In front of the narrow entrance of the cave, Bi Fang identified the animal tracks coming and going.
Some of these footprints have been preserved for a long time.
The surface of the African savannah in the dry season is dry and hard, leaving few footprints, unless it is a giant reptile like the Komodo dragon, whose sharp claws will leave a mark on the hard ground under the influence of its huge weight.
Make small holes.
Most of what everyone saw at the entrance of the cave were left behind during the wet season.
On the contrary, there are fresher footprints, paw prints, and hoof prints inside the cave.
"No large carnivores."
After watching for a long time, Bi Fang confirmed this.
Then he checked the surrounding environment and confirmed that there was only one entrance to the underground river within a certain range. He took Harley and hid behind a pile of rocks, preparing to wait and see.
Bifang sat on the ground next to the stone, polishing his spear.
"The quality of human life has greatly improved in recent decades - tall buildings, bustling streets, and beautiful night views are no longer new."
"The rapid development of technology has made our life tastes higher and higher. Things that were considered luxuries in the past can now be easily achieved."
“For three meals a day, we no longer just pursue satiety, but have higher quality requirements for taste. We pursue ‘good food’.”
"However, for the wild animals that also live on the earth, filling their stomachs is still their primary conflict."
"Herbivores or omnivores are relatively optimistic. Food sources are relatively abundant. As long as they are not born in a desert or a place 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 battle wits and courage with the prey, which is a double test of energy and physical strength. Moreover, even if the hunt is successful, the food obtained cannot be stored for a long time, and there is even a risk of being snatched away."
[Cheetah: Raise your hands in agreement]
[Cheetah: That’s right]
[Why @cheetah(doghead)]
[You can speak out if there is discrimination, let’s all do it together, 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 his body.
Perhaps because they are close to the water source, these plants growing in the rock gaps are all green, much more vibrant than the bright yellow hay seen on the grassland before.
"One of our main tasks in coming to the African savannah this time is to let Harley learn to hunt, so that he will not be so stupid that he can't even eat meat when he lives alone on the grassland."
"But different types of predators have different temperaments, tastes and physical conditions, and their hunting styles are naturally different. We also need to conduct demonstrations based on the characteristics of the animals themselves."
"For example, the differences in hunting styles between lions, tigers and wolves reflect the differences between cats and canines."
"Lions and tigers are very strong and agile, and the latter prefer to be solitary. Gray wolves are weaker in body and speed than lions and tigers, but living in groups greatly improves the gray wolf's hunting efficiency."
“When Canadian gray wolves are hunting bison, they will constantly use double-teaming and harassment tactics in the snow-covered natural environment to throw the bison herd into chaos and wait for opportunities to attack lone bison.”
"It's rare for someone to try to wipe out Yangcun on his own like Big Big Wolf did."
[This is a good example]
[Lao Fang can always give examples]
"Compared with wolves, tigers, as cats, are much more arrogant. Even among lions that are thought to hunt in groups, there are many male lions and a few female lions who like to move alone."
"Felines focus on ambush when hunting. They must be fast, ruthless and accurate. Even if the cheetah is the king of speed, it can often catch up with it through hard pursuit, but that is actually an additional cost. Being able to ambush is the best option."
"So, the focus of our demonstration is on ambush."
"However, a clever woman can't make a meal without rice. No matter what strategy is adopted, the predation operation needs a major prerequisite, that is, it must first be able to detect the prey, otherwise no matter how strong the predatory ability is, it is just talk on paper."
"For wild animals, the most natural foraging strategy is to simply follow Brownian motion and Levi's flight."
Brownian motion?
Levi flight?
When Bifang was talking about how to find prey, he suddenly heard a physical concept, and many viewers were a little confused.
【What the hell is Brownian motion?】
[Brownian motion is irregular, right? This seems to be inconsistent with Fang Shen’s thinking. Didn’t we always look for traces and traces in the past?]
[So, can anyone tell me, what is Levi Flying? 】
[I don’t read enough, tell me quickly]
"That's true, but the subject of finding traces, looking for traces, and finally identifying the direction is me - a human being."
"For animals, it's really a test of their brain capacity to clearly grasp these things."
"Most animals at the top of the food chain, such as lions, tigers, wolves, eagles, crocodiles, etc., actually mainly rely 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 see-through eyes."
"Raptors like eagles have a wide field of view and do not need to make great efforts to find food, but land animals such as lions and tigers have to consider the strategy of foraging."
"Brownian motion is the most natural method when the exact location of the prey is not known."
But before Bi Fang could finish explaining, the audience was 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? Did Fang Shen become confused after drinking it? 】
【Are you lying to me】
For a time, the barrage was filled with voices of doubt or inquiry.
"Hey, actually 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 an alarm clock is placed in a room on the second floor of a villa, and you sit in the living room on the first floor, can you accurately determine which room on the second floor the alarm clock is in simply relying on hearing?"
"I think most people can't do it. In the animal world with keen sense of smell, their sense of smell plays the same role as our 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. This is impossible to do in the world of sound."
[A little confused, but I feel like I’ve caught something again (face covering)]
[It seems to make sense]
[unclear]
"Everyone should be familiar with Brownian motion, which is the never-ending irregular 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 and has had a huge impact on human understanding of the universe."
"The behavior of many creatures in nature also obeys this point invisibly. Animals that perform Brownian motion are like coming to the second floor and randomly entering a room to search. And from a data perspective, this is the most efficient one.
way."
"Its step length obeys the normal distribution, just like a random walk, its step length and direction are discrete. Although Brownian motion and random walk are two concepts, they have each developed a different set of theories.
But the mathematical essence of the two is the same, and no matter which foraging strategy the predator uses, there is actually no difference in the efficiency of finding prey."
"But if a predator really does Brownian motion aimlessly like a headless fly, can it really find its prey very effectively?"
Bi Xiang asked the audience questions.
But you don’t need to answer to know that the answer is no.
"Mathematically it can be proved that Brownian motion is the same as the free diffusion of molecules. The molecules with unit speed only have an average displacement of square root t in time t."
"If a predator uses this method to find prey, it may have to travel across thousands of mountains and rivers to succeed."
"So before that, there is another way to determine which villa in the community the alarm clock is in. This is another mathematical concept, Levi's flight."
"The person who discovered Levi's flight was Paul Pierre Levi, the mentor of the French mathematician Benoit Mandelbrot. He first discovered that many random movements of life belong to Levi's flight, and also contain a small part of Brownian motion.
"
"This is a relatively complex concept, so I won't explain it in detail, but there is an example that everyone should be familiar with. The flight trajectory of flies is based on Levi's flight. This principle makes their flight trajectories elusive and helps flies
Avoiding predators and humans trying to knock their little heads off."
"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, Levi's flight is a random walk, which means that its trajectory cannot be accurately predicted and is as ghostly as the pace of a fly."
"Brownian motion has a characteristic, that is, the step length of each step is concentrated in a region, and the graph is a bell-shaped curve."
"That's not the case with Levi's flight. In the Levi's flight diagram, the distance traveled per step follows a power law."
"In other words, most of the steps in exercise are short, but a small number of steps are very long."
[I’m not good at math, you’re right]
[That’s it, another lesson on listening to the Book of Heaven]
[Damn it, without some knowledge of physics and mathematics, can’t you survive in the wilderness? 】
Most of the viewers in the live broadcast room were basically confused when they heard this.
"The different properties of the steps of Levi flight and Brownian motion directly lead to Levi flight being more efficient than Brownian motion."
"When walking the same number of steps or distance, Levi's flight displacement is much larger than that of Brownian motion, and it can explore a larger space."
"This is crucial for creatures that need to hunt in uncharted territory."
"For example, marine predators such as sharks use Brownian motion when they know there is food nearby, because Brownian motion helps 'disc' - opening and clearing a small area of hidden food."
"But when food is scarce and new territories need to be opened up, marine predators will abandon Brownian motion and adopt Levi's flight strategy."
[I wish I had said this earlier, it was just a matter of luck]
[Summary: Try your luck when shopping]
[I would like to call Fang Shen’s room juxtaposed with Schrödinger’s cat!]
[Black tartary buckwheat tea is presented to the anchor yacht*1 - Although I don’t understand, I give Fang Shen a thumbs up for his professionalism. 】
Behind the stone, Bifang and Harley, who was resting again, scanned the surroundings, wondering if any prey was coming.
All while continuing to chat with the audience.
"In 2008, a research team from China and China published a study in Nature: 55 different marine predators in the Atlantic and Pacific Ocean, including silky sharks, swordfish, blue marlin, yellow marlin,
Fin tuna, turtles and penguins were put on trackers to follow their movements over 5,700 days."
"After analyzing their movements 12 million times, the preference of most marine predators for Levitian movements when food is scarce was discovered."
"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 taken by amoebae, plankton, termites, bumblebees, large terrestrial herbivores, birds, primates, and indigenous people in the soil when foraging also follow similar patterns."
"Levy flight seems to be a common law for organisms to survive in resource-scarce environments."
"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, the efficiency of Levi's flight far exceeds that of Brownian motion. This may be the reason why they will switch to Levi's flight mode when trying their luck."
"Therefore, biologists later proposed Levi's flying foraging hypothesis to summarize the coquettish movements of animals when they leave their fate to their fate."
"However, just because wild animals resign themselves to fate, does not mean that Harley must also resign herself to fate. We can help it realize that the probability of encountering prey is greater in some places. Just do Brownian motion at several fixed locations to help it navigate the grassland.
Better to survive."
[Referee, I will report the opponent for cheating!]
[Report is invalid!]
[What a bunch of cowhide, you are the first anchor I have ever seen who talks about mathematics in a serious manner outside the outdoor board]
[If you really learn mathematics, physics and chemistry well, you won’t be afraid of traveling around the world.]
[You think mathematics, physics and chemistry can’t survive in the wilderness, but in fact you just know too little, and you’re not learned at all (funny)]
After sitting behind a rock with Harley for a long time, Bifang finally encountered his first real prey on the grassland at noon.