were confused.
What is Brownian motion?
[ Brownian motion is irregular, right? This doesn't seem to match Fang Shen's thinking. Didn't we always look for traces and tracks before?]
[So, can anyone tell me what Levi Flight is? ]
[I don’t read much, tell me quickly]
"That's true, but the one who looks for traces, tracks, and ultimately determines the direction is me—a human being."
"For animals to grasp these things clearly is really a huge challenge for their brain capacity."
"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. If you can't see it, you can't see it. No animal has clairvoyance."
"Birds of prey like eagles have a wide field of vision and don't have to make a big move when it comes to finding food, but land animals like lions and tigers have to consider their foraging strategies."
"When the exact location of the prey is unknown, Brownian motion is the most natural method."
But before Bifang could finish explaining, the audience became even more confused.
[I'm not sure about lions and tigers, but don't wolves rely on smell? How come they rely on vision? ]
My cognition has been greatly challenged.
[Is the water in the underground river poisonous? Is Fang Shen confused after drinking it? ]
Are you lying to me?
For a moment, the barrage was full of questions and inquiries.
“Alas, in fact, people know too little about the world of smell.”
Bifang scratched his head. After all, the audience didn’t have the same keen sense of smell as him.
The gap in perception makes us feel like we are in two different worlds.
After thinking for a while, he gave an example that he thought was more appropriate.
"Let me put it this way. If there is an alarm clock in a room on the second floor of a villa, and you are sitting in the living room on the first floor, can you accurately determine which room on the second floor the alarm clock is in simply 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 hearing. They know the prey is on the second floor, but they don't know which room it is in. Moreover, the sense of smell is more ambiguous than hearing."
"If you stay in one place for a long time, you can create two strong smell sources, which is impossible in the world of sound."
[A little confused, but I feel like I have grasped something again (covering my face)]
[It seems to make sense]
【Unclear but powerful】
"Everyone should be familiar with Brownian motion, which is the endless irregular movement of particles suspended in liquid or gas, a continuous random process."
"Brownian motion may seem insignificant, but its discovery is a major development in physics and has had a huge impact on humanity's understanding of the universe."
"Many organisms in nature also behave in this way. Animals that perform Brownian motion are like those who come to the second floor and randomly enter a room to search. From a data perspective, this is the most efficient way."
"Its step length follows a normal distribution, just like a random walk, its step length and direction are discrete. Although Brownian motion and random walk are two concepts and have developed different theories, their mathematical essence is the same. No matter which foraging strategy the predator adopts, there is actually no difference in the efficiency of finding prey."
"But if the predator is really doing Brownian motion aimlessly like a headless fly, can it really find its prey effectively?"
Bi Xiang asked questions to the audience.
But you don’t need to answer to know that the answer is no.
"It can be proved mathematically that Brownian motion is just like the free diffusion of molecules. Molecules with unit speed have an average displacement of only square root t in time t."
"If a predator adopts this method to find prey, it may need to travel thousands of miles to succeed."
"So before that, there is another method to determine which villa in the community the alarm clock is in. This is another mathematical concept, Levi flight."
"The person who discovered Lévy flight was Paul Pierre Lévy, the mentor of French mathematician Benoit Mandelbrot. He was the first to discover that many random movements in life belong to Lévy flight, and also contain a small part of Brownian motion."
"This is a rather complex concept, so I won't explain it in detail, but there is one example that you should all be familiar with. The flight path of flies is based on Levy flight, which makes their flight paths unpredictable, helping them avoid predators and humans who want to crush their little heads."
"Levi's flight is a fractal, which means that no matter how many times it is magnified, it still looks similar to the original pattern."
"More importantly, Levy flight is a random walk, which means that its trajectory cannot be accurately predicted, just like the pace of a fly."
"One characteristic of Brownian motion is that the length of each step is concentrated in one area, and when plotted it is a bell-shaped curve."
"Levi flight is not like this. In the Levi flight diagram, the distance traveled per step conforms to the power law."
"That is, most steps during exercise are short, but a small number of steps are long."
[I am not good at math, you are right]
[It’s over. Another lesson of listening to the heavenly book]
[Damn it, without some knowledge of physics and mathematics, there is no way to survive in the wilderness? ]
Most of the audience in the live broadcast room were basically confused after hearing this.
"The different nature of the step lengths of Lévy flight and Brownian motion directly leads to the fact that Lévy flight is more efficient than Brownian motion."
"For the same number of steps or distance, the displacement of Lévy flight is much larger than that of Brownian motion, and it can explore a larger space."
"This is crucial for creatures that need to navigate uncharted territory."
"For example, marine predators such as sharks use Brownian motion when they know food is nearby because it helps to 'disc' - open and empty a small area of hidden food."
"But when food is scarce and they need to colonize new territories, marine predators abandon Brownian motion and adopt the strategy of Lévy flight."
[It would have been better if you said this earlier. It's just a matter of luck.]
[Summary: You should try your luck when shopping]
[I would like to put Fang Shen's room on par with Schrödinger's cat! ]
[A black bitter buckwheat tea is presented to the anchor yacht*1. ——Although I don’t understand, I give a thumbs up to Fang Shen’s professionalism. 】
Behind the rock, Bifang and Harley, who was resting again, looked around to see if there was any prey coming.
Meanwhile continue chatting with the audience.
"In 2008, a research team from China and the United States published a study in Nature: They put trackers on 55 different marine predators in the Atlantic and Pacific Oceans, including silky sharks, swordfish, blue marlin, yellowfin tuna, sea turtles and penguins, and tracked their movements for 5,700 days."
"After analyzing 12 million of their movements, we found that most marine predators showed a preference for Lévy-like movements when food is scarce."
"Even more interestingly, the distribution of prey, such as krill, also fits the profile of a Lévy flight."
"Not only that, the routes of amoeba, plankton, termites, bumblebees, large terrestrial herbivores, birds, primates, and indigenous peoples in the soil when foraging also follow similar patterns."
"Lévy flight appears to be a common law for organisms to survive in environments with scarce resources."
"For wandering animals, finding their next meal depends not only on luck but also on advanced mathematics."
"With almost no knowledge of the distribution of prey, Lévy flight is much more efficient than Brownian motion, which may be why they switch to Lévy flight mode when they are trying their luck."
"Therefore, biologists later proposed the Lévy flight hypothesis to summarize the coquettish movements of animals when they leave everything to fate."
"However, just because wild animals leave everything to fate doesn't mean Halley has to do the same. We can help it realize that the probability of encountering prey is higher in some places, and we can just do Brownian motion in a few fixed locations to help it survive better on the grassland."
[Referee, I report the opponent for cheating! ]
[The report is invalid ! ]
[You are such a boast! You are the first anchor I have ever seen who can seriously talk about mathematics outside of the outdoor board.]
【If you really learn math, physics and chemistry well, you won’t be afraid to travel around the world. 】
[You think that math, physics and chemistry are not enough to survive in the wilderness, but in fact it’s just that you know too little and haven’t learned them thoroughly (funny)]
After sitting behind a rock with Harley for a long time, Bifang finally encountered his first real prey on the grassland at noon.
An ostrich!
